WIP

core-traits/values.rs

@@ -19,11 +19,11 @@ use edn::types::Value;
 /// Declare a lazy static `ident` of type `Value::Keyword` with the given `namespace` and
 /// `name`.
 ///
-/// It may look surprising that we declare a new `lazy_static!` block rather than including
+/// It may look surprising to declare a new `lazy_static!` block rather than including
 /// invocations inside an existing `lazy_static!` block.  The latter cannot be done, since macros
-/// are expanded outside-in.  Looking at the `lazy_static!` source suggests that there is no harm in
-/// repeating that macro, since internally a multi-`static` block is expanded into many
-/// single-`static` blocks.
+/// will be expanded outside-in.  Looking at the `lazy_static!` source suggests that there is no
+/// harm in repeating that macro, since internally a multi-`static` block will be expanded into
+/// many single-`static` blocks.
 ///
 /// TODO: take just ":db.part/db" and define DB_PART_DB using "db.part" and "db".
 macro_rules! lazy_static_namespaced_keyword_value (

db/src/cache.rs

@@ -662,7 +662,7 @@ pub struct AttributeCaches {
     non_unique_reverse: BTreeMap<Entid, NonUniqueReverseAttributeCache>,
 }
 
-// TODO: if an entity or attribute is ever renumbered, the cache will need to be rebuilt.
+// TODO: if an entity or attribute is ever re-numbered, the cache will need to be rebuilt.
 impl AttributeCaches {
     //
     // These function names are brief and local.

docs/tutorial.md

@@ -0,0 +1,177 @@
+# Introduction
+
+Mentat is a transactional, relational storage system built on top of SQLite. The abstractions it offers allow you to easily tackle some things that are tricky in other storage systems:
+
+- Have multiple components share storage and collaborate.
+- Evolve schema.
+- Track change over time.
+- Synchronize data correctly.
+- Store data with rich, checked types.
+
+Mentat offers a programmatic Rust API for managing stores, retrieving data, and _transacting_ new data. It offers a Datalog-based query engine, with queries expressed in EDN, a rich textual data format similar to JSON. And it offers an EDN data format for transacting new data.
+
+This tutorial covers all of these APIs, along with defining vocabulary.
+
+We'll begin by introducing some concepts, and then we'll walk through some examples.
+
+
+## What does Mentat store?
+
+Depending on your perspective, Mentat looks like a relational store, a graph store, or a tuple store.
+
+Mentat stores relationships between _entities_ and other entities or _values_. An entity is related to other things by an _attribute_.
+
+All entities have an _entity ID_ (abbreviated to _entid_).
+
+Some entities additionally have an identifier called an _ident_, which is a keyword. That looks something like `:bookmark/title`.
+
+A value is a primitive piece of data. Mentat supports the following:
+
+* Strings
+* Long integers
+* Double-precision floating point numbers
+* Millisecond-precision timestamps
+* UUIDs
+* Booleans
+* Keywords (a special kind of string that we use for idents).
+
+There are two special kinds of entities: _attributes_ and _transactions_.
+
+Attributes are themselves entities with a particular set of properties that define their meaning. They have identifiers, so you can refer to them easily. They have a _value type_, which is the type of value Mentat expects to be on the right hand side of the relationship. And they have a _cardinality_ (whether one or many values can exist for a particular entity), whether values are _unique_, a documentation string, and some indexing options.
+
+An attribute looks something like this:
+
+```edn
+{:db/ident       :bookmark/title
+ :db/cardinality :db.cardinality/one
+ :db/valueType   :db.type/string
+ :db/fulltext    true
+ :db/doc         "The title of a bookmark."}
+```
+
+Transactions are special entities that can be described however you wish. By default they track the timestamp at which they were written.
+
+The relationship between an entity, an attribute, and a value, occurring in a _transaction_ (which is just another kind of entity!) — a tuple of five values — is called a _datom_.
+
+A single datom might look something like this:
+
+```
+       [:db/add          65536         :bookmark/title       "mozilla.org"              268435456]
+        ^                  ^              ^                     ^                         ^
+        \ Add or retract.  |              |                     |                         |
+                           \ The entity.  |                     |                         |
+                                          \ The attribute.      |                         |
+                                                                \ The value, a string.    |
+                                                                                          \ The transaction ID.
+```
+
+which is equivalent to saying "in transaction 268435456 we assert that entity 65536 is a bookmark with the title 'mozilla.org'".
+
+When we transact that — which means to add it as a fact to the store — Mentat also describes the transaction itself on our behalf:
+
+```edn
+       [:db/add 268435456 :db/txInstant "2018-01-25 20:07:04.408358 UTC" 268435456]
+```
+
+# A simple app
+
+Let's get started with some Rust code.
+
+First, the imports we'll need. The comments here briefly explain what each thing is.
+
+```rust
+// So you can define keywords with neater syntax.
+#[macro_use(kw)]
+extern crate mentat;
+
+use mentat::{
+    Store,          // A single database connection and in-memory metadata.
+}
+
+use mentat::vocabulary::attribute;      // Properties of attributes.
+```
+
+## Defining a simple vocabulary
+
+All data in Mentat — even the terms we used above, like `:db/cardinality` — are defined in the store itself. So that's where we start. In Rust, we define a _vocabulary definition_, and ask the store to ensure that it exists.
+
+```rust
+
+fn set_up(mut store: Store) -> Result<()> {
+    // Start a write transaction.
+    let mut in_progress = store.begin_transaction()?;
+
+    // Make sure the core vocabulary exists. This is good practice if a user,
+    // an external tool, or another component might have touched the file
+    // since you last wrote it.
+    in_progress.verify_core_schema()?;
+
+    // Make sure our vocabulary is installed, and install if necessary.
+    // This defines some attributes that we can use to describe people.
+    in_progress.ensure_vocabulary(&Definition {
+        name: kw!(:example/people),
+        version: 1,
+        attributes: vec![
+            (kw!(:person/name),
+             vocabulary::AttributeBuilder::default()
+               .value_type(ValueType::String)
+               .multival(true)
+               .build()),
+            (kw!(:person/age),
+             vocabulary::AttributeBuilder::default()
+               .value_type(ValueType::Long)
+               .multival(false)
+               .build()),
+            (kw!(:person/email),
+             vocabulary::AttributeBuilder::default()
+               .value_type(ValueType::String)
+               .multival(true)
+               .unique(attribute::Unique::Identity)
+               .build()),
+        ],
+    })?;
+
+    in_progress.commit()?;
+    Ok(())
+}
+```
+
+We open a store and configure its vocabulary like this:
+
+```rust
+let path = "/path/to/file.db";
+let store = Store::open(path)?;
+set_up(store)?;
+```
+
+If this code returns successfully, we're good to go.
+
+## Transactions
+
+You'll see in our `set_up` function that we begin and end a transaction, which we call `in_progress`. A read-only transaction is begun via `begin_read`. The resulting objects — `InProgress` and `InProgressRead` support various kinds of read and write operations. Transactions are automatically rolled back when dropped, so remember to call `commit`!
+
+## Adding some data
+
+There are two ways to add data to Mentat: programmatically or textually.
+
+The textual form accepts EDN, a simple relative of JSON that supports richer types and more flexible syntax. You saw this in the introduction. Here's an example:
+
+```rust
+in_progress.transact(r#"[
+    {:person/name "Alice"
+     :person/age 32
+     :person/email "alice@example.org"}
+]"#)?;
+```
+
+You can implicitly _upsert_ data when you have a unique attribute to use:
+
+```rust
+// Alice's age is now 33. Note that we don't need to find out an entid,
+// nor explicitly INSERT OR REPLACE or UPDATE OR INSERT or similar.
+in_progress.transact(r#"[
+    {:person/age 33
+     :person/email "alice@example.org"}
+]"#)?;
+```
+

edn/src/lib.rs

@@ -12,8 +12,8 @@ extern crate chrono;
 extern crate itertools;
 extern crate num;
 extern crate ordered_float;
-extern crate pretty;
 extern crate peg;
+extern crate pretty;
 extern crate uuid;
 
 #[cfg(feature = "serde_support")]
@@ -50,13 +50,11 @@ pub use types::{
 
 pub use symbols::{Keyword, NamespacedSymbol, PlainSymbol};
 
-use std::collections::{BTreeSet, BTreeMap, LinkedList};
+use std::collections::{BTreeMap, BTreeSet, LinkedList};
+use std::f64::{INFINITY, NAN, NEG_INFINITY};
 use std::iter::FromIterator;
-use std::f64::{NAN, INFINITY, NEG_INFINITY};
 
-use chrono::{
-    TimeZone,
-};
+use chrono::TimeZone;
 
 use entities::*;
 use query::FromValue;
@@ -70,7 +68,7 @@ use query::FromValue;
 // TODO: Support tagged elements
 // TODO: Support discard
 
-pub type ParseError = peg::error::ParseError<peg::str::LineCol>;
+pub type ParseErrorKind = peg::error::ParseError<peg::str::LineCol>;
 
 peg::parser!(pub grammar parse() for str {
 
@@ -525,4 +523,3 @@ peg::parser!(pub grammar parse() for str {
         / v:variable() { query::Binding::BindScalar(v) }
 
 });
-

edn/tests/tests.rs

@@ -23,7 +23,11 @@ use num::traits::{One, Zero};
 use ordered_float::OrderedFloat;
 
 use chrono::{TimeZone, Utc};
-use edn::{parse, symbols, types::{Span, SpannedValue, Value, ValueAndSpan}, utils, ParseError};
+use edn::{
+    parse, symbols,
+    types::{Span, SpannedValue, Value, ValueAndSpan},
+    utils, ParseErrorKind,
+};
 
 // Helper for making wrapped keywords with a namespace.
 fn k_ns(ns: &str, name: &str) -> Value {

public-traits/errors.rs

@@ -16,6 +16,12 @@ use std::collections::BTreeSet;
 use std::error::Error;
 
 use rusqlite;
+use failure::{
+    Backtrace,
+    Context,
+    Fail,
+};
++use std::fmt;
 use uuid;
 
 use edn;
@@ -39,8 +45,51 @@ use serde_json;
 
 pub type Result<T> = std::result::Result<T, MentatError>;
 
+#[derive(Debug)]
+pub struct MentatError(Box<Context<MentatErrorKind>>);
+
+impl Fail for MentatError {
+    #[inline]
+    fn cause(&self) -> Option<&Fail> {
+        self.0.cause()
+    }
+
+    #[inline]
+    fn backtrace(&self) -> Option<&Backtrace> {
+        self.0.backtrace()
+    }
+}
+
+impl fmt::Display for MentatError {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&*self.0, f)
+    }
+}
+
+impl MentatError {
+    #[inline]
+    pub fn kind(&self) -> &MentatErrorKind {
+        &*self.0.get_context()
+    }
+}
+
+impl From<MentatErrorKind> for MentatError {
+    #[inline]
+    fn from(kind: MentatErrorKind) -> MentatError {
+        MentatError(Box::new(Context::new(kind)))
+    }
+}
+
+impl From<Context<MentatErrorKind>> for MentatError {
+    #[inline]
+    fn from(inner: Context<MentatErrorKind>) -> MentatError {
+        MentatError(Box::new(inner))
+    }
+}
+
 #[derive(Debug, Fail)]
-pub enum MentatError {
+pub enum MentatErrorKind {
     #[fail(display = "bad uuid {}", _0)]
     BadUuid(String),
 
@@ -140,9 +189,67 @@ pub enum MentatError {
     SerializationError(#[cause] serde_json::Error),
 }
 
+impl From<std::io::Error> for MentatErrorKind {
+    fn from(error: std::io::Error) -> MentatErrorKind {
+        MentatErrorKind::IoError(error)
+    }
+}
+
+impl From<rusqlite::Error> for MentatErrorKind {
+    fn from(error: rusqlite::Error) -> MentatErrorKind {
+        MentatErrorKind::RusqliteError(error.to_string())
+    }
+}
+
+impl From<edn::ParseError> for MentatErrorKind {
+    fn from(error: edn::ParseError) -> MentatErrorKind {
+        MentatErrorKind::EdnParseError(error)
+    }
+}
+
+impl From<mentat_db::DbError> for MentatErrorKind {
+    fn from(error: mentat_db::DbError) -> MentatErrorKind {
+        MentatErrorKind::DbError(error)
+    }
+}
+
+impl From<mentat_query_algebrizer::AlgebrizerError> for MentatErrorKind {
+    fn from(error: mentat_query_algebrizer::AlgebrizerError) -> MentatErrorKind {
+        MentatErrorKind::AlgebrizerError(error)
+    }
+}
+
+impl From<mentat_query_projector::ProjectorError> for MentatErrorKind {
+    fn from(error: mentat_query_projector::ProjectorError) -> MentatErrorKind {
+        MentatErrorKind::ProjectorError(error)
+    }
+}
+
+impl From<mentat_query_pull::PullError> for MentatErrorKind {
+    fn from(error: mentat_query_pull::PullError) -> MentatErrorKind {
+        MentatErrorKind::PullError(error)
+    }
+}
+
+impl From<mentat_sql::SQLError> for MentatErrorKind {
+    fn from(error: mentat_sql::SQLError) -> MentatErrorKind {
+        MentatErrorKind::SQLError(error)
+    }
+}
+
+#[cfg(feature = "syncable")]
+impl From<mentat_tolstoy::TolstoyError> for MentatErrorKind {
+    fn from(error: mentat_tolstoy::TolstoyError) -> MentatErrorKind {
+        MentatErrorKind::TolstoyError(error)
+    }
+}
+
+// XXX reduce dupe if this isn't completely throwaway
+
+
 impl From<std::io::Error> for MentatError {
     fn from(error: std::io::Error) -> Self {
-        MentatError::IoError(error)
+        MentatError::from(error).into()
     }
 }
 
@@ -152,76 +259,76 @@ impl From<rusqlite::Error> for MentatError {
             Some(e) => e.to_string(),
             None => "".to_string(),
         };
-        MentatError::RusqliteError(error.to_string(), cause)
+        MentatError::from(error).into()
     }
 }
 
 impl From<uuid::Error> for MentatError {
     fn from(error: uuid::Error) -> Self {
-        MentatError::UuidError(error)
+        MentatError::from(error).into()
     }
 }
 
 impl From<edn::ParseError> for MentatError {
     fn from(error: edn::ParseError) -> Self {
-        MentatError::EdnParseError(error)
+        MentatError:from(error).into()
     }
 }
 
 impl From<DbError> for MentatError {
     fn from(error: DbError) -> Self {
-        MentatError::DbError(error)
+        MentatError::from(error).into()
     }
 }
 
 impl From<AlgebrizerError> for MentatError {
     fn from(error: AlgebrizerError) -> Self {
-        MentatError::AlgebrizerError(error)
+        MentatError::from(error).into()
     }
 }
 
 impl From<ProjectorError> for MentatError {
     fn from(error: ProjectorError) -> Self {
-        MentatError::ProjectorError(error)
+        MentatError::from(error).into()
     }
 }
 
 impl From<PullError> for MentatError {
     fn from(error: PullError) -> Self {
-        MentatError::PullError(error)
+        MentatError::from(error).into()
     }
 }
 
 impl From<SQLError> for MentatError {
     fn from(error: SQLError) -> Self {
-        MentatError::SQLError(error)
+        MentatError::from(error).into()
     }
 }
 
 #[cfg(feature = "syncable")]
 impl From<TolstoyError> for MentatError {
     fn from(error: TolstoyError) -> Self {
-        MentatError::TolstoyError(error)
+        MentatError::from(error).into()
     }
 }
 
 #[cfg(feature = "syncable")]
 impl From<serde_json::Error> for MentatError {
     fn from(error: serde_json::Error) -> Self {
-        MentatError::SerializationError(error)
+        MentatError::from(error).into()
     }
 }
 
 #[cfg(feature = "syncable")]
 impl From<hyper::Error> for MentatError {
     fn from(error: hyper::Error) -> Self {
-        MentatError::NetworkError(error)
+        MentatError::from(error).into()
     }
 }
 
 #[cfg(feature = "syncable")]
 impl From<http::uri::InvalidUri> for MentatError {
     fn from(error: http::uri::InvalidUri) -> Self {
-        MentatError::UriError(error)
+        MentatError::from(error).into()
     }
 }

query-algebrizer-traits/errors.rs

@@ -12,10 +12,60 @@ use std; // To refer to std::result::Result.
 
 use core_traits::{ValueType, ValueTypeSet};
 
-use edn::{ ParseError, query::PlainSymbol };
+use std::fmt;
+use failure::{
+    Backtrace,
+    Context,
+    Fail,
+};
+
+use edn::{query::PlainSymbol, ParseErrorKind};
 
 pub type Result<T> = std::result::Result<T, AlgebrizerError>;
 
+#[derive(Debug)]
+pub struct AlgebrizerError(Box<Context<AlgebrizerErrorKind>>);
+
+impl Fail for AlgebrizerError {
+    #[inline]
+    fn cause(&self) -> Option<&dyn Fail> {
+        self.0.cause()
+    }
+
+    #[inline]
+    fn backtrace(&self) -> Option<&Backtrace> {
+        self.0.backtrace()
+    }
+}
+
+impl fmt::Display for AlgebrizerError {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&*self.0, f)
+    }
+}
+
+impl AlgebrizerError {
+    #[inline]
+    pub fn kind(&self) -> &AlgebrizerErrorKind {
+        &*self.0.get_context()
+    }
+}
+
+impl From<AlgebrizerErrorKind> for AlgebrizerError {
+    #[inline]
+    fn from(kind: AlgebrizerErrorKind) -> AlgebrizerError {
+        AlgebrizerError(Box::new(Context::new(kind)))
+    }
+}
+
+impl From<Context<AlgebrizerErrorKind>> for AlgebrizerError {
+    #[inline]
+    fn from(inner: Context<AlgebrizerErrorKind>) -> AlgebrizerError {
+        AlgebrizerError(Box::new(inner))
+    }
+}
+
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum BindingError {
     NoBoundVariable,
@@ -40,7 +90,7 @@ pub enum BindingError {
 }
 
 #[derive(Clone, Debug, Eq, Fail, PartialEq)]
-pub enum AlgebrizerError {
+pub enum AlgebrizerErrorKind {
     #[fail(display = "{} var {} is duplicated", _0, _1)]
     DuplicateVariableError(PlainSymbol, &'static str),
 
@@ -107,11 +157,11 @@ pub enum AlgebrizerError {
     InvalidBinding(PlainSymbol, BindingError),
 
     #[fail(display = "{}", _0)]
-    EdnParseError(#[cause] ParseError),
+    EdnParseError(#[cause] ParseErrorKind),
 }
 
-impl From<ParseError> for AlgebrizerError {
-    fn from(error: ParseError) -> AlgebrizerError {
-        AlgebrizerError::EdnParseError(error)
+impl From<ParseErrorKind> for AlgebrizerError {
+    fn from(error: ParseErrorKind) -> AlgebrizerError {
+        AlgebrizerError::from(error).into()
     }
 }

query-algebrizer-traits/lib.rs

@@ -9,9 +9,6 @@
 // specific language governing permissions and limitations under the License.
 
 extern crate failure;
-#[macro_use]
-extern crate failure_derive;
-
 extern crate core_traits;
 extern crate edn;
 

query-algebrizer/src/clauses/convert.rs

@@ -16,7 +16,7 @@ use edn::query::{FnArg, NonIntegerConstant, Variable};
 
 use clauses::ConjoiningClauses;
 
-use query_algebrizer_traits::errors::{AlgebrizerError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, Result};
 
 use types::EmptyBecause;
 
@@ -62,11 +62,11 @@ impl ValueTypes for FnArg {
 
             &FnArg::Constant(NonIntegerConstant::BigInteger(_)) => {
                 // Not yet implemented.
-                bail!(AlgebrizerError::UnsupportedArgument)
+                bail!(AlgebrizerErrorKind::UnsupportedArgument)
             }
 
             // These don't make sense here. TODO: split FnArg into scalar and non-scalar…
-            &FnArg::Vector(_) | &FnArg::SrcVar(_) => bail!(AlgebrizerError::UnsupportedArgument),
+            &FnArg::Vector(_) | &FnArg::SrcVar(_) => bail!(AlgebrizerErrorKind::UnsupportedArgument),
 
             // These are all straightforward.
             &FnArg::Constant(NonIntegerConstant::Boolean(_)) => {
@@ -191,7 +191,7 @@ impl ConjoiningClauses {
             FnArg::Variable(in_var) => {
                 // TODO: technically you could ground an existing variable inside the query….
                 if !self.input_variables.contains(&in_var) {
-                    bail!(AlgebrizerError::UnboundVariable((*in_var.0).clone()))
+                    bail!(AlgebrizerErrorKind::UnboundVariable((*in_var.0).clone()))
                 }
                 match self.bound_value(&in_var) {
                     // The type is already known if it's a bound variable….
@@ -200,7 +200,7 @@ impl ConjoiningClauses {
                         // The variable is present in `:in`, but it hasn't yet been provided.
                         // This is a restriction we will eventually relax: we don't yet have a way
                         // to collect variables as part of a computed table or substitution.
-                        bail!(AlgebrizerError::UnboundVariable((*in_var.0).clone()))
+                        bail!(AlgebrizerErrorKind::UnboundVariable((*in_var.0).clone()))
                     }
                 }
             }
@@ -209,7 +209,7 @@ impl ConjoiningClauses {
             FnArg::Constant(NonIntegerConstant::BigInteger(_)) => unimplemented!(),
 
             // These don't make sense here.
-            FnArg::Vector(_) | FnArg::SrcVar(_) => bail!(AlgebrizerError::InvalidGroundConstant),
+            FnArg::Vector(_) | FnArg::SrcVar(_) => bail!(AlgebrizerErrorKind::InvalidGroundConstant),
 
             // These are all straightforward.
             FnArg::Constant(NonIntegerConstant::Boolean(x)) => {

query-algebrizer/src/clauses/fulltext.rs

@@ -18,7 +18,7 @@ use edn::query::{Binding, FnArg, NonIntegerConstant, SrcVar, VariableOrPlacehold
 
 use clauses::ConjoiningClauses;
 
-use query_algebrizer_traits::errors::{AlgebrizerError, BindingError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, BindingError, Result};
 
 use types::{
     Column, ColumnConstraint, DatomsColumn, DatomsTable, EmptyBecause, FulltextColumn,
@@ -31,7 +31,7 @@ impl ConjoiningClauses {
     #[allow(unused_variables)]
     pub(crate) fn apply_fulltext(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 3 {
-            bail!(AlgebrizerError::InvalidNumberOfArguments(
+            bail!(AlgebrizerErrorKind::InvalidNumberOfArguments(
                 where_fn.operator.clone(),
                 where_fn.args.len(),
                 3
@@ -40,7 +40,7 @@ impl ConjoiningClauses {
 
         if where_fn.binding.is_empty() {
             // The binding must introduce at least one bound variable.
-            bail!(AlgebrizerError::InvalidBinding(
+            bail!(AlgebrizerErrorKind::InvalidBinding(
                 where_fn.operator.clone(),
                 BindingError::NoBoundVariable
             ));
@@ -48,7 +48,7 @@ impl ConjoiningClauses {
 
         if !where_fn.binding.is_valid() {
             // The binding must not duplicate bound variables.
-            bail!(AlgebrizerError::InvalidBinding(
+            bail!(AlgebrizerErrorKind::InvalidBinding(
                 where_fn.operator.clone(),
                 BindingError::RepeatedBoundVariable
             ));
@@ -59,7 +59,7 @@ impl ConjoiningClauses {
             Binding::BindRel(bindings) => {
                 let bindings_count = bindings.len();
                 if bindings_count < 1 || bindings_count > 4 {
-                    bail!(AlgebrizerError::InvalidBinding(
+                    bail!(AlgebrizerErrorKind::InvalidBinding(
                         where_fn.operator.clone(),
                         BindingError::InvalidNumberOfBindings {
                             number: bindings.len(),
@@ -70,7 +70,7 @@ impl ConjoiningClauses {
                 bindings
             }
             Binding::BindScalar(_) | Binding::BindTuple(_) | Binding::BindColl(_) => {
-                bail!(AlgebrizerError::InvalidBinding(
+                bail!(AlgebrizerErrorKind::InvalidBinding(
                     where_fn.operator.clone(),
                     BindingError::ExpectedBindRel
                 ))
@@ -93,7 +93,7 @@ impl ConjoiningClauses {
         // TODO: process source variables.
         match args.next().unwrap() {
             FnArg::SrcVar(SrcVar::DefaultSrc) => {}
-            _ => bail!(AlgebrizerError::InvalidArgument(
+            _ => bail!(AlgebrizerErrorKind::InvalidArgument(
                 where_fn.operator.clone(),
                 "source variable",
                 0
@@ -116,12 +116,12 @@ impl ConjoiningClauses {
                 // TODO: allow non-constant attributes.
                 match self.bound_value(&v) {
                     Some(TypedValue::Ref(entid)) => Some(entid),
-                    Some(tv) => bail!(AlgebrizerError::InputTypeDisagreement(
+                    Some(tv) => bail!(AlgebrizerErrorKind::InputTypeDisagreement(
                         v.name().clone(),
                         ValueType::Ref,
                         tv.value_type()
                     )),
-                    None => bail!(AlgebrizerError::UnboundVariable((*v.0).clone())),
+                    None => bail!(AlgebrizerErrorKind::UnboundVariable((*v.0).clone())),
                 }
             }
             _ => None,
@@ -130,7 +130,7 @@ impl ConjoiningClauses {
         // An unknown ident, or an entity that isn't present in the store, or isn't a fulltext
         // attribute, is likely enough to be a coding error that we choose to bail instead of
         // marking the pattern as known-empty.
-        let a = a.ok_or(AlgebrizerError::InvalidArgument(
+        let a = a.ok_or(AlgebrizerErrorKind::InvalidArgument(
             where_fn.operator.clone(),
             "attribute",
             1,
@@ -139,7 +139,7 @@ impl ConjoiningClauses {
             schema
                 .attribute_for_entid(a)
                 .cloned()
-                .ok_or(AlgebrizerError::InvalidArgument(
+                .ok_or(AlgebrizerErrorKind::InvalidArgument(
                     where_fn.operator.clone(),
                     "attribute",
                     1,
@@ -190,7 +190,7 @@ impl ConjoiningClauses {
             FnArg::Variable(in_var) => {
                 match self.bound_value(&in_var) {
                     Some(t @ TypedValue::String(_)) => Either::Left(t),
-                    Some(_) => bail!(AlgebrizerError::InvalidArgument(
+                    Some(_) => bail!(AlgebrizerErrorKind::InvalidArgument(
                         where_fn.operator.clone(),
                         "string",
                         2
@@ -199,7 +199,7 @@ impl ConjoiningClauses {
                         // Regardless of whether we'll be providing a string later, or the value
                         // comes from a column, it must be a string.
                         if self.known_type(&in_var) != Some(ValueType::String) {
-                            bail!(AlgebrizerError::InvalidArgument(
+                            bail!(AlgebrizerErrorKind::InvalidArgument(
                                 where_fn.operator.clone(),
                                 "string",
                                 2
@@ -209,7 +209,7 @@ impl ConjoiningClauses {
                         if self.input_variables.contains(&in_var) {
                             // Sorry, we haven't implemented late binding.
                             // TODO: implement this.
-                            bail!(AlgebrizerError::UnboundVariable((*in_var.0).clone()))
+                            bail!(AlgebrizerErrorKind::UnboundVariable((*in_var.0).clone()))
                         } else {
                             // It must be bound earlier in the query. We already established that
                             // it must be a string column.
@@ -220,13 +220,13 @@ impl ConjoiningClauses {
                             {
                                 Either::Right(binding)
                             } else {
-                                bail!(AlgebrizerError::UnboundVariable((*in_var.0).clone()))
+                                bail!(AlgebrizerErrorKind::UnboundVariable((*in_var.0).clone()))
                             }
                         }
                     }
                 }
             }
-            _ => bail!(AlgebrizerError::InvalidArgument(
+            _ => bail!(AlgebrizerErrorKind::InvalidArgument(
                 where_fn.operator.clone(),
                 "string",
                 2
@@ -298,7 +298,7 @@ impl ConjoiningClauses {
 
             // We do not allow the score to be bound.
             if self.value_bindings.contains_key(var) || self.input_variables.contains(var) {
-                bail!(AlgebrizerError::InvalidBinding(
+                bail!(AlgebrizerErrorKind::InvalidBinding(
                     var.name(),
                     BindingError::UnexpectedBinding
                 ));

query-algebrizer/src/clauses/ground.rs

@@ -18,7 +18,7 @@ use clauses::{ConjoiningClauses, PushComputed};
 
 use clauses::convert::ValueConversion;
 
-use query_algebrizer_traits::errors::{AlgebrizerError, BindingError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, BindingError, Result};
 
 use types::{ComputedTable, EmptyBecause, SourceAlias, VariableColumn};
 
@@ -117,7 +117,7 @@ impl ConjoiningClauses {
 
     pub(crate) fn apply_ground(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 1 {
-            bail!(AlgebrizerError::InvalidNumberOfArguments(
+            bail!(AlgebrizerErrorKind::InvalidNumberOfArguments(
                 where_fn.operator.clone(),
                 where_fn.args.len(),
                 1
@@ -128,7 +128,7 @@ impl ConjoiningClauses {
 
         if where_fn.binding.is_empty() {
             // The binding must introduce at least one bound variable.
-            bail!(AlgebrizerError::InvalidBinding(
+            bail!(AlgebrizerErrorKind::InvalidBinding(
                 where_fn.operator.clone(),
                 BindingError::NoBoundVariable
             ));
@@ -136,7 +136,7 @@ impl ConjoiningClauses {
 
         if !where_fn.binding.is_valid() {
             // The binding must not duplicate bound variables.
-            bail!(AlgebrizerError::InvalidBinding(
+            bail!(AlgebrizerErrorKind::InvalidBinding(
                 where_fn.operator.clone(),
                 BindingError::RepeatedBoundVariable
             ));
@@ -154,7 +154,7 @@ impl ConjoiningClauses {
                 // Just the same, but we bind more than one column at a time.
                 if children.len() != places.len() {
                     // Number of arguments don't match the number of values. TODO: better error message.
-                    bail!(AlgebrizerError::GroundBindingsMismatch)
+                    bail!(AlgebrizerErrorKind::GroundBindingsMismatch)
                 }
                 for (place, arg) in places.into_iter().zip(children.into_iter()) {
                     self.apply_ground_place(schema, place, arg)? // TODO: short-circuit on impossible.
@@ -168,7 +168,7 @@ impl ConjoiningClauses {
             // are all in a single structure. That makes it substantially simpler!
             (Binding::BindColl(var), FnArg::Vector(children)) => {
                 if children.is_empty() {
-                    bail!(AlgebrizerError::InvalidGroundConstant)
+                    bail!(AlgebrizerErrorKind::InvalidGroundConstant)
                 }
 
                 // Turn a collection of arguments into a Vec of `TypedValue`s of the same type.
@@ -188,7 +188,7 @@ impl ConjoiningClauses {
                                     && !accumulated_types.is_unit()
                                 {
                                     // Values not all of the same type.
-                                    Some(Err(AlgebrizerError::InvalidGroundConstant.into()))
+                                    Some(Err(AlgebrizerErrorKind::InvalidGroundConstant.into()))
                                 } else {
                                     Some(Ok(tv))
                                 }
@@ -219,7 +219,7 @@ impl ConjoiningClauses {
 
             (Binding::BindRel(places), FnArg::Vector(rows)) => {
                 if rows.is_empty() {
-                    bail!(AlgebrizerError::InvalidGroundConstant)
+                    bail!(AlgebrizerErrorKind::InvalidGroundConstant)
                 }
 
                 // Grab the known types to which these args must conform, and track
@@ -243,7 +243,7 @@ impl ConjoiningClauses {
 
                 if expected_width == 0 {
                     // They can't all be placeholders.
-                    bail!(AlgebrizerError::InvalidGroundConstant)
+                    bail!(AlgebrizerErrorKind::InvalidGroundConstant)
                 }
 
                 // Accumulate values into `matrix` and types into `a_t_f_c`.
@@ -259,7 +259,7 @@ impl ConjoiningClauses {
                         FnArg::Vector(cols) => {
                             // Make sure that every row is the same length.
                             if cols.len() != full_width {
-                                bail!(AlgebrizerError::InvalidGroundConstant)
+                                bail!(AlgebrizerErrorKind::InvalidGroundConstant)
                             }
 
                             // TODO: don't accumulate twice.
@@ -297,12 +297,12 @@ impl ConjoiningClauses {
                                 let inserted = acc.insert(val.value_type());
                                 if inserted && !acc.is_unit() {
                                     // Heterogeneous types.
-                                    bail!(AlgebrizerError::InvalidGroundConstant)
+                                    bail!(AlgebrizerErrorKind::InvalidGroundConstant)
                                 }
                                 matrix.push(val);
                             }
                         }
-                        _ => bail!(AlgebrizerError::InvalidGroundConstant),
+                        _ => bail!(AlgebrizerErrorKind::InvalidGroundConstant),
                     }
                 }
 
@@ -329,7 +329,7 @@ impl ConjoiningClauses {
                 self.collect_named_bindings(schema, names, types, matrix);
                 Ok(())
             }
-            (_, _) => bail!(AlgebrizerError::InvalidGroundConstant),
+            (_, _) => bail!(AlgebrizerErrorKind::InvalidGroundConstant),
         }
     }
 }

query-algebrizer/src/clauses/inputs.rs

@@ -14,7 +14,7 @@ use core_traits::{TypedValue, ValueType};
 
 use edn::query::Variable;
 
-use query_algebrizer_traits::errors::{AlgebrizerError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, Result};
 
 /// Define the inputs to a query. This is in two parts: a set of values known now, and a set of
 /// types known now.
@@ -69,7 +69,7 @@ impl QueryInputs {
             let old = types.insert(var.clone(), t);
             if let Some(old) = old {
                 if old != t {
-                    bail!(AlgebrizerError::InputTypeDisagreement(var.name(), old, t));
+                    bail!(AlgebrizerErrorKind::InputTypeDisagreement(var.name(), old, t));
                 }
             }
         }

query-algebrizer/src/clauses/mod.rs

@@ -24,7 +24,7 @@ use mentat_core::counter::RcCounter;
 
 use edn::query::{Element, FindSpec, Keyword, PatternNonValuePlace, Pull, Variable, WhereClause};
 
-use query_algebrizer_traits::errors::{AlgebrizerError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, Result};
 
 use types::{
     Column, ColumnConstraint, ColumnIntersection, ComputedTable, DatomsColumn, DatomsTable,
@@ -1071,7 +1071,7 @@ impl ConjoiningClauses {
             let qa = self
                 .extracted_types
                 .get(&var)
-                .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()))?;
+                .ok_or_else(|| AlgebrizerErrorKind::UnboundVariable(var.name()))?;
             self.wheres.add_intersection(ColumnConstraint::HasTypes {
                 value: qa.0.clone(),
                 value_types: types,

query-algebrizer/src/clauses/not.rs

@@ -12,7 +12,7 @@ use edn::query::{ContainsVariables, NotJoin, UnifyVars};
 
 use clauses::ConjoiningClauses;
 
-use query_algebrizer_traits::errors::{AlgebrizerError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, Result};
 
 use types::{ColumnConstraint, ComputedTable};
 
@@ -35,7 +35,7 @@ impl ConjoiningClauses {
                 let col = self.column_bindings.get(&v).unwrap()[0].clone();
                 template.column_bindings.insert(v.clone(), vec![col]);
             } else {
-                bail!(AlgebrizerError::UnboundVariable(v.name()));
+                bail!(AlgebrizerErrorKind::UnboundVariable(v.name()));
             }
         }
 
@@ -89,7 +89,7 @@ mod testing {
 
     use clauses::{add_attribute, associate_ident, QueryInputs};
 
-    use query_algebrizer_traits::errors::AlgebrizerError;
+    use query_algebrizer_traits::errors::AlgebrizerErrorKind;
 
     use types::{
         ColumnAlternation, ColumnConstraint, ColumnConstraintOrAlternation, ColumnIntersection,
@@ -714,7 +714,7 @@ mod testing {
         let parsed = parse_find_string(query).expect("parse failed");
         let err = algebrize(known, parsed).expect_err("algebrization should have failed");
         match err {
-            AlgebrizerError::UnboundVariable(var) => {
+            AlgebrizerErrorKind::UnboundVariable(var) => {
                 assert_eq!(var, PlainSymbol("?x".to_string()));
             }
             x => panic!("expected Unbound Variable error, got {:?}", x),

query-algebrizer/src/clauses/predicate.rs

@@ -18,7 +18,7 @@ use clauses::ConjoiningClauses;
 
 use clauses::convert::ValueTypes;
 
-use query_algebrizer_traits::errors::{AlgebrizerError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, Result};
 
 use types::{ColumnConstraint, EmptyBecause, Inequality, QueryValue};
 
@@ -38,7 +38,7 @@ impl ConjoiningClauses {
         if let Some(op) = Inequality::from_datalog_operator(predicate.operator.0.as_str()) {
             self.apply_inequality(known, op, predicate)
         } else {
-            bail!(AlgebrizerError::UnknownFunction(predicate.operator.clone()))
+            bail!(AlgebrizerErrorKind::UnknownFunction(predicate.operator.clone()))
         }
     }
 
@@ -56,7 +56,7 @@ impl ConjoiningClauses {
             Some(value_type) => {
                 self.add_type_requirement(anno.variable.clone(), ValueTypeSet::of_one(value_type))
             }
-            None => bail!(AlgebrizerError::InvalidArgumentType(
+            None => bail!(AlgebrizerErrorKind::InvalidArgumentType(
                 PlainSymbol::plain("type"),
                 ValueTypeSet::any(),
                 2
@@ -76,7 +76,7 @@ impl ConjoiningClauses {
         predicate: Predicate,
     ) -> Result<()> {
         if predicate.args.len() != 2 {
-            bail!(AlgebrizerError::InvalidNumberOfArguments(
+            bail!(AlgebrizerErrorKind::InvalidNumberOfArguments(
                 predicate.operator.clone(),
                 predicate.args.len(),
                 2
@@ -97,7 +97,7 @@ impl ConjoiningClauses {
             .potential_types(known.schema, &left)?
             .intersection(&supported_types);
         if left_types.is_empty() {
-            bail!(AlgebrizerError::InvalidArgumentType(
+            bail!(AlgebrizerErrorKind::InvalidArgumentType(
                 predicate.operator.clone(),
                 supported_types,
                 0
@@ -108,7 +108,7 @@ impl ConjoiningClauses {
             .potential_types(known.schema, &right)?
             .intersection(&supported_types);
         if right_types.is_empty() {
-            bail!(AlgebrizerError::InvalidArgumentType(
+            bail!(AlgebrizerErrorKind::InvalidArgumentType(
                 predicate.operator.clone(),
                 supported_types,
                 1
@@ -160,7 +160,7 @@ impl ConjoiningClauses {
             left_v = self.resolve_ref_argument(known.schema, &predicate.operator, 0, left)?;
             right_v = self.resolve_ref_argument(known.schema, &predicate.operator, 1, right)?;
         } else {
-            bail!(AlgebrizerError::InvalidArgumentType(
+            bail!(AlgebrizerErrorKind::InvalidArgumentType(
                 predicate.operator.clone(),
                 supported_types,
                 0

query-algebrizer/src/clauses/resolve.rs

@@ -16,7 +16,7 @@ use edn::query::{FnArg, NonIntegerConstant, PlainSymbol};
 
 use clauses::ConjoiningClauses;
 
-use query_algebrizer_traits::errors::{AlgebrizerError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, Result};
 
 use types::{EmptyBecause, QueryValue};
 
@@ -41,14 +41,14 @@ impl ConjoiningClauses {
                     if v.value_type().is_numeric() {
                         Ok(QueryValue::TypedValue(v))
                     } else {
-                        bail!(AlgebrizerError::InputTypeDisagreement(var.name().clone(), ValueType::Long, v.value_type()))
+                        bail!(AlgebrizerErrorKind::InputTypeDisagreement(var.name().clone(), ValueType::Long, v.value_type()))
                     }
                 } else {
                     self.constrain_var_to_numeric(var.clone());
                     self.column_bindings
                         .get(&var)
                         .and_then(|cols| cols.first().map(|col| QueryValue::Column(col.clone())))
-                        .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()).into())
+                        .ok_or_else(|| AlgebrizerErrorKind::UnboundVariable(var.name()).into())
                 }
             },
             // Can't be an entid.
@@ -62,7 +62,7 @@ impl ConjoiningClauses {
             Constant(NonIntegerConstant::BigInteger(_)) |
             Vector(_) => {
                 self.mark_known_empty(EmptyBecause::NonNumericArgument);
-                bail!(AlgebrizerError::InvalidArgument(function.clone(), "numeric", position))
+                bail!(AlgebrizerErrorKind::InvalidArgument(function.clone(), "numeric", position))
             },
             Constant(NonIntegerConstant::Float(f)) => Ok(QueryValue::TypedValue(TypedValue::Double(f))),
         }
@@ -79,7 +79,7 @@ impl ConjoiningClauses {
         match arg {
             FnArg::Variable(var) => match self.bound_value(&var) {
                 Some(TypedValue::Instant(v)) => Ok(QueryValue::TypedValue(TypedValue::Instant(v))),
-                Some(v) => bail!(AlgebrizerError::InputTypeDisagreement(
+                Some(v) => bail!(AlgebrizerErrorKind::InputTypeDisagreement(
                     var.name().clone(),
                     ValueType::Instant,
                     v.value_type()
@@ -89,7 +89,7 @@ impl ConjoiningClauses {
                     self.column_bindings
                         .get(&var)
                         .and_then(|cols| cols.first().map(|col| QueryValue::Column(col.clone())))
-                        .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()).into())
+                        .ok_or_else(|| AlgebrizerErrorKind::UnboundVariable(var.name()).into())
                 }
             },
             Constant(NonIntegerConstant::Instant(v)) => {
@@ -107,7 +107,7 @@ impl ConjoiningClauses {
             | Constant(NonIntegerConstant::BigInteger(_))
             | Vector(_) => {
                 self.mark_known_empty(EmptyBecause::NonInstantArgument);
-                bail!(AlgebrizerError::InvalidArgumentType(
+                bail!(AlgebrizerErrorKind::InvalidArgumentType(
                     function.clone(),
                     ValueType::Instant.into(),
                     position
@@ -136,14 +136,14 @@ impl ConjoiningClauses {
                     self.column_bindings
                         .get(&var)
                         .and_then(|cols| cols.first().map(|col| QueryValue::Column(col.clone())))
-                        .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()).into())
+                        .ok_or_else(|| AlgebrizerErrorKind::UnboundVariable(var.name()).into())
                 }
             }
             EntidOrInteger(i) => Ok(QueryValue::TypedValue(TypedValue::Ref(i))),
             IdentOrKeyword(i) => schema
                 .get_entid(&i)
                 .map(|known_entid| QueryValue::Entid(known_entid.into()))
-                .ok_or_else(|| AlgebrizerError::UnrecognizedIdent(i.to_string()).into()),
+                .ok_or_else(|| AlgebrizerErrorKind::UnrecognizedIdent(i.to_string()).into()),
             Constant(NonIntegerConstant::Boolean(_))
             | Constant(NonIntegerConstant::Float(_))
             | Constant(NonIntegerConstant::Text(_))
@@ -153,7 +153,7 @@ impl ConjoiningClauses {
             | SrcVar(_)
             | Vector(_) => {
                 self.mark_known_empty(EmptyBecause::NonEntityArgument);
-                bail!(AlgebrizerError::InvalidArgumentType(
+                bail!(AlgebrizerErrorKind::InvalidArgumentType(
                     function.clone(),
                     ValueType::Ref.into(),
                     position
@@ -188,7 +188,7 @@ impl ConjoiningClauses {
                     .column_bindings
                     .get(&var)
                     .and_then(|cols| cols.first().map(|col| QueryValue::Column(col.clone())))
-                    .ok_or_else(|| AlgebrizerError::UnboundVariable(var.name()).into()),
+                    .ok_or_else(|| AlgebrizerErrorKind::UnboundVariable(var.name()).into()),
             },
             EntidOrInteger(i) => Ok(QueryValue::PrimitiveLong(i)),
             IdentOrKeyword(_) => unimplemented!(), // TODO

query-algebrizer/src/clauses/tx_log_api.rs

@@ -14,7 +14,7 @@ use edn::query::{Binding, FnArg, SrcVar, VariableOrPlaceholder, WhereFn};
 
 use clauses::ConjoiningClauses;
 
-use query_algebrizer_traits::errors::{AlgebrizerError, BindingError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, BindingError, Result};
 
 use types::{
     Column, ColumnConstraint, DatomsTable, Inequality, QualifiedAlias, QueryValue, SourceAlias,
@@ -40,7 +40,7 @@ impl ConjoiningClauses {
     // transactions that impact one of the given attributes.
     pub(crate) fn apply_tx_ids(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 3 {
-            bail!(AlgebrizerError::InvalidNumberOfArguments(
+            bail!(AlgebrizerErrorKind::InvalidNumberOfArguments(
                 where_fn.operator.clone(),
                 where_fn.args.len(),
                 3
@@ -49,7 +49,7 @@ impl ConjoiningClauses {
 
         if where_fn.binding.is_empty() {
             // The binding must introduce at least one bound variable.
-            bail!(AlgebrizerError::InvalidBinding(
+            bail!(AlgebrizerErrorKind::InvalidBinding(
                 where_fn.operator.clone(),
                 BindingError::NoBoundVariable
             ));
@@ -57,7 +57,7 @@ impl ConjoiningClauses {
 
         if !where_fn.binding.is_valid() {
             // The binding must not duplicate bound variables.
-            bail!(AlgebrizerError::InvalidBinding(
+            bail!(AlgebrizerErrorKind::InvalidBinding(
                 where_fn.operator.clone(),
                 BindingError::RepeatedBoundVariable
             ));
@@ -68,7 +68,7 @@ impl ConjoiningClauses {
             Binding::BindRel(bindings) => {
                 let bindings_count = bindings.len();
                 if bindings_count != 1 {
-                    bail!(AlgebrizerError::InvalidBinding(
+                    bail!(AlgebrizerErrorKind::InvalidBinding(
                         where_fn.operator.clone(),
                         BindingError::InvalidNumberOfBindings {
                             number: bindings_count,
@@ -83,7 +83,7 @@ impl ConjoiningClauses {
             }
             Binding::BindColl(v) => v,
             Binding::BindScalar(_) | Binding::BindTuple(_) => {
-                bail!(AlgebrizerError::InvalidBinding(
+                bail!(AlgebrizerErrorKind::InvalidBinding(
                     where_fn.operator.clone(),
                     BindingError::ExpectedBindRelOrBindColl
                 ))
@@ -95,7 +95,7 @@ impl ConjoiningClauses {
         // TODO: process source variables.
         match args.next().unwrap() {
             FnArg::SrcVar(SrcVar::DefaultSrc) => {}
-            _ => bail!(AlgebrizerError::InvalidArgument(
+            _ => bail!(AlgebrizerErrorKind::InvalidArgument(
                 where_fn.operator.clone(),
                 "source variable",
                 0
@@ -150,7 +150,7 @@ impl ConjoiningClauses {
 
     pub(crate) fn apply_tx_data(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 2 {
-            bail!(AlgebrizerError::InvalidNumberOfArguments(
+            bail!(AlgebrizerErrorKind::InvalidNumberOfArguments(
                 where_fn.operator.clone(),
                 where_fn.args.len(),
                 2
@@ -159,7 +159,7 @@ impl ConjoiningClauses {
 
         if where_fn.binding.is_empty() {
             // The binding must introduce at least one bound variable.
-            bail!(AlgebrizerError::InvalidBinding(
+            bail!(AlgebrizerErrorKind::InvalidBinding(
                 where_fn.operator.clone(),
                 BindingError::NoBoundVariable
             ));
@@ -167,7 +167,7 @@ impl ConjoiningClauses {
 
         if !where_fn.binding.is_valid() {
             // The binding must not duplicate bound variables.
-            bail!(AlgebrizerError::InvalidBinding(
+            bail!(AlgebrizerErrorKind::InvalidBinding(
                 where_fn.operator.clone(),
                 BindingError::RepeatedBoundVariable
             ));
@@ -178,7 +178,7 @@ impl ConjoiningClauses {
             Binding::BindRel(bindings) => {
                 let bindings_count = bindings.len();
                 if bindings_count < 1 || bindings_count > 5 {
-                    bail!(AlgebrizerError::InvalidBinding(
+                    bail!(AlgebrizerErrorKind::InvalidBinding(
                         where_fn.operator.clone(),
                         BindingError::InvalidNumberOfBindings {
                             number: bindings.len(),
@@ -189,7 +189,7 @@ impl ConjoiningClauses {
                 bindings
             }
             Binding::BindScalar(_) | Binding::BindTuple(_) | Binding::BindColl(_) => {
-                bail!(AlgebrizerError::InvalidBinding(
+                bail!(AlgebrizerErrorKind::InvalidBinding(
                     where_fn.operator.clone(),
                     BindingError::ExpectedBindRel
                 ))
@@ -217,7 +217,7 @@ impl ConjoiningClauses {
         // TODO: process source variables.
         match args.next().unwrap() {
             FnArg::SrcVar(SrcVar::DefaultSrc) => {}
-            _ => bail!(AlgebrizerError::InvalidArgument(
+            _ => bail!(AlgebrizerErrorKind::InvalidArgument(
                 where_fn.operator.clone(),
                 "source variable",
                 0

query-algebrizer/src/clauses/where_fn.rs

@@ -12,7 +12,7 @@ use edn::query::WhereFn;
 
 use clauses::ConjoiningClauses;
 
-use query_algebrizer_traits::errors::{AlgebrizerError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, Result};
 
 use Known;
 
@@ -32,7 +32,7 @@ impl ConjoiningClauses {
             "ground" => self.apply_ground(known, where_fn),
             "tx-data" => self.apply_tx_data(known, where_fn),
             "tx-ids" => self.apply_tx_ids(known, where_fn),
-            _ => bail!(AlgebrizerError::UnknownFunction(where_fn.operator.clone())),
+            _ => bail!(AlgebrizerErrorKind::UnknownFunction(where_fn.operator.clone())),
         }
     }
 }

query-algebrizer/src/lib.rs

@@ -32,7 +32,7 @@ use mentat_core::counter::RcCounter;
 
 use edn::query::{Element, FindSpec, Limit, Order, ParsedQuery, SrcVar, Variable, WhereClause};
 
-use query_algebrizer_traits::errors::{AlgebrizerError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, Result};
 
 pub use clauses::{QueryInputs, VariableBindings};
 
@@ -229,7 +229,7 @@ fn validate_and_simplify_order(
 
                 // Fail if the var isn't bound by the query.
                 if !cc.column_bindings.contains_key(&var) {
-                    bail!(AlgebrizerError::UnboundVariable(var.name()))
+                    bail!(AlgebrizerErrorKind::UnboundVariable(var.name()))
                 }
 
                 // Otherwise, determine if we also need to order by type…
@@ -263,7 +263,7 @@ fn simplify_limit(mut query: AlgebraicQuery) -> Result<AlgebraicQuery> {
                 Some(TypedValue::Long(n)) => {
                     if n <= 0 {
                         // User-specified limits should always be natural numbers (> 0).
-                        bail!(AlgebrizerError::InvalidLimit(
+                        bail!(AlgebrizerErrorKind::InvalidLimit(
                             n.to_string(),
                             ValueType::Long
                         ))
@@ -273,7 +273,7 @@ fn simplify_limit(mut query: AlgebraicQuery) -> Result<AlgebraicQuery> {
                 }
                 Some(val) => {
                     // Same.
-                    bail!(AlgebrizerError::InvalidLimit(
+                    bail!(AlgebrizerErrorKind::InvalidLimit(
                         format!("{:?}", val),
                         val.value_type()
                     ))
@@ -375,7 +375,7 @@ impl FindQuery {
 
             for var in parsed.in_vars.into_iter() {
                 if !set.insert(var.clone()) {
-                    bail!(AlgebrizerError::DuplicateVariableError(var.name(), ":in"));
+                    bail!(AlgebrizerErrorKind::DuplicateVariableError(var.name(), ":in"));
                 }
             }
 
@@ -387,7 +387,7 @@ impl FindQuery {
 
             for var in parsed.with.into_iter() {
                 if !set.insert(var.clone()) {
-                    bail!(AlgebrizerError::DuplicateVariableError(var.name(), ":with"));
+                    bail!(AlgebrizerErrorKind::DuplicateVariableError(var.name(), ":with"));
                 }
             }
 
@@ -397,7 +397,7 @@ impl FindQuery {
         // Make sure that if we have `:limit ?x`, `?x` appears in `:in`.
         if let Limit::Variable(ref v) = parsed.limit {
             if !in_vars.contains(v) {
-                bail!(AlgebrizerError::UnknownLimitVar(v.name()));
+                bail!(AlgebrizerErrorKind::UnknownLimitVar(v.name()));
             }
         }
 

query-algebrizer/src/validate.rs

@@ -12,7 +12,7 @@ use std::collections::BTreeSet;
 
 use edn::query::{ContainsVariables, NotJoin, OrJoin, UnifyVars, Variable};
 
-use query_algebrizer_traits::errors::{AlgebrizerError, Result};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, Result};
 
 /// In an `or` expression, every mentioned var is considered 'free'.
 /// In an `or-join` expression, every var in the var list is 'required'.
@@ -47,7 +47,7 @@ pub(crate) fn validate_or_join(or_join: &OrJoin) -> Result<()> {
                 let template = clauses.next().unwrap().collect_mentioned_variables();
                 for clause in clauses {
                     if template != clause.collect_mentioned_variables() {
-                        bail!(AlgebrizerError::NonMatchingVariablesInOrClause)
+                        bail!(AlgebrizerErrorKind::NonMatchingVariablesInOrClause)
                     }
                 }
                 Ok(())
@@ -58,7 +58,7 @@ pub(crate) fn validate_or_join(or_join: &OrJoin) -> Result<()> {
             let var_set: BTreeSet<Variable> = vars.iter().cloned().collect();
             for clause in &or_join.clauses {
                 if !var_set.is_subset(&clause.collect_mentioned_variables()) {
-                    bail!(AlgebrizerError::NonMatchingVariablesInOrClause)
+                    bail!(AlgebrizerErrorKind::NonMatchingVariablesInOrClause)
                 }
             }
             Ok(())
@@ -74,7 +74,7 @@ pub(crate) fn validate_not_join(not_join: &NotJoin) -> Result<()> {
             // The joined vars must each appear somewhere in the clause's mentioned variables.
             let var_set: BTreeSet<Variable> = vars.iter().cloned().collect();
             if !var_set.is_subset(&not_join.collect_mentioned_variables()) {
-                bail!(AlgebrizerError::NonMatchingVariablesInNotClause)
+                bail!(AlgebrizerErrorKind::NonMatchingVariablesInNotClause)
             }
             Ok(())
         }

query-algebrizer/tests/ground.rs

@@ -24,7 +24,7 @@ use mentat_core::Schema;
 
 use edn::query::{Keyword, PlainSymbol, Variable};
 
-use query_algebrizer_traits::errors::{AlgebrizerError, BindingError};
+use query_algebrizer_traits::errors::{AlgebrizerErrorKind, BindingError};
 
 use mentat_query_algebrizer::{ComputedTable, Known, QueryInputs};
 
@@ -297,7 +297,7 @@ fn test_ground_coll_heterogeneous_types() {
     let q = r#"[:find ?x :where [?x _ ?v] [(ground [false 8.5]) [?v ...]]]"#;
     let schema = prepopulated_schema();
     let known = Known::for_schema(&schema);
-    assert_eq!(bails(known, &q), AlgebrizerError::InvalidGroundConstant);
+    assert_eq!(bails(known, &q), AlgebrizerErrorKind::InvalidGroundConstant);
 }
 
 #[test]
@@ -305,7 +305,7 @@ fn test_ground_rel_heterogeneous_types() {
     let q = r#"[:find ?x :where [?x _ ?v] [(ground [[false] [5]]) [[?v]]]]"#;
     let schema = prepopulated_schema();
     let known = Known::for_schema(&schema);
-    assert_eq!(bails(known, &q), AlgebrizerError::InvalidGroundConstant);
+    assert_eq!(bails(known, &q), AlgebrizerErrorKind::InvalidGroundConstant);
 }
 
 #[test]
@@ -315,7 +315,7 @@ fn test_ground_tuple_duplicate_vars() {
     let known = Known::for_schema(&schema);
     assert_eq!(
         bails(known, &q),
-        AlgebrizerError::InvalidBinding(
+        AlgebrizerErrorKind::InvalidBinding(
             PlainSymbol::plain("ground"),
             BindingError::RepeatedBoundVariable
         )
@@ -329,7 +329,7 @@ fn test_ground_rel_duplicate_vars() {
     let known = Known::for_schema(&schema);
     assert_eq!(
         bails(known, &q),
-        AlgebrizerError::InvalidBinding(
+        AlgebrizerErrorKind::InvalidBinding(
             PlainSymbol::plain("ground"),
             BindingError::RepeatedBoundVariable
         )
@@ -343,7 +343,7 @@ fn test_ground_nonexistent_variable_invalid() {
     let known = Known::for_schema(&schema);
     assert_eq!(
         bails(known, &q),
-        AlgebrizerError::UnboundVariable(PlainSymbol::plain("?v"))
+        AlgebrizerErrorKind::UnboundVariable(PlainSymbol::plain("?v"))
     );
 }
 
@@ -362,6 +362,6 @@ fn test_unbound_input_variable_invalid() {
 
     assert_eq!(
         bails_with_inputs(known, &q, i),
-        AlgebrizerError::UnboundVariable(PlainSymbol::plain("?x"))
+        AlgebrizerErrorKind::UnboundVariable(PlainSymbol::plain("?x"))
     );
 }

query-algebrizer/tests/predicate.rs

@@ -22,7 +22,7 @@ use mentat_core::{DateTime, Schema, Utc};
 
 use edn::query::{Keyword, PlainSymbol, Variable};
 
-use query_algebrizer_traits::errors::AlgebrizerError;
+use query_algebrizer_traits::errors::AlgebrizerErrorKind;
 
 use mentat_query_algebrizer::{EmptyBecause, Known, QueryInputs};
 
@@ -75,7 +75,7 @@ fn test_instant_predicates_require_instants() {
                     [(> ?t "2017-06-16T00:56:41.257Z")]]"#;
     assert_eq!(
         bails(known, query),
-        AlgebrizerError::InvalidArgumentType(
+        AlgebrizerErrorKind::InvalidArgumentType(
             PlainSymbol::plain(">"),
             ValueTypeSet::of_numeric_and_instant_types(),
             1
@@ -88,7 +88,7 @@ fn test_instant_predicates_require_instants() {
                     [(> "2017-06-16T00:56:41.257Z", ?t)]]"#;
     assert_eq!(
         bails(known, query),
-        AlgebrizerError::InvalidArgumentType(
+        AlgebrizerErrorKind::InvalidArgumentType(
             PlainSymbol::plain(">"),
             ValueTypeSet::of_numeric_and_instant_types(),
             0

query-projector-traits/aggregates.rs

@@ -16,7 +16,7 @@ use mentat_query_algebrizer::{ColumnName, ConjoiningClauses, VariableColumn};
 
 use mentat_query_sql::{ColumnOrExpression, Expression, Name, ProjectedColumn};
 
-use errors::{ProjectorError, Result};
+use errors::{ProjectorErrorKind, Result};
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub enum SimpleAggregationOp {
@@ -60,7 +60,7 @@ impl SimpleAggregationOp {
     pub fn is_applicable_to_types(&self, possibilities: ValueTypeSet) -> Result<ValueType> {
         use self::SimpleAggregationOp::*;
         if possibilities.is_empty() {
-            bail!(ProjectorError::CannotProjectImpossibleBinding(*self))
+            bail!(ProjectorErrorKind::CannotProjectImpossibleBinding(*self))
         }
 
         match self {
@@ -73,7 +73,7 @@ impl SimpleAggregationOp {
                     // The mean of a set of numeric values will always, for our purposes, be a double.
                     Ok(ValueType::Double)
                 } else {
-                    bail!(ProjectorError::CannotApplyAggregateOperationToTypes(
+                    bail!(ProjectorErrorKind::CannotApplyAggregateOperationToTypes(
                         *self,
                         possibilities
                     ))
@@ -88,7 +88,7 @@ impl SimpleAggregationOp {
                         Ok(ValueType::Long)
                     }
                 } else {
-                    bail!(ProjectorError::CannotApplyAggregateOperationToTypes(
+                    bail!(ProjectorErrorKind::CannotApplyAggregateOperationToTypes(
                         *self,
                         possibilities
                     ))
@@ -111,7 +111,7 @@ impl SimpleAggregationOp {
 
                         // These types are unordered.
                         Keyword | Ref | Uuid => {
-                            bail!(ProjectorError::CannotApplyAggregateOperationToTypes(
+                            bail!(ProjectorErrorKind::CannotApplyAggregateOperationToTypes(
                                 *self,
                                 possibilities
                             ))
@@ -129,7 +129,7 @@ impl SimpleAggregationOp {
                             Ok(ValueType::Long)
                         }
                     } else {
-                        bail!(ProjectorError::CannotApplyAggregateOperationToTypes(
+                        bail!(ProjectorErrorKind::CannotApplyAggregateOperationToTypes(
                             *self,
                             possibilities
                         ))

query-projector-traits/errors.rs

@@ -15,14 +15,60 @@ use rusqlite;
 use core_traits::ValueTypeSet;
 use db_traits::errors::DbError;
 use edn::query::PlainSymbol;
+use failure::{ Backtrace, Context, Fail, };
+use std::fmt;
 use query_pull_traits::errors::PullError;
 
 use aggregates::SimpleAggregationOp;
 
 pub type Result<T> = std::result::Result<T, ProjectorError>;
 
+#[derive(Debug)]
+pub struct ProjectorError(Box<Context<ProjectorErrorKind>>);
+
+impl Fail for ProjectorError {
+    #[inline]
+    fn cause(&self) -> Option<&Fail> {
+        self.0.cause()
+    }
+
+    #[inline]
+    fn backtrace(&self) -> Option<&Backtrace> {
+        self.0.backtrace()
+    }
+}
+
+impl fmt::Display for ProjectorError {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&*self.0, f)
+    }
+}
+
+impl ProjectorError {
+    #[inline]
+    pub fn kind(&self) -> &ProjectorErrorKind {
+        &*self.0.get_context()
+    }
+}
+
+impl From<ProjectorErrorKind> for ProjectorError {
+    #[inline]
+    fn from(kind: ProjectorErrorKind) -> ProjectorError {
+        ProjectorError(Box::new(Context::new(kind)))
+    }
+}
+
+impl From<Context<ProjectorErrorKind>> for ProjectorError {
+    #[inline]
+    fn from(inner: Context<ProjectorErrorKind>) -> ProjectorError {
+        ProjectorError(Box::new(inner))
+    }
+}
+
+
 #[derive(Debug, Fail)]
-pub enum ProjectorError {
+pub enum ProjectorErrorKind {
     /// We're just not done yet.  Message that the feature is recognized but not yet
     /// implemented.
     #[fail(display = "not yet implemented: {}", _0)]
@@ -70,6 +116,24 @@ pub enum ProjectorError {
     PullError(#[cause] PullError),
 }
 
+impl From<rusqlite::Error> for ProjectorErrorKind {
+    fn from(error: rusqlite::Error) -> ProjectorErrorKind {
+        ProjectorErrorKind::from(error).into()
+    }
+}
+
+impl From<mentat_db::DbError> for ProjectorErrorKind {
+    fn from(error: mentat_db::DbError) -> ProjectorErrorKind {
+        ProjectorErrorKind::from(error).into()
+    }
+}
+
+impl From<mentat_query_pull::PullError> for ProjectorErrorKind {
+    fn from(error: mentat_query_pull::PullError) -> ProjectorErrorKind {
+        ProjectorErrorKind::from(error).into()
+    }
+}
+
 impl From<rusqlite::Error> for ProjectorError {
     fn from(error: rusqlite::Error) -> ProjectorError {
         ProjectorError::RusqliteError(error.to_string())

query-projector-traits/tests/aggregates.rs

@@ -101,9 +101,9 @@ fn test_the_without_max_or_min() {
     // … when we look at the projection list, we cannot reconcile the types.
     let projection = query_projection(&schema, &algebrized);
     assert!(projection.is_err());
-    use query_projector_traits::errors::ProjectorError;
+    use query_projector_traits::errors::ProjectorErrorKind;
     match projection.err().expect("expected failure") {
-        ProjectorError::InvalidProjection(s) => {
+        ProjectorErrorKind::InvalidProjection(s) => {
             assert_eq!(s.as_str(), "Warning: used `the` without `min` or `max`.");
         }
         _ => panic!(),

query-projector/src/binding_tuple.rs

@@ -10,7 +10,7 @@
 
 use core_traits::Binding;
 
-use query_projector_traits::errors::{ProjectorError, Result};
+use query_projector_traits::errors::{ProjectorErrorKind, Result};
 
 /// A `BindingTuple` is any type that can accommodate a Mentat tuple query result of fixed length.
 ///
@@ -27,7 +27,7 @@ impl BindingTuple for Vec<Binding> {
             None => Ok(None),
             Some(vec) => {
                 if expected != vec.len() {
-                    Err(ProjectorError::UnexpectedResultsTupleLength(
+                    Err(ProjectorErrorKind::UnexpectedResultsTupleLength(
                         expected,
                         vec.len(),
                     ))
@@ -43,13 +43,13 @@ impl BindingTuple for Vec<Binding> {
 impl BindingTuple for (Binding,) {
     fn from_binding_vec(expected: usize, vec: Option<Vec<Binding>>) -> Result<Option<Self>> {
         if expected != 1 {
-            return Err(ProjectorError::UnexpectedResultsTupleLength(1, expected));
+            return Err(ProjectorErrorKind::UnexpectedResultsTupleLength(1, expected));
         }
         match vec {
             None => Ok(None),
             Some(vec) => {
                 if expected != vec.len() {
-                    Err(ProjectorError::UnexpectedResultsTupleLength(
+                    Err(ProjectorErrorKind::UnexpectedResultsTupleLength(
                         expected,
                         vec.len(),
                     ))
@@ -65,13 +65,13 @@ impl BindingTuple for (Binding,) {
 impl BindingTuple for (Binding, Binding) {
     fn from_binding_vec(expected: usize, vec: Option<Vec<Binding>>) -> Result<Option<Self>> {
         if expected != 2 {
-            return Err(ProjectorError::UnexpectedResultsTupleLength(2, expected));
+            return Err(ProjectorErrorKind::UnexpectedResultsTupleLength(2, expected));
         }
         match vec {
             None => Ok(None),
             Some(vec) => {
                 if expected != vec.len() {
-                    Err(ProjectorError::UnexpectedResultsTupleLength(
+                    Err(ProjectorErrorKind::UnexpectedResultsTupleLength(
                         expected,
                         vec.len(),
                     ))
@@ -87,13 +87,13 @@ impl BindingTuple for (Binding, Binding) {
 impl BindingTuple for (Binding, Binding, Binding) {
     fn from_binding_vec(expected: usize, vec: Option<Vec<Binding>>) -> Result<Option<Self>> {
         if expected != 3 {
-            return Err(ProjectorError::UnexpectedResultsTupleLength(3, expected));
+            return Err(ProjectorErrorKind::UnexpectedResultsTupleLength(3, expected));
         }
         match vec {
             None => Ok(None),
             Some(vec) => {
                 if expected != vec.len() {
-                    Err(ProjectorError::UnexpectedResultsTupleLength(
+                    Err(ProjectorErrorKind::UnexpectedResultsTupleLength(
                         expected,
                         vec.len(),
                     ))
@@ -113,13 +113,13 @@ impl BindingTuple for (Binding, Binding, Binding) {
 impl BindingTuple for (Binding, Binding, Binding, Binding) {
     fn from_binding_vec(expected: usize, vec: Option<Vec<Binding>>) -> Result<Option<Self>> {
         if expected != 4 {
-            return Err(ProjectorError::UnexpectedResultsTupleLength(4, expected));
+            return Err(ProjectorErrorKind::UnexpectedResultsTupleLength(4, expected));
         }
         match vec {
             None => Ok(None),
             Some(vec) => {
                 if expected != vec.len() {
-                    Err(ProjectorError::UnexpectedResultsTupleLength(
+                    Err(ProjectorErrorKind::UnexpectedResultsTupleLength(
                         expected,
                         vec.len(),
                     ))
@@ -140,13 +140,13 @@ impl BindingTuple for (Binding, Binding, Binding, Binding) {
 impl BindingTuple for (Binding, Binding, Binding, Binding, Binding) {
     fn from_binding_vec(expected: usize, vec: Option<Vec<Binding>>) -> Result<Option<Self>> {
         if expected != 5 {
-            return Err(ProjectorError::UnexpectedResultsTupleLength(5, expected));
+            return Err(ProjectorErrorKind::UnexpectedResultsTupleLength(5, expected));
         }
         match vec {
             None => Ok(None),
             Some(vec) => {
                 if expected != vec.len() {
-                    Err(ProjectorError::UnexpectedResultsTupleLength(
+                    Err(ProjectorErrorKind::UnexpectedResultsTupleLength(
                         expected,
                         vec.len(),
                     ))
@@ -170,13 +170,13 @@ impl BindingTuple for (Binding, Binding, Binding, Binding, Binding) {
 impl BindingTuple for (Binding, Binding, Binding, Binding, Binding, Binding) {
     fn from_binding_vec(expected: usize, vec: Option<Vec<Binding>>) -> Result<Option<Self>> {
         if expected != 6 {
-            return Err(ProjectorError::UnexpectedResultsTupleLength(6, expected));
+            return Err(ProjectorErrorKind::UnexpectedResultsTupleLength(6, expected));
         }
         match vec {
             None => Ok(None),
             Some(vec) => {
                 if expected != vec.len() {
-                    Err(ProjectorError::UnexpectedResultsTupleLength(
+                    Err(ProjectorErrorKind::UnexpectedResultsTupleLength(
                         expected,
                         vec.len(),
                     ))

query-projector/src/lib.rs

@@ -69,7 +69,7 @@ use projectors::{
 
 pub use relresult::{RelResult, StructuredRelResult};
 
-use query_projector_traits::errors::{ProjectorError, Result};
+use query_projector_traits::errors::{ProjectorErrorKind, Result};
 
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct QueryOutput {
@@ -275,43 +275,43 @@ impl QueryResults {
     pub fn into_scalar(self) -> Result<Option<Binding>> {
         match self {
             QueryResults::Scalar(o) => Ok(o),
-            QueryResults::Coll(_) => bail!(ProjectorError::UnexpectedResultsType("coll", "scalar")),
+            QueryResults::Coll(_) => bail!(ProjectorErrorKind::UnexpectedResultsType("coll", "scalar")),
             QueryResults::Tuple(_) => {
-                bail!(ProjectorError::UnexpectedResultsType("tuple", "scalar"))
+                bail!(ProjectorErrorKind::UnexpectedResultsType("tuple", "scalar"))
             }
-            QueryResults::Rel(_) => bail!(ProjectorError::UnexpectedResultsType("rel", "scalar")),
+            QueryResults::Rel(_) => bail!(ProjectorErrorKind::UnexpectedResultsType("rel", "scalar")),
         }
     }
 
     pub fn into_coll(self) -> Result<Vec<Binding>> {
         match self {
             QueryResults::Scalar(_) => {
-                bail!(ProjectorError::UnexpectedResultsType("scalar", "coll"))
+                bail!(ProjectorErrorKind::UnexpectedResultsType("scalar", "coll"))
             }
             QueryResults::Coll(c) => Ok(c),
-            QueryResults::Tuple(_) => bail!(ProjectorError::UnexpectedResultsType("tuple", "coll")),
-            QueryResults::Rel(_) => bail!(ProjectorError::UnexpectedResultsType("rel", "coll")),
+            QueryResults::Tuple(_) => bail!(ProjectorErrorKind::UnexpectedResultsType("tuple", "coll")),
+            QueryResults::Rel(_) => bail!(ProjectorErrorKind::UnexpectedResultsType("rel", "coll")),
         }
     }
 
     pub fn into_tuple(self) -> Result<Option<Vec<Binding>>> {
         match self {
             QueryResults::Scalar(_) => {
-                bail!(ProjectorError::UnexpectedResultsType("scalar", "tuple"))
+                bail!(ProjectorErrorKind::UnexpectedResultsType("scalar", "tuple"))
             }
-            QueryResults::Coll(_) => bail!(ProjectorError::UnexpectedResultsType("coll", "tuple")),
+            QueryResults::Coll(_) => bail!(ProjectorErrorKind::UnexpectedResultsType("coll", "tuple")),
             QueryResults::Tuple(t) => Ok(t),
-            QueryResults::Rel(_) => bail!(ProjectorError::UnexpectedResultsType("rel", "tuple")),
+            QueryResults::Rel(_) => bail!(ProjectorErrorKind::UnexpectedResultsType("rel", "tuple")),
         }
     }
 
     pub fn into_rel(self) -> Result<RelResult<Binding>> {
         match self {
             QueryResults::Scalar(_) => {
-                bail!(ProjectorError::UnexpectedResultsType("scalar", "rel"))
+                bail!(ProjectorErrorKind::UnexpectedResultsType("scalar", "rel"))
             }
-            QueryResults::Coll(_) => bail!(ProjectorError::UnexpectedResultsType("coll", "rel")),
-            QueryResults::Tuple(_) => bail!(ProjectorError::UnexpectedResultsType("tuple", "rel")),
+            QueryResults::Coll(_) => bail!(ProjectorErrorKind::UnexpectedResultsType("coll", "rel")),
+            QueryResults::Tuple(_) => bail!(ProjectorErrorKind::UnexpectedResultsType("tuple", "rel")),
             QueryResults::Rel(r) => Ok(r),
         }
     }
@@ -526,7 +526,7 @@ fn test_into_tuple() {
     );
 
     match query_output.clone().into_tuple() {
-        Err(ProjectorError::UnexpectedResultsTupleLength(expected, got)) => {
+        Err(ProjectorErrorKind::UnexpectedResultsTupleLength(expected, got)) => {
             assert_eq!((expected, got), (3, 2));
         }
         // This forces the result type.
@@ -548,7 +548,7 @@ fn test_into_tuple() {
     }
 
     match query_output.clone().into_tuple() {
-        Err(ProjectorError::UnexpectedResultsTupleLength(expected, got)) => {
+        Err(ProjectorErrorKind::UnexpectedResultsTupleLength(expected, got)) => {
             assert_eq!((expected, got), (3, 2));
         }
         // This forces the result type.

query-projector/src/project.rs

@@ -30,7 +30,7 @@ use query_projector_traits::aggregates::{
     projected_column_for_simple_aggregate, SimpleAggregation,
 };
 
-use query_projector_traits::errors::{ProjectorError, Result};
+use query_projector_traits::errors::{ProjectorErrorKind, Result};
 
 use projectors::Projector;
 
@@ -98,14 +98,14 @@ fn candidate_type_column(
             let type_name = VariableColumn::VariableTypeTag(var.clone()).column_name();
             (ColumnOrExpression::Column(alias), type_name)
         })
-        .ok_or_else(|| ProjectorError::UnboundVariable(var.name()).into())
+        .ok_or_else(|| ProjectorErrorKind::UnboundVariable(var.name()).into())
 }
 
 fn cc_column(cc: &ConjoiningClauses, var: &Variable) -> Result<QualifiedAlias> {
     cc.column_bindings
         .get(var)
         .and_then(|cols| cols.get(0).cloned())
-        .ok_or_else(|| ProjectorError::UnboundVariable(var.name()).into())
+        .ok_or_else(|| ProjectorErrorKind::UnboundVariable(var.name()).into())
 }
 
 fn candidate_column(cc: &ConjoiningClauses, var: &Variable) -> Result<(ColumnOrExpression, Name)> {
@@ -187,13 +187,13 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
         match e {
             &Element::Variable(ref var) => {
                 if outer_variables.contains(var) {
-                    bail!(ProjectorError::InvalidProjection(format!(
+                    bail!(ProjectorErrorKind::InvalidProjection(format!(
                         "Duplicate variable {} in query.",
                         var
                     )));
                 }
                 if corresponded_variables.contains(var) {
-                    bail!(ProjectorError::InvalidProjection(format!(
+                    bail!(ProjectorErrorKind::InvalidProjection(format!(
                         "Can't project both {} and `(the {})` from a query.",
                         var, var
                     )));
@@ -201,13 +201,13 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
             }
             &Element::Corresponding(ref var) => {
                 if outer_variables.contains(var) {
-                    bail!(ProjectorError::InvalidProjection(format!(
+                    bail!(ProjectorErrorKind::InvalidProjection(format!(
                         "Can't project both {} and `(the {})` from a query.",
                         var, var
                     )));
                 }
                 if corresponded_variables.contains(var) {
-                    bail!(ProjectorError::InvalidProjection(format!(
+                    bail!(ProjectorErrorKind::InvalidProjection(format!(
                         "`(the {})` appears twice in query.",
                         var
                     )));
@@ -344,7 +344,7 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
                     i += 1;
                 } else {
                     // TODO: complex aggregates.
-                    bail!(ProjectorError::NotYetImplemented(
+                    bail!(ProjectorErrorKind::NotYetImplemented(
                         "complex aggregates".into()
                     ));
                 }
@@ -355,7 +355,7 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
     match (min_max_count, corresponded_variables.len()) {
         (0, 0) | (_, 0) => {}
         (0, _) => {
-            bail!(ProjectorError::InvalidProjection(
+            bail!(ProjectorErrorKind::InvalidProjection(
                 "Warning: used `the` without `min` or `max`.".to_string()
             ));
         }
@@ -363,7 +363,7 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
             // This is the success case!
         }
         (n, c) => {
-            bail!(ProjectorError::AmbiguousAggregates(n, c));
+            bail!(ProjectorErrorKind::AmbiguousAggregates(n, c));
         }
     }
 
@@ -466,7 +466,7 @@ pub(crate) fn project_elements<'a, I: IntoIterator<Item = &'a Element>>(
             let type_name = VariableColumn::VariableTypeTag(var.clone()).column_name();
             if !already_inner {
                 let type_col = query.cc.extracted_types.get(&var).cloned().ok_or_else(|| {
-                    ProjectorError::NoTypeAvailableForVariable(var.name().clone())
+                    ProjectorErrorKind::NoTypeAvailableForVariable(var.name().clone())
                 })?;
                 inner_projection.push(ProjectedColumn(
                     ColumnOrExpression::Column(type_col),

query-pull-traits/errors.rs

@@ -12,10 +12,50 @@ use std; // To refer to std::result::Result.
 
 use db_traits::errors::DbError;
 
+use failure::{ Backtrace, Context, Fail, };
+
 use core_traits::Entid;
 
+use std::fmt;
+
 pub type Result<T> = std::result::Result<T, PullError>;
 
+#[derive(Debug)]
+pub struct PullErrorKind(Box<Context<PullErrorKind>>);
+
+impl Fail for PullError {
+    #[inline]
+    fn cause(&self) -> Option<&dyn Fail> {
+        self.0.cause()
+    }
+
+    #[inline]
+    fn backtrace(&self) -> Option<&Backtrace> {
+        self.0.backtrace()
+    }
+}
+
+impl fmt::Display for PullError {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&*self.0, f)
+    }
+}
+
+impl PullError {
+    #[inline]
+    pub fn kind(&self) -> &PullErrorKind {
+        &*self.0.get_context()
+    }
+}
+
+impl From<PullErrorKind> for PullError {
+    #[inline]
+    fn from(kind: PullErrorKind) -> PullError {
+        PullErrorKind(Box::new(Context::new(kind)))
+    }
+}
+
 #[derive(Debug, Fail)]
 pub enum PullError {
     #[fail(display = "attribute {:?} has no name", _0)]
@@ -28,8 +68,13 @@ pub enum PullError {
     DbError(#[cause] DbError),
 }
 
-impl From<DbError> for PullError {
-    fn from(error: DbError) -> PullError {
-        PullError::DbError(error)
+impl From<DbError> for PullErrorKind {
+    fn from(error: DbError) -> PullErrorKind {
+        PullErrorKind::DbError(error)
+    }
+}
+impl From<DbError> for PullError {
+    fn from(error: DbError) -> PullError {
+        PullErrorKind::from(error).into()
     }
 }

query-pull-traits/lib.rs

@@ -9,8 +9,6 @@
 // specific language governing permissions and limitations under the License.
 
 extern crate failure;
-#[macro_use]
-extern crate failure_derive;
 
 extern crate core_traits;
 extern crate db_traits;

query-pull/src/lib.rs

@@ -77,7 +77,7 @@ use mentat_db::cache;
 
 use edn::query::{NamedPullAttribute, PullAttributeSpec, PullConcreteAttribute};
 
-use query_pull_traits::errors::{PullError, Result};
+use query_pull_traits::errors::{PullErrorKind, Result};
 
 type PullResults = BTreeMap<Entid, ValueRc<StructuredMap>>;
 
@@ -149,7 +149,7 @@ impl Puller {
             schema
                 .get_ident(*i)
                 .map(|ident| ValueRc::new(ident.clone()))
-                .ok_or_else(|| PullError::UnnamedAttribute(*i))
+                .ok_or_else(|| PullErrorKind::UnnamedAttribute(*i))
         };
 
         let mut names: BTreeMap<Entid, ValueRc<Keyword>> = Default::default();
@@ -177,7 +177,7 @@ impl Puller {
                         &PullConcreteAttribute::Ident(ref i) if i.as_ref() == db_id.as_ref() => {
                             // We only allow :db/id once.
                             if db_id_alias.is_some() {
-                                Err(PullError::RepeatedDbId)?
+                                Err(PullErrorKind::RepeatedDbId)?
                             }
                             db_id_alias = Some(alias.unwrap_or_else(|| db_id.to_value_rc()));
                         }

sql-traits/errors.rs

@@ -8,8 +8,54 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
+use failure::{ Backtrace, Context, Fail, };
+use std::fmt;
+
+#[derive(Debug)]
+pub struct SQLError(Box<Context<SQLErrorKind>>);
+
+impl Fail for SQLError {
+    #[inline]
+    fn cause(&self) -> Option<&dyn Fail> {
+        self.0.cause()
+    }
+
+    #[inline]
+    fn backtrace(&self) -> Option<&Backtrace> {
+        self.0.backtrace()
+    }
+}
+
+impl fmt::Display for SQLError {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&*self.0, f)
+    }
+}
+
+impl SQLError {
+    #[inline]
+    pub fn kind(&self) -> &SQLErrorKind {
+        &*self.0.get_context()
+    }
+}
+
+impl From<SQLErrorKind> for SQLError {
+    #[inline]
+    fn from(kind: SQLErrorKind) -> SQLError {
+        SQLError(Box::new(Context::new(kind)))
+    }
+}
+
+impl From<Context<SQLErrorKind>> for SQLError {
+    #[inline]
+    fn from(inner: Context<SQLErrorKind>) -> SQLError {
+        SQLError(Box::new(inner))
+    }
+}
+
 #[derive(Debug, Fail)]
-pub enum SQLError {
+pub enum SQLErrorKind {
     #[fail(display = "invalid parameter name: {}", _0)]
     InvalidParameterName(String),
 

sql-traits/lib.rs

@@ -9,7 +9,5 @@
 // specific language governing permissions and limitations under the License.
 
 extern crate failure;
-#[macro_use]
-extern crate failure_derive;
 
 pub mod errors;

sql/src/lib.rs

@@ -18,14 +18,13 @@ extern crate mentat_core;
 extern crate sql_traits;
 
 use std::rc::Rc;
-
 use std::collections::HashMap;
 
 use ordered_float::OrderedFloat;
 
 use core_traits::TypedValue;
 
-use sql_traits::errors::{BuildQueryResult, SQLError};
+use sql_traits::errors::{BuildQueryResult, SQLErrorKind};
 
 use mentat_core::{ToMicros, ValueRc};
 
@@ -194,7 +193,7 @@ impl QueryBuilder for SQLiteQueryBuilder {
         // Do some validation first.
         // This is not free, but it's probably worth it for now.
         if !name.chars().all(|c| char::is_alphanumeric(c) || c == '_') {
-            return Err(SQLError::InvalidParameterName(name.to_string()));
+            return Err(SQLErrorKind::InvalidParameterName(name.to_string()));
         }
 
         if name.starts_with(self.arg_prefix.as_str())
@@ -203,7 +202,7 @@ impl QueryBuilder for SQLiteQueryBuilder {
                 .skip(self.arg_prefix.len())
                 .all(char::is_numeric)
         {
-            return Err(SQLError::BindParamCouldBeGenerated(name.to_string()));
+            return Err(SQLErrorKind::BindParamCouldBeGenerated(name.to_string()));
         }
 
         self.push_sql("$");

src/conn.rs

@@ -36,7 +36,7 @@ use mentat_query_pull::{pull_attributes_for_entities, pull_attributes_for_entity
 
 use mentat_transaction::{CacheAction, CacheDirection, InProgress, InProgressRead, Metadata};
 
-use public_traits::errors::{MentatError, Result};
+use public_traits::errors::{MentatErrorKind, Result};
 
 use mentat_transaction::query::{
     lookup_value_for_attribute, lookup_values_for_attribute, q_explain, q_once, q_prepare,
@@ -340,7 +340,7 @@ impl Conn {
             attribute_entid = metadata
                 .schema
                 .attribute_for_ident(&attribute)
-                .ok_or_else(|| MentatError::UnknownAttribute(attribute.to_string()))?
+                .ok_or_else(|| MentatErrorKind::UnknownAttribute(attribute.to_string()))?
                 .1
                 .into();
         }
@@ -404,12 +404,16 @@ mod tests {
         let t = format!("[[:db/add {} :db.schema/attribute \"tempid\"]]", next + 1);
 
         match conn.transact(&mut sqlite, t.as_str()) {
-            Err(MentatError::DbError(e)) => {
-                assert_eq!(
-                    e.kind(),
-                    ::db_traits::errors::DbErrorKind::UnallocatedEntid(next + 1)
-                );
+            Err(e) => {
+                match e.kind() {
+                    &MentatErrorKind::DbError(ref e) => {
+                        assert_eq!(e.kind(), ::mentat_db::DbErrorKind::UnallocatedEntid(next + 1));
                     }
+                    x => {
+                        panic!("expected db error, got {:?}", x);
+                    }
+                }
+            },
             x => panic!("expected db error, got {:?}", x),
         }
 
@@ -434,12 +438,15 @@ mod tests {
         let t = format!("[[:db/add {} :db.schema/attribute \"tempid\"]]", next);
 
         match conn.transact(&mut sqlite, t.as_str()) {
-            Err(MentatError::DbError(e)) => {
-                // All this, despite this being the ID we were about to allocate!
-                assert_eq!(
-                    e.kind(),
-                    ::db_traits::errors::DbErrorKind::UnallocatedEntid(next)
-                );
+            Err(e) => {
+                match e.kind() {
+                    &MentatErrorKind::DbError(ref e) => {
+                        assert_eq!(e.kind(), ::mentat_db::DbErrorKind::UnallocatedEntid(next + 1));
+                    }
+                    x => {
+                        panic!("expected db error, got {:?}", x);
+                    }
+                }
             }
             x => panic!("expected db error, got {:?}", x),
         }
@@ -642,8 +649,8 @@ mod tests {
 
         // Bad EDN: missing closing ']'.
         let report = conn.transact(&mut sqlite, "[[:db/add \"t\" :db/ident :a/keyword]");
-        match report.expect_err("expected transact to fail for bad edn") {
-            MentatError::EdnParseError(_) => {}
+        match report.expect_err("expected transact to fail for bad edn").kind() {
+            &MentatErrorKind::EdnParseError(_) => { }
             x => panic!("expected EDN parse error, got {:?}", x),
         }
 
@@ -655,8 +662,8 @@ mod tests {
 
         // Bad transaction data: missing leading :db/add.
         let report = conn.transact(&mut sqlite, "[[\"t\" :db/ident :b/keyword]]");
-        match report.expect_err("expected transact error") {
-            MentatError::EdnParseError(_) => {}
+        match report.expect_err("expected transact error").kind() {
+            &MentatErrorKind::EdnParseError(_) => { }
             x => panic!("expected EDN parse error, got {:?}", x),
         }
 
@@ -668,12 +675,10 @@ mod tests {
 
         // Bad transaction based on state of store: conflicting upsert.
         let report = conn.transact(
-            &mut sqlite,
-            "[[:db/add \"u\" :db/ident :a/keyword]
-                                                  [:db/add \"u\" :db/ident :b/keyword]]",
-        );
-        match report.expect_err("expected transact error") {
-            MentatError::DbError(e) => match e.kind() {
+            &mut sqlite, "[[:db/add \"u\" :db/ident :a/keyword]
+                           [:db/add \"u\" :db/ident :b/keyword]]");
+        match report.expect_err("expected transact error").kind() {
+            &MentatErrorKind::DbError(ref e) => {
                 ::db_traits::errors::DbErrorKind::SchemaConstraintViolation(_) => {}
                 _ => panic!("expected SchemaConstraintViolation"),
             },
@@ -705,8 +710,8 @@ mod tests {
             CacheDirection::Forward,
             CacheAction::Register,
         );
-        match res.expect_err("expected cache to fail") {
-            MentatError::UnknownAttribute(msg) => assert_eq!(msg, ":foo/bat"),
+        match res.expect_err("expected cache to fail").kind() {
+            &MentatErrorKind::UnknownAttribute(ref msg) => assert_eq!(msg, ":foo/bat")
             x => panic!("expected UnknownAttribute error, got {:?}", x),
         }
     }

src/lib.rs

@@ -82,7 +82,7 @@ macro_rules! kw {
 }
 
 pub use public_traits::errors;
-pub use public_traits::errors::{MentatError, Result};
+pub use public_traits::errors::{MentatErrorKind, Result};
 
 pub use edn::{FromMicros, FromMillis, ParseError, ToMicros, ToMillis};
 pub use mentat_query_projector::BindingTuple;

src/query_builder.rs

@@ -17,7 +17,7 @@ use mentat_core::{DateTime, Keyword, Utc};
 
 use super::{HasSchema, QueryInputs, QueryOutput, Queryable, RelResult, Store, Variable};
 
-use public_traits::errors::{MentatError, Result};
+use public_traits::errors::{MentatErrorKind, Result};
 
 pub struct QueryBuilder<'a> {
     query: String,
@@ -49,12 +49,8 @@ impl<'a> QueryBuilder<'a> {
     }
 
     pub fn bind_ref_from_kw(&mut self, var: &str, value: Keyword) -> Result<&mut Self> {
-        let entid = self
-            .store
-            .conn()
-            .current_schema()
-            .get_entid(&value)
-            .ok_or(MentatError::UnknownAttribute(value.to_string()))?;
+        let entid = self.store.conn().current_schema().get_entid(&value).ok_or_else(||
+            MentatError::from(MentatErrorKind::UnknownAttribute(value.to_string())))?;
         self.values.insert(
             Variable::from_valid_name(var),
             TypedValue::Ref(entid.into()),

src/store.rs.rej

@@ -0,0 +1,29 @@
+--- src/store.rs
++++ src/store.rs
+@@ -85,7 +85,7 @@ impl Store {
+     pub fn open_empty(path: &str) -> Result<Store> {
+         if !path.is_empty() {
+             if Path::new(path).exists() {
+-                bail!(MentatError::PathAlreadyExists(path.to_string()));
++                bail!(MentatErrorKind::PathAlreadyExists(path.to_string()));
+             }
+         }
+ 
+@@ -125,7 +125,7 @@ impl Store {
+     pub fn open_empty_with_key(path: &str, encryption_key: &str) -> Result<Store> {
+         if !path.is_empty() {
+             if Path::new(path).exists() {
+-                bail!(MentatError::PathAlreadyExists(path.to_string()));
++                bail!(MentatErrorKind::PathAlreadyExists(path.to_string()));
+             }
+         }
+ 
+@@ -241,7 +241,7 @@ impl Pullable for Store {
+ #[cfg(feature = "syncable")]
+ impl Syncable for Store {
+     fn sync(&mut self, server_uri: &String, user_uuid: &String) -> Result<()> {
+-        let uuid = Uuid::parse_str(&user_uuid).map_err(|_| MentatError::BadUuid(user_uuid.clone()))?;
++        let uuid = Uuid::parse_str(&user_uuid).map_err(|_| MentatErrorKind::BadUuid(user_uuid.clone()))?;
+         Ok(Syncer::flow(&mut self.sqlite, server_uri, &uuid)?)
+     }
+ }

src/vocabulary.rs

@@ -101,7 +101,7 @@ use super::{
     CORE_SCHEMA_VERSION,
 };
 
-use super::errors::{MentatError, Result};
+use super::errors::{MentatErrorKind, Result};
 
 use mentat_transaction::{InProgress, Queryable};
 
@@ -325,17 +325,17 @@ where
 {
     fn core_type(&self, t: ValueType) -> Result<KnownEntid> {
         self.entid_for_type(t)
-            .ok_or_else(|| MentatError::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
+            .ok_or_else(|| MentatErrorKind::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
     }
 
     fn core_entid(&self, ident: &Keyword) -> Result<KnownEntid> {
         self.get_entid(ident)
-            .ok_or_else(|| MentatError::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
+            .ok_or_else(|| MentatErrorKind::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
     }
 
     fn core_attribute(&self, ident: &Keyword) -> Result<KnownEntid> {
         self.attribute_for_ident(ident)
-            .ok_or_else(|| MentatError::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
+            .ok_or_else(|| MentatErrorKind::MissingCoreVocabulary(DB_SCHEMA_VERSION.clone()).into())
             .map(|(_, e)| e)
     }
 }
@@ -548,7 +548,7 @@ pub trait VersionedStore: HasVocabularies + HasSchema {
                                 // We have two vocabularies with the same name, same version, and
                                 // different definitions for an attribute. That's a coding error.
                                 // We can't accept this vocabulary.
-                                bail!(MentatError::ConflictingAttributeDefinitions(
+                                bail!(MentatErrorKind::ConflictingAttributeDefinitions(
                                     definition.name.to_string(),
                                     definition.version,
                                     pair.0.to_string(),
@@ -604,7 +604,7 @@ pub trait VersionedStore: HasVocabularies + HasSchema {
     fn verify_core_schema(&self) -> Result<()> {
         if let Some(core) = self.read_vocabulary_named(&DB_SCHEMA_CORE)? {
             if core.version != CORE_SCHEMA_VERSION {
-                bail!(MentatError::UnexpectedCoreSchema(
+                bail!(MentatErrorKind::UnexpectedCoreSchema(
                     CORE_SCHEMA_VERSION,
                     Some(core.version)
                 ));
@@ -613,7 +613,7 @@ pub trait VersionedStore: HasVocabularies + HasSchema {
         // TODO: check things other than the version.
         } else {
             // This would be seriously messed up.
-            bail!(MentatError::UnexpectedCoreSchema(CORE_SCHEMA_VERSION, None));
+            bail!(MentatErrorKind::UnexpectedCoreSchema(CORE_SCHEMA_VERSION, None));
         }
         Ok(())
     }
@@ -694,7 +694,7 @@ impl<'a, 'c> VersionedStore for InProgress<'a, 'c> {
                 self.install_attributes_for(definition, attributes)
             }
             VocabularyCheck::PresentButTooNew { newer_version } => {
-                Err(MentatError::ExistingVocabularyTooNew(
+                Err(MentatErrorKind::ExistingVocabularyTooNew(
                     definition.name.to_string(),
                     newer_version.version,
                     definition.version,
@@ -722,7 +722,7 @@ impl<'a, 'c> VersionedStore for InProgress<'a, 'c> {
                     out.insert(definition.name.clone(), VocabularyOutcome::Existed);
                 }
                 VocabularyCheck::PresentButTooNew { newer_version } => {
-                    bail!(MentatError::ExistingVocabularyTooNew(
+                    bail!(MentatErrorKind::ExistingVocabularyTooNew(
                         definition.name.to_string(),
                         newer_version.version,
                         definition.version
@@ -914,7 +914,7 @@ where
                         attributes: attributes,
                     }))
                 }
-                Some(_) => bail!(MentatError::InvalidVocabularyVersion),
+                Some(_) => bail!(MentatErrorKind::InvalidVocabularyVersion),
             }
         } else {
             Ok(None)

tests/query.rs

@@ -37,7 +37,7 @@ use mentat::query::q_uncached;
 
 use mentat::conn::Conn;
 
-use public_traits::errors::MentatError;
+use public_traits::errors::MentatErrorKind;
 
 #[test]
 fn test_rel() {
@@ -243,10 +243,9 @@ fn test_unbound_inputs() {
         inputs,
     );
 
-    match results.expect_err("expected unbound variables") {
-        MentatError::UnboundVariables(vars) => {
-            assert_eq!(vars, vec!["?e".to_string()].into_iter().collect());
-        }
+    match results.expect_err("expected unbound variables").kind() {
+        &MentatErrorKind::UnboundVariables(ref vars) => {
+            assert_eq!(vars, &vec!["?e".to_string()].into_iter().collect());
         _ => panic!("Expected UnboundVariables variant."),
     }
 }
@@ -495,17 +494,15 @@ fn test_fulltext() {
                     [?a :foo/term ?term]
                     ]"#;
     let r = conn.q_once(&mut c, query, None);
-    match r.expect_err("expected query to fail") {
-        MentatError::AlgebrizerError(
-            query_algebrizer_traits::errors::AlgebrizerError::InvalidArgument(
-                PlainSymbol(s),
-                ty,
-                i,
-            ),
-        ) => {
-            assert_eq!(s, "fulltext");
-            assert_eq!(ty, "string");
-            assert_eq!(i, 2);
+    match r.expect_err("expected query to fail").kind() {
+        &MentatErrorKind::AlgebrizerError(ref e) => {
+            if let &mentat_query_algebrizer::AlgebrizerErrorKind::InvalidArgument(PlainSymbol(ref s), ref ty, ref i) = e.kind() {
+                assert_eq!(*s, "fulltext");
+                assert_eq!(*ty, "string");
+                assert_eq!(*i, 2);
+            } else {
+                panic!("Expected invalid argument");
+            }
         }
         _ => panic!("Expected query to fail."),
     }
@@ -516,17 +513,15 @@ fn test_fulltext() {
                     [?a :foo/term ?term]
                     [(fulltext $ :foo/fts ?a) [[?x ?val]]]]"#;
     let r = conn.q_once(&mut c, query, None);
-    match r.expect_err("expected query to fail") {
-        MentatError::AlgebrizerError(
-            query_algebrizer_traits::errors::AlgebrizerError::InvalidArgument(
-                PlainSymbol(s),
-                ty,
-                i,
-            ),
-        ) => {
-            assert_eq!(s, "fulltext");
-            assert_eq!(ty, "string");
-            assert_eq!(i, 2);
+    match r.expect_err("expected query to fail").kind() {
+        &MentatErrorKind::AlgebrizerError(ref e) => {
+            if let &mentat_query_algebrizer::AlgebrizerErrorKind::InvalidArgument(PlainSymbol(ref s), ref ty, ref i) = e.kind() {
+                assert_eq!(*s, "fulltext");
+                assert_eq!(*ty, "string");
+                assert_eq!(*i, 2);
+            } else {
+                panic!("expected AlgebrizerError::InvalidArgument");
+            }
         }
         _ => panic!("Expected query to fail."),
     }
@@ -732,14 +727,15 @@ fn test_aggregates_type_handling() {
     // No type limits => can't do it.
     let r = store.q_once(r#"[:find (sum ?v) . :where [_ _ ?v]]"#, None);
     let all_types = ValueTypeSet::any();
-    match r.expect_err("expected query to fail") {
-        MentatError::ProjectorError(
-            ::query_projector_traits::errors::ProjectorError::CannotApplyAggregateOperationToTypes(
-                SimpleAggregationOp::Sum,
-                types,
-            ),
-        ) => {
-            assert_eq!(types, all_types);
+    use mentat_query_projector::errors::ProjectorErrorKind;
+    match r.expect_err("expected query to fail").kind() {
+        &MentatErrorKind::ProjectorError(ref e) => {
+            if let &ProjectorErrorKind::CannotApplyAggregateOperationToTypes(
+                        SimpleAggregationOp::Sum, ref types) = e.kind() {
+                assert_eq!(types, &all_types);
+            } else {
+                panic!("Unexpected error type {:?}", e);
+            }
         }
         e => panic!("Unexpected error type {:?}", e),
     }
@@ -750,14 +746,14 @@ fn test_aggregates_type_handling() {
                              :where [_ _ ?v] [(type ?v :db.type/instant)]]"#,
         None,
     );
-    match r.expect_err("expected query to fail") {
-        MentatError::ProjectorError(
-            ::query_projector_traits::errors::ProjectorError::CannotApplyAggregateOperationToTypes(
-                SimpleAggregationOp::Sum,
-                types,
-            ),
-        ) => {
-            assert_eq!(types, ValueTypeSet::of_one(ValueType::Instant));
+    match r.expect_err("expected query to fail").kind() {
+        &MentatErrorKind::ProjectorError(ref e) => {
+            if let &ProjectorErrorKind::CannotApplyAggregateOperationToTypes(
+                        SimpleAggregationOp::Sum, ref types) = e.kind() {
+                assert_eq!(types, &ValueTypeSet::of_one(ValueType::Instant));
+            } else {
+                panic!("Unexpected error type {:?}", e);
+            }
         }
         e => panic!("Unexpected error type {:?}", e),
     }
@@ -1705,12 +1701,15 @@ fn test_aggregation_implicit_grouping() {
                                [?person :foo/name ?name]]"#,
         None,
     );
-    match res.expect_err("expected query to fail") {
-        MentatError::ProjectorError(
-            ::query_projector_traits::errors::ProjectorError::AmbiguousAggregates(mmc, cc),
-        ) => {
+    use mentat_query_projector::errors::ProjectorErrorKind;
+    match res.expect_err("expected query to fail").kind() {
+        &MentatErrorKind::ProjectorError(ref e) => {
+            if let &ProjectorErrorKind::AmbiguousAggregates(mmc, cc) = e.kind() {
                 assert_eq!(mmc, 2);
                 assert_eq!(cc, 1);
+            } else {
+                panic!("Unexpected error type {:?}.", e);
+            }
         }
         e => {
             panic!("Unexpected error type {:?}.", e);

tests/vocabulary.rs

@@ -40,7 +40,7 @@ use mentat::{
 
 use mentat::entity_builder::{BuildTerms, TermBuilder};
 
-use mentat::errors::MentatError;
+use mentat::errors::MentatErrorKind;
 
 lazy_static! {
     static ref FOO_NAME: Keyword = { kw!(:foo/name) };
@@ -327,12 +327,12 @@ fn test_add_vocab() {
             .ensure_vocabulary(&foo_v1_malformed)
             .expect_err("expected vocabulary to fail")
         {
-            MentatError::ConflictingAttributeDefinitions(vocab, version, attr, theirs, ours) => {
+            &MentatErrorKind::ConflictingAttributeDefinitions(vocab, version, attr, theirs, ours) => {
                 assert_eq!(vocab.as_str(), ":org.mozilla/foo");
                 assert_eq!(attr.as_str(), ":foo/baz");
-                assert_eq!(version, 1);
-                assert_eq!(&theirs, &baz);
-                assert_eq!(&ours, &malformed_baz);
+                assert_eq!(*version, 1);
+                assert_eq!(theirs, &baz);
+                assert_eq!(ours, &malformed_baz);
             }
             _ => panic!(),
         }

tools/cli/src/mentat_cli/repl.rs

@@ -376,7 +376,7 @@ impl Repl {
             let next = match encryption_key {
                 #[cfg(not(feature = "sqlcipher"))]
                 Some(_) => {
-                    return Err(::mentat::MentatError::RusqliteError(
+                    return Err(::mentat::MentatErrorKind::RusqliteError(
                         ".open_encrypted requires the sqlcipher Mentat feature".into(),
                         "".into(),
                     ))

transaction/src/query.rs

@@ -43,7 +43,7 @@ pub use mentat_query_projector::{
     RelResult,
 };
 
-use public_traits::errors::{MentatError, Result};
+use public_traits::errors::{MentatErrorKind, Result};
 
 pub type QueryExecutionResult = Result<QueryOutput>;
 pub type PreparedResult<'sqlite> = Result<PreparedQuery<'sqlite>>;
@@ -156,7 +156,7 @@ where
     // If they aren't, the user has made an error -- perhaps writing the wrong variable in `:in`, or
     // not binding in the `QueryInput`.
     if !unbound.is_empty() {
-        bail!(MentatError::UnboundVariables(
+        bail!(MentatErrorKind::UnboundVariables(
             unbound.into_iter().map(|v| v.to_string()).collect()
         ));
     }
@@ -198,7 +198,7 @@ fn fetch_values<'sqlite>(
 fn lookup_attribute(schema: &Schema, attribute: &Keyword) -> Result<KnownEntid> {
     schema
         .get_entid(attribute)
-        .ok_or_else(|| MentatError::UnknownAttribute(attribute.name().into()).into())
+        .ok_or_else(|| MentatErrorKind::UnknownAttribute(attribute.name().into()).into())
 }
 
 /// Return a single value for the provided entity and attribute.
@@ -415,7 +415,7 @@ where
     if !unbound.is_empty() {
         // TODO: Allow binding variables at execution time, not just
         // preparation time.
-        bail!(MentatError::UnboundVariables(
+        bail!(MentatErrorKind::UnboundVariables(
             unbound.into_iter().map(|v| v.to_string()).collect()
         ));
     }