Add utilities for defining parsers. (#218) r=vporof
satisfy_unwrap and ResultParser go into mentat_parser_utils.
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3 changed files with 98 additions and 2 deletions
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@ -1,6 +1,7 @@
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[package]
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[package]
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name = "mentat_parser_utils"
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name = "mentat_parser_utils"
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version = "0.1.0"
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version = "0.1.0"
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authors = ["Victor Porof <vporof@mozilla.com>"]
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authors = ["Victor Porof <vporof@mozilla.com>", "Richard Newman <rnewman@mozilla.com>"]
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[dependencies]
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[dependencies]
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combine = "2.1.1"
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations under the License.
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// specific language governing permissions and limitations under the License.
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extern crate combine;
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use combine::ParseResult;
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use combine::combinator::{Expected, FnParser};
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// A type definition for a function parser that either parses an `O` from an input stream of type
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// `I`, or fails with an "expected" failure.
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// See <https://docs.rs/combine/2.2.1/combine/trait.Parser.html#method.expected> for more
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// illumination.
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// Nothing about this is specific to the result type of the parser.
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pub type ResultParser<O, I> = Expected<FnParser<I, fn(I) -> ParseResult<O, I>>>;
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/// `assert_parses_to!` simplifies some of the boilerplate around running a
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/// `assert_parses_to!` simplifies some of the boilerplate around running a
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/// parser function against input and expecting a certain result.
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/// parser function against input and expecting a certain result.
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#[macro_export]
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#[macro_export]
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@ -17,4 +29,13 @@ macro_rules! assert_parses_to {
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let result = par.parse(&$input[..]);
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let result = par.parse(&$input[..]);
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assert_eq!(result, Ok(($expected, &[][..])));
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assert_eq!(result, Ok(($expected, &[][..])));
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}}
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}}
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}
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}
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/// `satisfy_unwrap!` makes it a little easier to implement a `satisfy_map`
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/// body that matches a particular `Value` enum case, otherwise returning `None`.
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#[macro_export]
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macro_rules! satisfy_unwrap {
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( $cas: path, $var: ident, $body: block ) => {
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satisfy_map(|x: edn::Value| if let $cas($var) = x $body else { None })
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}
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}
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74
query-parser/src/parser_util.rs
Normal file
74
query-parser/src/parser_util.rs
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// Copyright 2016 Mozilla
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
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// this file except in compliance with the License. You may obtain a copy of the
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// License at http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed
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// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
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// CONDITIONS OF ANY KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations under the License.
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extern crate combine;
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extern crate edn;
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extern crate mentat_query;
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/// Generate a `satisfy_map` expression that matches a `PlainSymbol`
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/// value with the given name.
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///
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/// We do this rather than using `combine::token` so that we don't
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/// need to allocate a new `String` inside a `PlainSymbol` inside a `Value`
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/// just to match input.
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macro_rules! matches_plain_symbol {
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($name: expr, $input: ident) => {
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satisfy_map(|x: edn::Value| {
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if let edn::Value::PlainSymbol(ref s) = x {
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if s.0.as_str() == $name {
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return Some(());
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}
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}
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return None;
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}).parse_stream($input)
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}
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}
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/// Define an `impl` body for the `$parser` type. The body will contain a parser
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/// function called `$name`, consuming a stream of `$item_type`s. The parser's
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/// result type will be `$result_type`.
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///
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/// The provided `$body` will be evaluated with `$input` bound to the input stream.
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///
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/// `$body`, when run, should return a `ParseResult` of the appropriate result type.
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macro_rules! def_parser_fn {
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( $parser: ident, $name: ident, $item_type: ty, $result_type: ty, $input: ident, $body: block ) => {
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impl<I> $parser<I> where I: Stream<Item = $item_type> {
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fn $name() -> ResultParser<$result_type, I> {
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fn inner<I: Stream<Item = $item_type>>($input: I) -> ParseResult<$result_type, I> {
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$body
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}
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parser(inner as fn(I) -> ParseResult<$result_type, I>).expected("$name")
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}
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}
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}
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}
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/// `def_value_parser_fn` is a short-cut to `def_parser_fn` with the input type
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/// being `edn::Value`.
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macro_rules! def_value_parser_fn {
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( $parser: ident, $name: ident, $result_type: ty, $input: ident, $body: block ) => {
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def_parser_fn!($parser, $name, edn::Value, $result_type, $input, $body);
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}
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}
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/// `def_value_satisfy_parser_fn` is a short-cut to `def_parser_fn` with the input type
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/// being `edn::Value` and the body being a call to `satisfy_map` with the given transformer.
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///
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/// In practice this allows you to simply pass a function that accepts an `&edn::Value` and
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/// returns an `Option<$result_type>`: if a suitable value is at the front of the stream,
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/// it will be converted and returned by the parser; otherwise, the parse will fail.
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macro_rules! def_value_satisfy_parser_fn {
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( $parser: ident, $name: ident, $result_type: ty, $transformer: path ) => {
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def_value_parser_fn!($parser, $name, $result_type, input, {
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satisfy_map(|x: edn::Value| $transformer(&x)).parse_stream(input)
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});
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}
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}
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