mentat/edn/src/lib.rs

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// 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 chrono;
extern crate itertools;
extern crate num;
extern crate ordered_float;
extern crate pretty;
extern crate peg;
extern crate uuid;
#[cfg(feature = "serde_support")]
extern crate serde;
#[cfg(feature = "serde_support")]
#[macro_use]
extern crate serde_derive;
pub mod entities;
pub mod intern_set;
pub use intern_set::InternSet;
// Intentionally not pub.
pub mod matcher;
mod namespaceable_name;
pub mod pretty_print;
pub mod query;
pub mod symbols;
pub mod types;
pub mod utils;
pub mod value_rc;
pub use value_rc::{Cloned, FromRc, ValueRc};
// Re-export the types we use.
pub use chrono::{DateTime, Utc};
pub use num::BigInt;
Extract partial storage abstraction; use error-chain throughout. Fixes #328. r=rnewman (#341) * Pre: Drop unneeded tx0 from search results. * Pre: Don't require a schema in some of the DB code. The idea is to separate the transaction applying code, which is schema-aware, from the concrete storage code, which is just concerned with getting bits onto disk. * Pre: Only reference Schema, not DB, in debug module. This is part of a larger separation of the volatile PartitionMap, which is modified every transaction, from the stable Schema, which is infrequently modified. * Pre: Fix indentation. * Extract part of DB to new SchemaTypeChecking trait. * Extract part of DB to new PartitionMapping trait. * Pre: Don't expect :db.part/tx partition to advance when tx fails. This fails right now, because we allocate tx IDs even when we shouldn't. * Sketch a db interface without DB. * Add ValueParseError; use error-chain in tx-parser. This can be simplified when https://github.com/Marwes/combine/issues/86 makes it to a published release, but this unblocks us for now. This converts the `combine` error type `ParseError<&'a [edn::Value]>` to a type with owned `Vec<edn::Value>` collections, re-using `edn::Value::Vector` for making them `Display`. * Pre: Accept Borrow<Schema> instead of just &Schema in debug module. This makes it easy to use Rc<Schema> or Arc<Schema> without inserting &* sigils throughout the code. * Use error-chain in query-parser. There are a few things to point out here: - the fine grained error types have been flattened into one crate-wide error type; it's pretty easy to regain the granularity as needed. - edn::ParseError is automatically lifted to mentat_query_parser::errors::Error; - we use mentat_parser_utils::ValueParser to maintain parsing error information from `combine`. * Patch up top-level. * Review comment: Only `borrow()` once.
2017-02-24 23:32:41 +00:00
pub use ordered_float::OrderedFloat;
pub use uuid::Uuid;
// Export from our modules.
pub use types::{
FromMicros, FromMillis, Span, SpannedValue, ToMicros, ToMillis, Value, ValueAndSpan,
};
pub use symbols::{Keyword, NamespacedSymbol, PlainSymbol};
use std::collections::{BTreeSet, BTreeMap, LinkedList};
use std::iter::FromIterator;
use std::f64::{NAN, INFINITY, NEG_INFINITY};
use chrono::{
TimeZone,
};
use entities::*;
use query::FromValue;
// Goal: Be able to parse https://github.com/edn-format/edn
// Also extensible to help parse http://docs.datomic.com/query.html
// Debugging hint: test using `cargo test --features peg/trace -- --nocapture`
// to trace where the parser is failing
// TODO: Support tagged elements
// TODO: Support discard
pub type ParseError = peg::error::ParseError<peg::str::LineCol>;
peg::parser!(pub grammar parse() for str {
// Clojure (and thus EDN) regards commas as whitespace, and thus the two-element vectors [1 2] and
// [1,,,,2] are equivalent, as are the maps {:a 1, :b 2} and {:a 1 :b 2}.
rule whitespace() = quiet!{[' ' | '\r' | '\n' | '\t' | ',']}
rule comment() = quiet!{";" (!['\r' | '\n'][_])* ['\r' | '\n']?}
rule __() = whitespace() / comment()*
pub rule nil() -> SpannedValue = "nil" { SpannedValue::Nil }
pub rule nan() -> SpannedValue = "#f" whitespace()+ "NaN" { SpannedValue::Float(OrderedFloat(NAN)) }
pub rule infinity() -> SpannedValue = "#f" whitespace()+ s:$(sign()) "Infinity"
{ SpannedValue::Float(OrderedFloat(if s == "+" { INFINITY } else { NEG_INFINITY })) }
pub rule boolean() -> SpannedValue
= "true" { SpannedValue::Boolean(true) }
/ "false" { SpannedValue::Boolean(false) }
rule digit() = ['0'..='9']
rule alphanumeric() = ['0'..='9' | 'a'..='z' | 'A'..='Z']
rule octaldigit() = ['0'..='7']
rule validbase() = ['3']['0'..='6'] / ['1' | '2']['0'..='9'] / ['2'..='9']
rule hex() = ['0'..='9' | 'a'..='f' | 'A'..='F']
rule sign() = ['+' | '-']
pub rule raw_bigint() -> BigInt = b:$( sign()? digit()+ ) "N"
{ b.parse::<BigInt>().unwrap() }
pub rule raw_octalinteger() -> i64 = "0" i:$( octaldigit()+ )
{ i64::from_str_radix(i, 8).unwrap() }
pub rule raw_hexinteger() -> i64 = "0x" i:$( hex()+ )
{ i64::from_str_radix(i, 16).unwrap() }
pub rule raw_basedinteger() -> i64 = b:$( validbase() ) "r" i:$( alphanumeric()+ )
{ i64::from_str_radix(i, b.parse::<u32>().unwrap()).unwrap() }
pub rule raw_integer() -> i64 = i:$( sign()? digit()+ ) !("." / (['e' | 'E']))
{ i.parse::<i64>().unwrap() }
pub rule raw_float() -> OrderedFloat<f64> = f:$(sign()? digit()+ ("." digit()+)? (['e' | 'E'] sign()? digit()+)?)
{ OrderedFloat(f.parse::<f64>().unwrap()) }
pub rule bigint() -> SpannedValue = v:raw_bigint() { SpannedValue::BigInteger(v) }
pub rule octalinteger() -> SpannedValue = v:raw_octalinteger() { SpannedValue::Integer(v) }
pub rule hexinteger() -> SpannedValue = v:raw_hexinteger() { SpannedValue::Integer(v) }
pub rule basedinteger() -> SpannedValue = v:raw_basedinteger() { SpannedValue::Integer(v) }
pub rule integer() -> SpannedValue = v:raw_integer() { SpannedValue::Integer(v) }
pub rule float() -> SpannedValue = v:raw_float() { SpannedValue::Float(v) }
rule number() -> SpannedValue = ( bigint() / basedinteger() / hexinteger() / octalinteger() / integer() / float() )
// TODO: standalone characters: \<char>, \newline, \return, \space and \tab.
// rule string_standalone_chars() ->
rule string_special_char() -> &'input str = c:$( "\\" $(['\\' | '"' | 'n' | 't' | 'r']) ) { c }
rule string_normal_chars() -> &'input str = c:$(['^' | '"' | '\\' ]+) { c }
// This is what we need to do in order to unescape. We can't just match the entire string slice:
// we get a Vec<&str> from rust-peg, where some of the parts might be unescaped special characters,
// and we join it together to form an output string.
// E.g., input = r#"\"foo\\\\bar\""#
// output = [quote, "foo", backslash, "bar", quote]
// result = r#""foo\\bar""#
// For the typical case, string_normal_chars will match multiple, leading to a single-element vec.
pub rule raw_text() -> String = "\"" t:((string_special_char() / string_normal_chars())*) "\""
{ t.join(&"").to_string() }
pub rule text() -> SpannedValue
= v:raw_text() { SpannedValue::Text(v) }
// RFC 3339 timestamps. #inst "1985-04-12T23:20:50.52Z"
// We accept an arbitrary depth of decimals.
// TODO: Note that we discard the timezone information -- all times are translated to UTC. Should we?
rule inst_string() -> DateTime<Utc> =
"#inst" whitespace()+ "\"" d:$( ['0'..='9']*<4> "-" ['0'..='2']['0'..='9'] "-" ['0'..='3']['0'..='9']
"T"
['0'..='2']['0'..='9'] ":" ['0'..='5']['0'..='9'] ":" ['0'..='6']['0'..='9']
("." ['0'..='9']+)?
("Z" / (("+" / "-") ['0'..='2']['0'..='9'] ":" ['0'..='5']['0'..='9']))
)
"\"" {?
DateTime::parse_from_rfc3339(d)
.map(|t| t.with_timezone(&Utc))
.map_err(|_| "invalid datetime") // TODO Oh, rustpeg.
}
rule inst_micros() -> DateTime<Utc> =
"#instmicros" whitespace()+ d:$( digit()+ ) {
let micros = d.parse::<i64>().unwrap();
let seconds: i64 = micros / 1000000;
let nanos: u32 = ((micros % 1000000).abs() as u32) * 1000;
Utc.timestamp(seconds, nanos)
}
rule inst_millis() -> DateTime<Utc> =
"#instmillis" whitespace()+ d:$( digit()+ ) {
let millis = d.parse::<i64>().unwrap();
let seconds: i64 = millis / 1000;
let nanos: u32 = ((millis % 1000).abs() as u32) * 1000000;
Utc.timestamp(seconds, nanos)
}
rule inst() -> SpannedValue = t:(inst_millis() / inst_micros() / inst_string())
{ SpannedValue::Instant(t) }
rule uuid_string() -> Uuid =
"\"" u:$( ['a'..='f' | '0'..='9']*<8> "-" ['a'..='f' | '0'..='9']*<4> "-" ['a'..='f' | '0'..='9']*<4> "-" ['a'..='f' | '0'..='9']*<4> "-" ['a'..='f' | '0'..='9']*<12> ) "\"" {
Uuid::parse_str(u).expect("this is a valid UUID string")
}
pub rule uuid() -> SpannedValue = "#uuid" whitespace()+ u:uuid_string()
{ SpannedValue::Uuid(u) }
rule namespace_divider() = "."
rule namespace_separator() = "/"
// TODO: Be more picky here.
// Keywords follow the rules of symbols, except they can (and must) begin with :
// e.g. :fred or :my/fred. See https://github.com/edn-format/edn#keywords
rule symbol_char_initial() = ['a'..='z' | 'A'..='Z' | '0'..='9' | '*' | '!' | '_' | '?' | '$' | '%' | '&' | '=' | '<' | '>']
rule symbol_char_subsequent() = ['+' | 'a'..='z' | 'A'..='Z' | '0'..='9' | '*' | '!' | '_' | '?' | '$' | '%' | '&' | '=' | '<' | '>' | '-']
rule symbol_namespace() = symbol_char_initial() symbol_char_subsequent()* (namespace_divider() symbol_char_subsequent()+)*
rule symbol_name() = ( symbol_char_initial()+ symbol_char_subsequent()* )
rule plain_symbol_name() = symbol_name() / "..." / "."
rule keyword_prefix() = ":"
pub rule symbol() -> SpannedValue =
ns:( sns:$(symbol_namespace()) namespace_separator() { sns })?
n:$(plain_symbol_name())
{ SpannedValue::from_symbol(ns, n) }
/ expected!("symbol")
pub rule keyword() -> SpannedValue =
keyword_prefix()
ns:( sns:$(symbol_namespace()) namespace_separator() { sns })?
n:$(symbol_name())
{ SpannedValue::from_keyword(ns, n) }
/ expected!("keyword")
pub rule list() -> SpannedValue = "(" __ v:(value())* __ ")"
{ SpannedValue::List(LinkedList::from_iter(v)) }
pub rule vector() -> SpannedValue = "[" __ v:(value())* __ "]"
{ SpannedValue::Vector(v) }
pub rule set() -> SpannedValue = "#{" __ v:(value())* __ "}"
{ SpannedValue::Set(BTreeSet::from_iter(v)) }
pub rule pair() -> (ValueAndSpan, ValueAndSpan) =
k:(value()) v:(value()) {
(k, v)
}
pub rule map() -> SpannedValue = "{" __ v:(pair())* __ "}"
{ SpannedValue::Map(BTreeMap::from_iter(v)) }
// Note: It's important that float comes before integer or the parser assumes that floats are integers and fails to parse.
pub rule value() -> ValueAndSpan =
__ start:position!() v:(nil() / nan() / infinity() / boolean() / number() / inst() / uuid() / text() / keyword() / symbol() / list() / vector() / map() / set()) end:position!() __ {
ValueAndSpan {
inner: v,
span: Span::new(start, end)
}
}
/ expected!("value")
rule atom() -> ValueAndSpan
= v:value() {? if v.is_atom() { Ok(v) } else { Err("expected atom") } }
// Transaction entity parser starts here.
pub rule op() -> OpType
= ":db/add" { OpType::Add }
/ ":db/retract" { OpType::Retract }
rule raw_keyword() -> Keyword =
keyword_prefix()
ns:( sns:$(symbol_namespace()) namespace_separator() { sns })?
n:$(symbol_name()) {
match ns {
Some(ns) => Keyword::namespaced(ns, n),
None => Keyword::plain(n),
}
}
/ expected!("keyword")
rule raw_forward_keyword() -> Keyword
= v:raw_keyword() {? if v.is_forward() { Ok(v) } else { Err("expected :forward or :forward/keyword") } }
rule raw_backward_keyword() -> Keyword
= v:raw_keyword() {? if v.is_backward() { Ok(v) } else { Err("expected :_backward or :backward/_keyword") } }
rule raw_namespaced_keyword() -> Keyword
= keyword_prefix() ns:$(symbol_namespace()) namespace_separator() n:$(symbol_name()) { Keyword::namespaced(ns, n) }
/ expected!("namespaced keyword")
rule raw_forward_namespaced_keyword() -> Keyword
= v:raw_namespaced_keyword() {? if v.is_forward() { Ok(v) } else { Err("expected namespaced :forward/keyword") } }
rule raw_backward_namespaced_keyword() -> Keyword
= v:raw_namespaced_keyword() {? if v.is_backward() { Ok(v) } else { Err("expected namespaced :backward/_keyword") } }
rule entid() -> EntidOrIdent
= v:( raw_basedinteger() / raw_hexinteger() / raw_octalinteger() / raw_integer() ) { EntidOrIdent::Entid(v) }
/ v:raw_namespaced_keyword() { EntidOrIdent::Ident(v) }
/ expected!("entid")
rule forward_entid() -> EntidOrIdent
= v:( raw_basedinteger() / raw_hexinteger() / raw_octalinteger() / raw_integer() ) { EntidOrIdent::Entid(v) }
/ v:raw_forward_namespaced_keyword() { EntidOrIdent::Ident(v) }
/ expected!("forward entid")
rule backward_entid() -> EntidOrIdent
= v:raw_backward_namespaced_keyword() { EntidOrIdent::Ident(v.to_reversed()) }
/ expected!("backward entid")
rule lookup_ref() -> LookupRef<ValueAndSpan>
= "(" __ "lookup-ref" __ a:(entid()) __ v:(value()) __ ")" { LookupRef { a: AttributePlace::Entid(a), v } }
/ expected!("lookup-ref")
rule tx_function() -> TxFunction
= "(" __ n:$(symbol_name()) __ ")" { TxFunction { op: PlainSymbol::plain(n) } }
rule entity_place() -> EntityPlace<ValueAndSpan>
= v:raw_text() { EntityPlace::TempId(TempId::External(v).into()) }
/ v:entid() { EntityPlace::Entid(v) }
/ v:lookup_ref() { EntityPlace::LookupRef(v) }
/ v:tx_function() { EntityPlace::TxFunction(v) }
rule value_place_pair() -> (EntidOrIdent, ValuePlace<ValueAndSpan>)
= k:(entid()) __ v:(value_place()) { (k, v) }
rule map_notation() -> MapNotation<ValueAndSpan>
= "{" __ kvs:(value_place_pair()*) __ "}" { kvs.into_iter().collect() }
rule value_place() -> ValuePlace<ValueAndSpan>
= __ v:lookup_ref() __ { ValuePlace::LookupRef(v) }
/ __ v:tx_function() __ { ValuePlace::TxFunction(v) }
/ __ "[" __ vs:(value_place()*) __ "]" __ { ValuePlace::Vector(vs) }
/ __ v:map_notation() __ { ValuePlace::MapNotation(v) }
/ __ v:atom() __ { ValuePlace::Atom(v) }
pub rule entity() -> Entity<ValueAndSpan>
= __ "[" __ op:(op()) __ e:(entity_place()) __ a:(forward_entid()) __ v:(value_place()) __ "]" __ { Entity::AddOrRetract { op, e: e, a: AttributePlace::Entid(a), v: v } }
/ __ "[" __ op:(op()) __ e:(value_place()) __ a:(backward_entid()) __ v:(entity_place()) __ "]" __ { Entity::AddOrRetract { op, e: v, a: AttributePlace::Entid(a), v: e } }
/ __ map:map_notation() __ { Entity::MapNotation(map) }
/ expected!("entity")
pub rule entities() -> Vec<Entity<ValueAndSpan>>
= __ "[" __ es:(entity()*) __ "]" __ { es }
// Query parser starts here.
//
// We expect every rule except the `raw_*` rules to eat whitespace
// (with `__`) at its start and finish. That means that every string
// pattern (say "[") should be bracketed on either side with either a
// whitespace-eating rule or an explicit whitespace eating `__`.
rule query_function() -> query::QueryFunction
= __ n:$(symbol_name()) __ {? query::QueryFunction::from_symbol(&PlainSymbol::plain(n)).ok_or("expected query function") }
rule fn_arg() -> query::FnArg
= v:value() {? query::FnArg::from_value(&v).ok_or("expected query function argument") }
/ __ "[" args:fn_arg()+ "]" __ { query::FnArg::Vector(args) }
rule find_elem() -> query::Element
= __ v:variable() __ { query::Element::Variable(v) }
/ __ "(" __ "the" v:variable() ")" __ { query::Element::Corresponding(v) }
/ __ "(" __ "pull" var:variable() "[" patterns:pull_attribute()+ "]" __ ")" __ { query::Element::Pull(query::Pull { var, patterns }) }
/ __ "(" func:query_function() args:fn_arg()* ")" __ { query::Element::Aggregate(query::Aggregate { func, args }) }
rule find_spec() -> query::FindSpec
= f:find_elem() "." __ { query::FindSpec::FindScalar(f) }
/ fs:find_elem()+ { query::FindSpec::FindRel(fs) }
/ __ "[" f:find_elem() __ "..." __ "]" __ { query::FindSpec::FindColl(f) }
/ __ "[" fs:find_elem()+ "]" __ { query::FindSpec::FindTuple(fs) }
rule pull_attribute() -> query::PullAttributeSpec
= __ "*" __ { query::PullAttributeSpec::Wildcard }
/ __ k:raw_forward_namespaced_keyword() __ alias:(":as" __ alias:raw_forward_keyword() __ { alias })? {
let attribute = query::PullConcreteAttribute::Ident(::std::rc::Rc::new(k));
let alias = alias.map(|alias| ::std::rc::Rc::new(alias));
query::PullAttributeSpec::Attribute(
query::NamedPullAttribute {
attribute,
alias: alias,
})
}
rule limit() -> query::Limit
= __ v:variable() __ { query::Limit::Variable(v) }
/ __ n:(raw_octalinteger() / raw_hexinteger() / raw_basedinteger() / raw_integer()) __ {?
if n > 0 {
Ok(query::Limit::Fixed(n as u64))
} else {
Err("expected positive integer")
}
}
rule order() -> query::Order
= __ "(" __ "asc" v:variable() ")" __ { query::Order(query::Direction::Ascending, v) }
/ __ "(" __ "desc" v:variable() ")" __ { query::Order(query::Direction::Descending, v) }
/ v:variable() { query::Order(query::Direction::Ascending, v) }
rule pattern_value_place() -> query::PatternValuePlace
= v:value() {? query::PatternValuePlace::from_value(&v).ok_or("expected pattern_value_place") }
rule pattern_non_value_place() -> query::PatternNonValuePlace
= v:value() {? query::PatternNonValuePlace::from_value(&v).ok_or("expected pattern_non_value_place") }
rule pattern() -> query::WhereClause
= __ "["
src:src_var()?
e:pattern_non_value_place()
a:pattern_non_value_place()
v:pattern_value_place()?
tx:pattern_non_value_place()?
"]" __
{?
let v = v.unwrap_or(query::PatternValuePlace::Placeholder);
let tx = tx.unwrap_or(query::PatternNonValuePlace::Placeholder);
// Pattern::new takes care of reversal of reversed
// attributes: [?x :foo/_bar ?y] turns into
// [?y :foo/bar ?x].
//
// 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 a nested optional, which we unwrap here.
query::Pattern::new(src, e, a, v, tx)
.map(query::WhereClause::Pattern)
.ok_or("expected pattern")
}
// TODO: This shouldn't be checked at parse time.
rule rule_vars() -> BTreeSet<query::Variable>
= vs:variable()+ {?
let given = vs.len();
let set: BTreeSet<query::Variable> = vs.into_iter().collect();
if given != set.len() {
Err("expected unique variables")
} else {
Ok(set)
}
}
rule or_pattern_clause() -> query::OrWhereClause
= clause:where_clause() { query::OrWhereClause::Clause(clause) }
rule or_and_clause() -> query::OrWhereClause
= __ "(" __ "and" clauses:where_clause()+ ")" __ { query::OrWhereClause::And(clauses) }
rule or_where_clause() -> query::OrWhereClause
= or_pattern_clause()
/ or_and_clause()
rule or_clause() -> query::WhereClause
= __ "(" __ "or" clauses:or_where_clause()+ ")" __ {
query::WhereClause::OrJoin(query::OrJoin::new(query::UnifyVars::Implicit, clauses))
}
rule or_join_clause() -> query::WhereClause
= __ "(" __ "or-join" __ "[" vars:rule_vars() "]" clauses:or_where_clause()+ ")" __ {
query::WhereClause::OrJoin(query::OrJoin::new(query::UnifyVars::Explicit(vars), clauses))
}
rule not_clause() -> query::WhereClause
= __ "(" __ "not" clauses:where_clause()+ ")" __ {
query::WhereClause::NotJoin(query::NotJoin::new(query::UnifyVars::Implicit, clauses))
}
rule not_join_clause() -> query::WhereClause
= __ "(" __ "not-join" __ "[" vars:rule_vars() "]" clauses:where_clause()+ ")" __ {
query::WhereClause::NotJoin(query::NotJoin::new(query::UnifyVars::Explicit(vars), clauses))
}
rule type_annotation() -> query::WhereClause
= __ "[" __ "(" __ "type" var:variable() __ ty:raw_keyword() __ ")" __ "]" __ {
query::WhereClause::TypeAnnotation(
query::TypeAnnotation {
value_type: ty,
variable: var,
})
}
rule pred() -> query::WhereClause
= __ "[" __ "(" func:query_function() args:fn_arg()* ")" __ "]" __ {
query::WhereClause::Pred(
query::Predicate {
operator: func.0,
args: args,
})
}
pub rule where_fn() -> query::WhereClause
= __ "[" __ "(" func:query_function() args:fn_arg()* ")" __ binding:binding() "]" __ {
query::WhereClause::WhereFn(
query::WhereFn {
operator: func.0,
args: args,
binding,
})
}
rule where_clause() -> query::WhereClause
// Right now we only support patterns and predicates. See #239 for more.
= pattern()
/ or_join_clause()
/ or_clause()
/ not_join_clause()
/ not_clause()
/ type_annotation()
/ pred()
/ where_fn()
rule query_part() -> query::QueryPart
= __ ":find" fs:find_spec() { query::QueryPart::FindSpec(fs) }
/ __ ":in" in_vars:variable()+ { query::QueryPart::InVars(in_vars) }
/ __ ":limit" l:limit() { query::QueryPart::Limit(l) }
/ __ ":order" os:order()+ { query::QueryPart::Order(os) }
/ __ ":where" ws:where_clause()+ { query::QueryPart::WhereClauses(ws) }
/ __ ":with" with_vars:variable()+ { query::QueryPart::WithVars(with_vars) }
pub rule parse_query() -> query::ParsedQuery
= __ "[" qps:query_part()+ "]" __ {? query::ParsedQuery::from_parts(qps) }
rule variable() -> query::Variable
= v:value() {? query::Variable::from_value(&v).ok_or("expected variable") }
rule src_var() -> query::SrcVar
= v:value() {? query::SrcVar::from_value(&v).ok_or("expected src_var") }
rule variable_or_placeholder() -> query::VariableOrPlaceholder
= v:variable() { query::VariableOrPlaceholder::Variable(v) }
/ __ "_" __ { query::VariableOrPlaceholder::Placeholder }
rule binding() -> query::Binding
= __ "[" __ "[" vs:variable_or_placeholder()+ "]" __ "]" __ { query::Binding::BindRel(vs) }
/ __ "[" v:variable() "..." __ "]" __ { query::Binding::BindColl(v) }
/ __ "[" vs:variable_or_placeholder()+ "]" __ { query::Binding::BindTuple(vs) }
/ v:variable() { query::Binding::BindScalar(v) }
});