Parse basic :find and :where clauses. (#211) r=nalexander

* Make Variable::from_symbol public.
* Implement basic parsing of queries.
* Use pinned dependencies the hard way to fix Travis.
* Bump ordered-float dependency to 0.4.0.
* Error coercions to use ?, and finishing the find interface.

db/Cargo.toml

@@ -7,7 +7,7 @@ error-chain = "0.8.0"
 lazy_static = "0.2.2"
 # TODO: don't depend on num and ordered-float; expose helpers in edn abstracting necessary constructors.
 num = "0.1.35"
-ordered-float = "0.3.0"
+ordered-float = "0.4.0"
 
 [dependencies.rusqlite]
 version = "0.9.3"

edn/Cargo.toml

@@ -11,7 +11,7 @@ readme = "./README.md"
 
 [dependencies]
 num = "0.1.35"
-ordered-float = "0.3.0"
+ordered-float = "0.4.0"
 
 [build-dependencies]
 peg = "0.4"

query-parser/Cargo.toml

@@ -4,6 +4,8 @@ version = "0.0.1"
 
 [dependencies]
 combine = "2.1.1"
+matches = "0.1"
+ordered-float = "0.4.0"
 
 [dependencies.edn]
   path = "../edn"

query-parser/src/error.rs

@@ -1,41 +0,0 @@
-// Copyright 2016 Mozilla
-//
-// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
-// this file except in compliance with the License. You may obtain a copy of the
-// License at http://www.apache.org/licenses/LICENSE-2.0
-// Unless required by applicable law or agreed to in writing, software distributed
-// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
-// CONDITIONS OF ANY KIND, either express or implied. See the License for the
-// specific language governing permissions and limitations under the License.
-
-extern crate combine;
-extern crate edn;
-extern crate mentat_query;
-
-use self::mentat_query::{FindSpec, FindQuery};
-
-#[derive(Clone,Debug,Eq,PartialEq)]
-pub struct NotAVariableError(pub edn::Value);
-
-#[derive(Clone,Debug,Eq,PartialEq)]
-pub enum FindParseError {
-  Err,
-}
-
-#[derive(Clone,Debug,Eq,PartialEq)]
-pub enum QueryParseError {
-    InvalidInput(edn::Value),
-    EdnParseError(edn::parse::ParseError),
-    MissingField(edn::Keyword),
-    FindParseError(FindParseError),
-}
-
-impl From<edn::parse::ParseError> for QueryParseError {
-    fn from(err: edn::parse::ParseError) -> QueryParseError {
-        QueryParseError::EdnParseError(err)
-    }
-}
-
-pub type FindParseResult = Result<FindSpec, FindParseError>;
-pub type QueryParseResult = Result<FindQuery, QueryParseError>;
-

query-parser/src/find.rs

@@ -38,10 +38,36 @@ extern crate mentat_query;
 
 use std::collections::BTreeMap;
 
-use self::mentat_query::{FindQuery, SrcVar};
+use self::mentat_query::{
+    FindQuery,
+    FromValue,
+    SrcVar,
+    Variable,
+};
 
-use super::error::{QueryParseError, QueryParseResult};
+use super::parse::{
-use super::util::{values_to_variables, vec_to_keyword_map};
+    NotAVariableError,
+    QueryParseError,
+    QueryParseResult,
+    clause_seq_to_patterns,
+};
+
+use super::util::vec_to_keyword_map;
+
+/// If the provided slice of EDN values are all variables as
+/// defined by `value_to_variable`, return a `Vec` of `Variable`s.
+/// Otherwise, return the unrecognized Value in a `NotAVariableError`.
+fn values_to_variables(vals: &[edn::Value]) -> Result<Vec<Variable>, NotAVariableError> {
+    let mut out: Vec<Variable> = Vec::with_capacity(vals.len());
+    for v in vals {
+        if let Some(var) = Variable::from_value(v) {
+            out.push(var);
+            continue;
+        }
+        return Err(NotAVariableError(v.clone()));
+    }
+    return Ok(out);
+}
 
 #[allow(unused_variables)]
 fn parse_find_parts(find: &[edn::Value],
@@ -63,19 +89,27 @@ fn parse_find_parts(find: &[edn::Value],
     let source = SrcVar::DefaultSrc;
 
     // :with is an array of variables. This is simple, so we don't use a parser.
-    let with_vars = with.map(values_to_variables);
+    let with_vars = if let Some(vals) = with {
+        values_to_variables(vals)?
+    } else {
+        vec![]
+    };
+
     // :wheres is a whole datastructure.
+    let where_clauses = clause_seq_to_patterns(wheres)?;
 
     super::parse::find_seq_to_find_spec(find)
         .map(|spec| {
             FindQuery {
                 find_spec: spec,
                 default_source: source,
+                with: with_vars,
+                in_vars: vec!(),       // TODO
+                in_sources: vec!(),    // TODO
+                where_clauses: where_clauses,
             }
         })
         .map_err(QueryParseError::FindParseError)
-
-
 }
 
 fn parse_find_map(map: BTreeMap<edn::Keyword, Vec<edn::Value>>) -> QueryParseResult {
@@ -136,3 +170,64 @@ pub fn parse_find(expr: edn::Value) -> QueryParseResult {
     }
     return Err(QueryParseError::InvalidInput(expr));
 }
+
+#[cfg(test)]
+mod test_parse {
+    extern crate edn;
+
+    use self::edn::{NamespacedKeyword, PlainSymbol};
+    use self::edn::types::{to_keyword, to_symbol};
+    use super::mentat_query::{
+        Element,
+        FindSpec,
+        Pattern,
+        PatternNonValuePlace,
+        PatternValuePlace,
+        SrcVar,
+        Variable,
+        WhereClause,
+    };
+    use super::*;
+
+    // TODO: when #224 lands, fix to_keyword to be variadic.
+    #[test]
+    fn test_parse_find() {
+        let truncated_input = edn::Value::Vector(vec![to_keyword(None, "find")]);
+        assert!(parse_find(truncated_input).is_err());
+
+        let input = edn::Value::Vector(vec![
+                                       to_keyword(None, "find"),
+                                       to_symbol(None, "?x"),
+                                       to_symbol(None, "?y"),
+                                       to_keyword(None, "where"),
+                                       edn::Value::Vector(vec![
+                                                          to_symbol(None, "?x"),
+                                                          to_keyword("foo", "bar"),
+                                                          to_symbol(None, "?y"),
+                                       ]),
+        ]);
+
+        let parsed = parse_find(input).unwrap();
+        if let FindSpec::FindRel(elems) = parsed.find_spec {
+            assert_eq!(2, elems.len());
+            assert_eq!(vec![
+                       Element::Variable(Variable(edn::PlainSymbol::new("?x"))),
+                       Element::Variable(Variable(edn::PlainSymbol::new("?y"))),
+            ], elems);
+        } else {
+            panic!("Expected FindRel.");
+        }
+
+        assert_eq!(SrcVar::DefaultSrc, parsed.default_source);
+        assert_eq!(parsed.where_clauses,
+                   vec![
+                   WhereClause::Pattern(Pattern {
+                       source: None,
+                       entity: PatternNonValuePlace::Variable(Variable(PlainSymbol::new("?x"))),
+                       attribute: PatternNonValuePlace::Ident(NamespacedKeyword::new("foo", "bar")),
+                       value: PatternValuePlace::Variable(Variable(PlainSymbol::new("?y"))),
+                       tx: PatternNonValuePlace::Placeholder,
+                   })]);
+
+    }
+}

query-parser/src/lib.rs

@@ -8,10 +8,14 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
+#[macro_use]
+extern crate matches;
+
 #[macro_use]
 extern crate mentat_parser_utils;
 
-mod error;
+#[macro_use]
+mod parser_util;
 mod util;
 mod parse;
 pub mod find;

query-parser/src/parse.rs

@@ -10,156 +10,207 @@
 
 extern crate combine;
 extern crate edn;
+extern crate mentat_parser_utils;
 extern crate mentat_query;
 
-use self::combine::{eof, many1, parser, satisfy_map, Parser, ParseResult, Stream};
+use self::mentat_parser_utils::ResultParser;
-use self::combine::combinator::{Expected, FnParser, choice, try};
+use self::combine::{eof, many1, optional, parser, satisfy_map, Parser, ParseResult, Stream};
-use self::edn::Value::PlainSymbol;
+use self::combine::combinator::{choice, try};
-use self::mentat_query::{Element, FromValue, FindSpec, Variable};
+use self::mentat_query::{
+    Element,
+    FindQuery,
+    FindSpec,
+    FromValue,
+    Pattern,
+    PatternNonValuePlace,
+    PatternValuePlace,
+    SrcVar,
+    Variable,
+    WhereClause,
+};
 
-use super::error::{FindParseError, FindParseResult};
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct NotAVariableError(pub edn::Value);
 
-pub struct FindSp<I>(::std::marker::PhantomData<fn(I) -> I>);
+#[allow(dead_code)]
-
+#[derive(Clone, Debug, Eq, PartialEq)]
-type FindSpParser<O, I> = Expected<FnParser<I, fn(I) -> ParseResult<O, I>>>;
+pub enum FindParseError {
-
+    Err,
-fn fn_parser<O, I>(f: fn(I) -> ParseResult<O, I>, err: &'static str) -> FindSpParser<O, I>
-    where I: Stream<Item = edn::Value>
-{
-    parser(f).expected(err)
 }
 
-/// `satisfy_unwrap!` makes it a little easier to implement a `satisfy_map`
+#[allow(dead_code)]
-/// body that matches a particular `Value` enum case, otherwise returning `None`.
+#[derive(Clone, Debug, Eq, PartialEq)]
-macro_rules! satisfy_unwrap {
+pub enum WhereParseError {
-    ( $cas: path, $var: ident, $body: block ) => {
+    Err,
-        satisfy_map(|x: edn::Value| if let $cas($var) = x $body else { None })
+}
+
+#[derive(Clone,Debug,Eq,PartialEq)]
+pub enum QueryParseError {
+    InvalidInput(edn::Value),
+    EdnParseError(edn::parse::ParseError),
+    MissingField(edn::Keyword),
+    FindParseError(FindParseError),
+    WhereParseError(WhereParseError),
+    WithParseError(NotAVariableError),
+}
+
+impl From<edn::parse::ParseError> for QueryParseError {
+    fn from(err: edn::parse::ParseError) -> QueryParseError {
+        QueryParseError::EdnParseError(err)
     }
 }
 
-impl<I> FindSp<I>
+impl From<WhereParseError> for QueryParseError {
+    fn from(err: WhereParseError) -> QueryParseError {
+        QueryParseError::WhereParseError(err)
+    }
+}
+
+impl From<NotAVariableError> for QueryParseError {
+    fn from(err: NotAVariableError) -> QueryParseError {
+        QueryParseError::WithParseError(err)
+    }
+}
+
+pub type WhereParseResult = Result<Vec<WhereClause>, WhereParseError>;
+pub type FindParseResult = Result<FindSpec, FindParseError>;
+pub type QueryParseResult = Result<FindQuery, QueryParseError>;
+
+
+pub struct Query<I>(::std::marker::PhantomData<fn(I) -> I>);
+
+impl<I> Query<I>
     where I: Stream<Item = edn::Value>
 {
-    fn variable() -> FindSpParser<Variable, I> {
-        fn_parser(FindSp::<I>::variable_, "variable")
-    }
-
-    fn variable_(input: I) -> ParseResult<Variable, I> {
-        satisfy_map(|x: edn::Value| Variable::from_value(&x)).parse_stream(input)
-    }
-
-    fn period() -> FindSpParser<(), I> {
-        fn_parser(FindSp::<I>::period_, "period")
-    }
-
-    fn period_(input: I) -> ParseResult<(), I> {
-        satisfy_map(|x: edn::Value| {
-                if let PlainSymbol(ref s) = x {
-                    if s.0.as_str() == "." {
-                        return Some(());
-                    }
-                }
-                return None;
-            })
-            .parse_stream(input)
-    }
-
-    fn ellipsis() -> FindSpParser<(), I> {
-        fn_parser(FindSp::<I>::ellipsis_, "ellipsis")
-    }
-
-    fn ellipsis_(input: I) -> ParseResult<(), I> {
-        satisfy_map(|x: edn::Value| {
-                if let PlainSymbol(ref s) = x {
-                    if s.0.as_str() == "..." {
-                        return Some(());
-                    }
-                }
-                return None;
-            })
-            .parse_stream(input)
-    }
-
-    fn find_scalar() -> FindSpParser<FindSpec, I> {
-        fn_parser(FindSp::<I>::find_scalar_, "find_scalar")
-    }
-
-    fn find_scalar_(input: I) -> ParseResult<FindSpec, I> {
-        (FindSp::variable(), FindSp::period(), eof())
-            .map(|(var, _, _)| FindSpec::FindScalar(Element::Variable(var)))
-            .parse_stream(input)
-    }
-
-    fn find_coll() -> FindSpParser<FindSpec, I> {
-        fn_parser(FindSp::<I>::find_coll_, "find_coll")
-    }
-
-    fn find_coll_(input: I) -> ParseResult<FindSpec, I> {
-        satisfy_unwrap!(edn::Value::Vector, y, {
-                let mut p = (FindSp::variable(), FindSp::ellipsis(), eof())
-                    .map(|(var, _, _)| FindSpec::FindColl(Element::Variable(var)));
-                let r: ParseResult<FindSpec, _> = p.parse_lazy(&y[..]).into();
-                FindSp::to_parsed_value(r)
-            })
-            .parse_stream(input)
-    }
-
-    fn elements() -> FindSpParser<Vec<Element>, I> {
-        fn_parser(FindSp::<I>::elements_, "elements")
-    }
-
-    fn elements_(input: I) -> ParseResult<Vec<Element>, I> {
-        (many1::<Vec<Variable>, _>(FindSp::variable()), eof())
-            .map(|(vars, _)| {
-                vars.into_iter()
-                    .map(Element::Variable)
-                    .collect()
-            })
-            .parse_stream(input)
-    }
-
-    fn find_rel() -> FindSpParser<FindSpec, I> {
-        fn_parser(FindSp::<I>::find_rel_, "find_rel")
-    }
-
-    fn find_rel_(input: I) -> ParseResult<FindSpec, I> {
-        FindSp::elements().map(FindSpec::FindRel).parse_stream(input)
-    }
-
-    fn find_tuple() -> FindSpParser<FindSpec, I> {
-        fn_parser(FindSp::<I>::find_tuple_, "find_tuple")
-    }
-
-    fn find_tuple_(input: I) -> ParseResult<FindSpec, I> {
-        satisfy_unwrap!(edn::Value::Vector, y, {
-                let r: ParseResult<FindSpec, _> =
-                    FindSp::elements().map(FindSpec::FindTuple).parse_lazy(&y[..]).into();
-                FindSp::to_parsed_value(r)
-            })
-            .parse_stream(input)
-    }
-
-    fn find() -> FindSpParser<FindSpec, I> {
-        fn_parser(FindSp::<I>::find_, "find")
-    }
-
-    fn find_(input: I) -> ParseResult<FindSpec, I> {
-        // Any one of the four specs might apply, so we combine them with `choice`.
-        // Our parsers consume input, so we need to wrap them in `try` so that they
-        // operate independently.
-        choice::<[&mut Parser<Input = I, Output = FindSpec>; 4],
-                 _>([&mut try(FindSp::find_scalar()),
-                     &mut try(FindSp::find_coll()),
-                     &mut try(FindSp::find_tuple()),
-                     &mut try(FindSp::find_rel())])
-            .parse_stream(input)
-    }
-
     fn to_parsed_value<T>(r: ParseResult<T, I>) -> Option<T> {
         r.ok().map(|x| x.0)
     }
 }
 
+def_value_satisfy_parser_fn!(Query, variable, Variable, Variable::from_value);
+def_value_satisfy_parser_fn!(Query, source_var, SrcVar, SrcVar::from_value);
+
+pub struct Where<I>(::std::marker::PhantomData<fn(I) -> I>);
+
+def_value_satisfy_parser_fn!(Where, pattern_value_place, PatternValuePlace, PatternValuePlace::from_value);
+def_value_satisfy_parser_fn!(Where, pattern_non_value_place, PatternNonValuePlace, PatternNonValuePlace::from_value);
+
+def_value_parser_fn!(Where, pattern, Pattern, input, {
+    satisfy_map(|x: edn::Value| {
+        if let edn::Value::Vector(y) = x {
+            // While *technically* Datomic allows you to have a query like:
+            // [:find … :where [[?x]]]
+            // We don't -- we require at list e, a.
+            let mut p =
+                (optional(Query::source_var()),                 // src
+                 Where::pattern_non_value_place(),              // e
+                 Where::pattern_non_value_place(),              // a
+                 optional(Where::pattern_value_place()),        // v
+                 optional(Where::pattern_non_value_place()),    // tx
+                 eof())
+                .map(|(src, e, a, v, tx, _)| {
+                    let v = v.unwrap_or(PatternValuePlace::Placeholder);
+                    let tx = tx.unwrap_or(PatternNonValuePlace::Placeholder);
+
+                    // Pattern::new takes care of reversal of reversed
+                    // attributes: [?x :foo/_bar ?y] turns into
+                    // [?y :foo/bar ?x].
+                    Pattern::new(src, e, a, v, tx)
+                });
+
+            // This is a bit messy: the inner conversion to a Pattern can
+            // fail if the input is something like
+            //
+            // ```edn
+            // [?x :foo/_reversed 23.4]
+            // ```
+            //
+            // because
+            //
+            // ```edn
+            // [23.4 :foo/reversed ?x]
+            // ```
+            //
+            // is nonsense. That leaves us with nested optionals; we unwrap them here.
+            let r: ParseResult<Option<Pattern>, _> = p.parse_lazy(&y[..]).into();
+            let v: Option<Option<Pattern>> = r.ok().map(|x| x.0);
+            v.unwrap_or(None)
+        } else {
+            None
+        }
+    }).parse_stream(input)
+});
+
+def_value_parser_fn!(Where, clauses, Vec<WhereClause>, input, {
+    // Right now we only support patterns. See #239 for more.
+    (many1::<Vec<Pattern>, _>(Where::pattern()), eof())
+        .map(|(patterns, _)| {
+            patterns.into_iter().map(WhereClause::Pattern).collect()
+        })
+    .parse_stream(input)
+});
+
+pub struct Find<I>(::std::marker::PhantomData<fn(I) -> I>);
+
+def_value_parser_fn!(Find, period, (), input, {
+    matches_plain_symbol!(".", input)
+});
+
+def_value_parser_fn!(Find, ellipsis, (), input, {
+    matches_plain_symbol!("...", input)
+});
+
+def_value_parser_fn!(Find, find_scalar, FindSpec, input, {
+    (Query::variable(), Find::period(), eof())
+        .map(|(var, _, _)| FindSpec::FindScalar(Element::Variable(var)))
+        .parse_stream(input)
+});
+
+def_value_parser_fn!(Find, find_coll, FindSpec, input, {
+    satisfy_unwrap!(edn::Value::Vector, y, {
+            let mut p = (Query::variable(), Find::ellipsis(), eof())
+                .map(|(var, _, _)| FindSpec::FindColl(Element::Variable(var)));
+            let r: ParseResult<FindSpec, _> = p.parse_lazy(&y[..]).into();
+            Query::to_parsed_value(r)
+        })
+        .parse_stream(input)
+});
+
+def_value_parser_fn!(Find, elements, Vec<Element>, input, {
+    (many1::<Vec<Variable>, _>(Query::variable()), eof())
+        .map(|(vars, _)| {
+            vars.into_iter()
+                .map(Element::Variable)
+                .collect()
+        })
+        .parse_stream(input)
+});
+
+def_value_parser_fn!(Find, find_rel, FindSpec, input, {
+    Find::elements().map(FindSpec::FindRel).parse_stream(input)
+});
+
+def_value_parser_fn!(Find, find_tuple, FindSpec, input, {
+    satisfy_unwrap!(edn::Value::Vector, y, {
+        let r: ParseResult<FindSpec, _> =
+            Find::elements().map(FindSpec::FindTuple).parse_lazy(&y[..]).into();
+        Query::to_parsed_value(r)
+    })
+    .parse_stream(input)
+});
+
+def_value_parser_fn!(Find, find, FindSpec, input, {
+    // Any one of the four specs might apply, so we combine them with `choice`.
+    // Our parsers consume input, so we need to wrap them in `try` so that they
+    // operate independently.
+    choice::<[&mut Parser<Input = I, Output = FindSpec>; 4], _>
+        ([&mut try(Find::find_scalar()),
+          &mut try(Find::find_coll()),
+          &mut try(Find::find_tuple()),
+          &mut try(Find::find_rel())])
+        .parse_stream(input)
+});
+
 // Parse a sequence of values into one of four find specs.
 //
 // `:find` must be an array of plain var symbols (?foo), pull expressions, and aggregates.
@@ -172,29 +223,131 @@ impl<I> FindSp<I>
 //     `?x .      `     = FindScalar
 //     `[?x ?y ?z]`     = FindTuple
 //
+#[allow(dead_code)]
 pub fn find_seq_to_find_spec(find: &[edn::Value]) -> FindParseResult {
-    FindSp::find()
+    Find::find()
         .parse(find)
         .map(|x| x.0)
         .map_err(|_| FindParseError::Err)
 }
 
+#[allow(dead_code)]
+pub fn clause_seq_to_patterns(clauses: &[edn::Value]) -> WhereParseResult {
+    Where::clauses()
+        .parse(clauses)
+        .map(|x| x.0)
+        .map_err(|_| WhereParseError::Err)
+}
+
 #[cfg(test)]
 mod test {
     extern crate combine;
     extern crate edn;
     extern crate mentat_query;
+    extern crate ordered_float;
 
     use self::combine::Parser;
-    use self::mentat_query::{Element, FindSpec, Variable};
+    use self::ordered_float::OrderedFloat;
+    use self::mentat_query::{
+        Element,
+        FindSpec,
+        NonIntegerConstant,
+        Pattern,
+        PatternNonValuePlace,
+        PatternValuePlace,
+        SrcVar,
+        Variable,
+    };
 
     use super::*;
 
+    #[test]
+    fn test_pattern_mixed() {
+        let e = edn::PlainSymbol::new("_");
+        let a = edn::NamespacedKeyword::new("foo", "bar");
+        let v = OrderedFloat(99.9);
+        let tx = edn::PlainSymbol::new("?tx");
+        let input = [edn::Value::Vector(
+            vec!(edn::Value::PlainSymbol(e.clone()),
+                 edn::Value::NamespacedKeyword(a.clone()),
+                 edn::Value::Float(v.clone()),
+                 edn::Value::PlainSymbol(tx.clone())))];
+        assert_parses_to!(Where::pattern, input, Pattern {
+            source: None,
+            entity: PatternNonValuePlace::Placeholder,
+            attribute: PatternNonValuePlace::Ident(a),
+            value: PatternValuePlace::Constant(NonIntegerConstant::Float(v)),
+            tx: PatternNonValuePlace::Variable(Variable(tx)),
+        });
+    }
+
+    #[test]
+    fn test_pattern_vars() {
+        let s = edn::PlainSymbol::new("$x");
+        let e = edn::PlainSymbol::new("?e");
+        let a = edn::PlainSymbol::new("?a");
+        let v = edn::PlainSymbol::new("?v");
+        let tx = edn::PlainSymbol::new("?tx");
+        let input = [edn::Value::Vector(
+            vec!(edn::Value::PlainSymbol(s.clone()),
+                 edn::Value::PlainSymbol(e.clone()),
+                 edn::Value::PlainSymbol(a.clone()),
+                 edn::Value::PlainSymbol(v.clone()),
+                 edn::Value::PlainSymbol(tx.clone())))];
+        assert_parses_to!(Where::pattern, input, Pattern {
+            source: Some(SrcVar::NamedSrc("x".to_string())),
+            entity: PatternNonValuePlace::Variable(Variable(e)),
+            attribute: PatternNonValuePlace::Variable(Variable(a)),
+            value: PatternValuePlace::Variable(Variable(v)),
+            tx: PatternNonValuePlace::Variable(Variable(tx)),
+        });
+    }
+
+    #[test]
+    fn test_pattern_reversed_invalid() {
+        let e = edn::PlainSymbol::new("_");
+        let a = edn::NamespacedKeyword::new("foo", "_bar");
+        let v = OrderedFloat(99.9);
+        let tx = edn::PlainSymbol::new("?tx");
+        let input = [edn::Value::Vector(
+            vec!(edn::Value::PlainSymbol(e.clone()),
+                 edn::Value::NamespacedKeyword(a.clone()),
+                 edn::Value::Float(v.clone()),
+                 edn::Value::PlainSymbol(tx.clone())))];
+
+        let mut par = Where::pattern();
+        let result = par.parse(&input[..]);
+        assert!(matches!(result, Err(_)), "Expected a parse error.");
+    }
+
+    #[test]
+    fn test_pattern_reversed() {
+        let e = edn::PlainSymbol::new("_");
+        let a = edn::NamespacedKeyword::new("foo", "_bar");
+        let v = edn::PlainSymbol::new("?v");
+        let tx = edn::PlainSymbol::new("?tx");
+        let input = [edn::Value::Vector(
+            vec!(edn::Value::PlainSymbol(e.clone()),
+                 edn::Value::NamespacedKeyword(a.clone()),
+                 edn::Value::PlainSymbol(v.clone()),
+                 edn::Value::PlainSymbol(tx.clone())))];
+
+        // Note that the attribute is no longer reversed, and the entity and value have
+        // switched places.
+        assert_parses_to!(Where::pattern, input, Pattern {
+            source: None,
+            entity: PatternNonValuePlace::Variable(Variable(v)),
+            attribute: PatternNonValuePlace::Ident(edn::NamespacedKeyword::new("foo", "bar")),
+            value: PatternValuePlace::Placeholder,
+            tx: PatternNonValuePlace::Variable(Variable(tx)),
+        });
+    }
+
     #[test]
     fn test_find_sp_variable() {
         let sym = edn::PlainSymbol::new("?x");
         let input = [edn::Value::PlainSymbol(sym.clone())];
-        assert_parses_to!(FindSp::variable, input, Variable(sym));
+        assert_parses_to!(Query::variable, input, Variable(sym));
     }
 
     #[test]
@@ -202,7 +355,7 @@ mod test {
         let sym = edn::PlainSymbol::new("?x");
         let period = edn::PlainSymbol::new(".");
         let input = [edn::Value::PlainSymbol(sym.clone()), edn::Value::PlainSymbol(period.clone())];
-        assert_parses_to!(FindSp::find_scalar,
+        assert_parses_to!(Find::find_scalar,
                           input,
                           FindSpec::FindScalar(Element::Variable(Variable(sym))));
     }
@@ -213,7 +366,7 @@ mod test {
         let period = edn::PlainSymbol::new("...");
         let input = [edn::Value::Vector(vec![edn::Value::PlainSymbol(sym.clone()),
                                              edn::Value::PlainSymbol(period.clone())])];
-        assert_parses_to!(FindSp::find_coll,
+        assert_parses_to!(Find::find_coll,
                           input,
                           FindSpec::FindColl(Element::Variable(Variable(sym))));
     }
@@ -223,7 +376,7 @@ mod test {
         let vx = edn::PlainSymbol::new("?x");
         let vy = edn::PlainSymbol::new("?y");
         let input = [edn::Value::PlainSymbol(vx.clone()), edn::Value::PlainSymbol(vy.clone())];
-        assert_parses_to!(FindSp::find_rel,
+        assert_parses_to!(Find::find_rel,
                           input,
                           FindSpec::FindRel(vec![Element::Variable(Variable(vx)),
                                                  Element::Variable(Variable(vy))]));
@@ -235,7 +388,7 @@ mod test {
         let vy = edn::PlainSymbol::new("?y");
         let input = [edn::Value::Vector(vec![edn::Value::PlainSymbol(vx.clone()),
                                              edn::Value::PlainSymbol(vy.clone())])];
-        assert_parses_to!(FindSp::find_tuple,
+        assert_parses_to!(Find::find_tuple,
                           input,
                           FindSpec::FindTuple(vec![Element::Variable(Variable(vx)),
                                                    Element::Variable(Variable(vy))]));

query-parser/src/parser_util.rs

@@ -10,6 +10,8 @@
 
 extern crate combine;
 extern crate edn;
+
+extern crate mentat_parser_utils;
 extern crate mentat_query;
 
 /// Generate a `satisfy_map` expression that matches a `PlainSymbol`

query-parser/src/util.rs

@@ -9,33 +9,9 @@
 // specific language governing permissions and limitations under the License.
 
 extern crate edn;
-extern crate mentat_query;
 
 use std::collections::BTreeMap;
 
-use self::mentat_query::{FromValue, Variable};
-use super::error::NotAVariableError;
-
-/// If the provided slice of EDN values are all variables as
-/// defined by `value_to_variable`, return a Vec of Variables.
-/// Otherwise, return the unrecognized Value.
-pub fn values_to_variables(vals: &[edn::Value]) -> Result<Vec<Variable>, NotAVariableError> {
-    let mut out: Vec<Variable> = Vec::with_capacity(vals.len());
-    for v in vals {
-        if let Some(var) = Variable::from_value(v) {
-            out.push(var);
-            continue;
-        }
-        return Err(NotAVariableError(v.clone()));
-    }
-    return Ok(out);
-}
-
-#[test]
-fn test_values_to_variables() {
-    // TODO
-}
-
 /// Take a slice of EDN values, as would be extracted from an
 /// `edn::Value::Vector`, and turn it into a map.
 ///

query/Cargo.toml

@@ -3,8 +3,8 @@ name = "mentat_query"
 version = "0.0.1"
 
 [dependencies]
-[dependencies.num]             # For EDN value usage.
+num = "0.1.35"
-[dependencies.ordered-float]
+ordered-float = "0.4.0"
 
 [dependencies.edn]
   path = "../edn"

query/src/lib.rs

@@ -60,7 +60,7 @@ impl FromValue<Variable> for Variable {
 }
 
 impl Variable {
-    fn from_symbol(sym: &PlainSymbol) -> Option<Variable> {
+    pub fn from_symbol(sym: &PlainSymbol) -> Option<Variable> {
         if sym.is_var_symbol() {
             Some(Variable(sym.clone()))
         } else {
@@ -96,7 +96,7 @@ impl SrcVar {
 }
 
 /// These are the scalar values representable in EDN.
-#[derive(Clone,Debug,Eq,PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub enum NonIntegerConstant {
     Boolean(bool),
     BigInteger(BigInt),
@@ -118,24 +118,128 @@ pub enum FnArg {
 /// This encoding allows us to represent integers that aren't
 /// entity IDs. That'll get filtered out in the context of the
 /// database.
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub enum PatternNonValuePlace {
     Placeholder,
     Variable(Variable),
-    Entid(u64),                       // Note unsigned. See #190.
+    Entid(i64),                       // Will always be +ve. See #190.
     Ident(NamespacedKeyword),
 }
 
+impl PatternNonValuePlace {
+    // I think we'll want move variants, so let's leave these here for now.
+    #[allow(dead_code)]
+    fn into_pattern_value_place(self) -> PatternValuePlace {
+        match self {
+            PatternNonValuePlace::Placeholder => PatternValuePlace::Placeholder,
+            PatternNonValuePlace::Variable(x) => PatternValuePlace::Variable(x),
+            PatternNonValuePlace::Entid(x)    => PatternValuePlace::EntidOrInteger(x),
+            PatternNonValuePlace::Ident(x)    => PatternValuePlace::IdentOrKeyword(x),
+        }
+    }
+
+    fn to_pattern_value_place(&self) -> PatternValuePlace {
+        match *self {
+            PatternNonValuePlace::Placeholder     => PatternValuePlace::Placeholder,
+            PatternNonValuePlace::Variable(ref x) => PatternValuePlace::Variable(x.clone()),
+            PatternNonValuePlace::Entid(x)        => PatternValuePlace::EntidOrInteger(x),
+            PatternNonValuePlace::Ident(ref x)    => PatternValuePlace::IdentOrKeyword(x.clone()),
+        }
+    }
+}
+
+impl FromValue<PatternNonValuePlace> for PatternNonValuePlace {
+    fn from_value(v: &edn::Value) -> Option<PatternNonValuePlace> {
+        match v {
+            &edn::Value::Integer(x) => if x >= 0 {
+                Some(PatternNonValuePlace::Entid(x))
+            } else {
+                None
+            },
+            &edn::Value::PlainSymbol(ref x) => if x.0.as_str() == "_" {
+                Some(PatternNonValuePlace::Placeholder)
+            } else {
+                if let Some(v) = Variable::from_symbol(x) {
+                    Some(PatternNonValuePlace::Variable(v))
+                } else {
+                    None
+                }
+            },
+            &edn::Value::NamespacedKeyword(ref x) =>
+                Some(PatternNonValuePlace::Ident(x.clone())),
+            _ => None,
+        }
+    }
+}
+
 /// The `v` part of a pattern can be much broader: it can represent
 /// integers that aren't entity IDs (particularly negative integers),
 /// strings, and all the rest. We group those under `Constant`.
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub enum PatternValuePlace {
     Placeholder,
     Variable(Variable),
     EntidOrInteger(i64),
-    Ident(NamespacedKeyword),
+    IdentOrKeyword(NamespacedKeyword),
     Constant(NonIntegerConstant),
 }
 
+impl FromValue<PatternValuePlace> for PatternValuePlace {
+    fn from_value(v: &edn::Value) -> Option<PatternValuePlace> {
+        match v {
+            &edn::Value::Integer(x) =>
+                Some(PatternValuePlace::EntidOrInteger(x)),
+            &edn::Value::PlainSymbol(ref x) if x.0.as_str() == "_" =>
+                Some(PatternValuePlace::Placeholder),
+            &edn::Value::PlainSymbol(ref x) if x.is_var_symbol() =>
+                Some(PatternValuePlace::Variable(Variable(x.clone()))),
+            &edn::Value::NamespacedKeyword(ref x) =>
+                Some(PatternValuePlace::IdentOrKeyword(x.clone())),
+            &edn::Value::Boolean(x) =>
+                Some(PatternValuePlace::Constant(NonIntegerConstant::Boolean(x))),
+            &edn::Value::Float(x) =>
+                Some(PatternValuePlace::Constant(NonIntegerConstant::Float(x))),
+            &edn::Value::BigInteger(ref x) =>
+                Some(PatternValuePlace::Constant(NonIntegerConstant::BigInteger(x.clone()))),
+            &edn::Value::Text(ref x) =>
+                Some(PatternValuePlace::Constant(NonIntegerConstant::Text(x.clone()))),
+            _ => None,
+        }
+    }
+}
+
+impl PatternValuePlace {
+    // I think we'll want move variants, so let's leave these here for now.
+    #[allow(dead_code)]
+    fn into_pattern_non_value_place(self) -> Option<PatternNonValuePlace> {
+        match self {
+            PatternValuePlace::Placeholder       => Some(PatternNonValuePlace::Placeholder),
+            PatternValuePlace::Variable(x)       => Some(PatternNonValuePlace::Variable(x)),
+            PatternValuePlace::EntidOrInteger(x) => if x >= 0 {
+                Some(PatternNonValuePlace::Entid(x))
+            } else {
+                None
+            },
+            PatternValuePlace::IdentOrKeyword(x) => Some(PatternNonValuePlace::Ident(x)),
+            PatternValuePlace::Constant(_)       => None,
+        }
+    }
+
+    fn to_pattern_non_value_place(&self) -> Option<PatternNonValuePlace> {
+        match *self {
+            PatternValuePlace::Placeholder           => Some(PatternNonValuePlace::Placeholder),
+            PatternValuePlace::Variable(ref x)       => Some(PatternNonValuePlace::Variable(x.clone())),
+            PatternValuePlace::EntidOrInteger(x)     => if x >= 0 {
+                Some(PatternNonValuePlace::Entid(x))
+            } else {
+                None
+            },
+            PatternValuePlace::IdentOrKeyword(ref x) => Some(PatternNonValuePlace::Ident(x.clone())),
+            PatternValuePlace::Constant(_)           => None,
+        }
+    }
+}
+
 /*
 pub enum PullPattern {
     Constant(Constant),
@@ -212,13 +316,6 @@ pub enum FindSpec {
     FindScalar(Element),
 }
 
-#[derive(Clone,Debug,Eq,PartialEq)]
-#[allow(dead_code)]
-pub struct FindQuery {
-    pub find_spec: FindSpec,
-    pub default_source: SrcVar,
-}
-
 /// Returns true if the provided `FindSpec` returns at most one result.
 pub fn is_unit_limited(spec: &FindSpec) -> bool {
     match spec {
@@ -255,18 +352,55 @@ pub fn requires_distinct(spec: &FindSpec) -> bool {
 // A pattern with a reversed attribute — :foo/_bar — is reversed
 // at the point of parsing. These `Pattern` instances only represent
 // one direction.
-#[allow(dead_code)]
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub struct Pattern {
-    source: Option<SrcVar>,
+    pub source: Option<SrcVar>,
-    entity: PatternNonValuePlace,
+    pub entity: PatternNonValuePlace,
-    attribute: PatternNonValuePlace,
+    pub attribute: PatternNonValuePlace,
-    value: PatternValuePlace,
+    pub value: PatternValuePlace,
-    tx: PatternNonValuePlace,
+    pub tx: PatternNonValuePlace,
 }
 
+impl Pattern {
+    pub fn new(src: Option<SrcVar>,
+               e: PatternNonValuePlace,
+               a: PatternNonValuePlace,
+               v: PatternValuePlace,
+               tx: PatternNonValuePlace) -> Option<Pattern> {
+        let aa = a.clone();       // Too tired of fighting borrow scope for now.
+        if let PatternNonValuePlace::Ident(ref k) = aa {
+            if k.is_backward() {
+                // e and v have different types; we must convert them.
+                // Not every parseable value is suitable for the entity field!
+                // As such, this is a failable constructor.
+                let e_v = e.to_pattern_value_place();
+                if let Some(v_e) = v.to_pattern_non_value_place() {
+                    return Some(Pattern {
+                        source: src,
+                        entity: v_e,
+                        attribute: PatternNonValuePlace::Ident(k.to_reversed()),
+                        value: e_v,
+                        tx: tx,
+                    });
+                } else {
+                    return None;
+                }
+            }
+        }
+        Some(Pattern {
+            source: src,
+            entity: e,
+            attribute: a,
+            value: v,
+            tx: tx,
+        })
+    }
+}
+
+
 #[allow(dead_code)]
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub enum WhereClause {
-    /*
     Not,
     NotJoin,
     Or,
@@ -274,16 +408,17 @@ pub enum WhereClause {
     Pred,
     WhereFn,
     RuleExpr,
-    */
+    Pattern(Pattern),
-    Pattern,
 }
 
 #[allow(dead_code)]
-pub struct Query {
+#[derive(Clone, Debug, Eq, PartialEq)]
-    find: FindSpec,
+pub struct FindQuery {
-    with: Vec<Variable>,
+    pub find_spec: FindSpec,
-    in_vars: Vec<Variable>,
+    pub default_source: SrcVar,
-    in_sources: Vec<SrcVar>,
+    pub with: Vec<Variable>,
-    where_clauses: Vec<WhereClause>,
+    pub in_vars: Vec<Variable>,
+    pub in_sources: Vec<SrcVar>,
+    pub where_clauses: Vec<WhereClause>,
     // TODO: in_rules;
 }