implement lenient parser (#2129)

* move query parser to nom

* add suupport for term grouping

* initial work on infallible parser

* fmt

* add tests and fix minor parsing bugs

* address review comments

* add support for lenient queries in tantivy

* make lenient parser report errors

* allow mixing occur and bool in query

query-grammar/Cargo.toml

@@ -12,6 +12,4 @@ keywords = ["search", "information", "retrieval"]
 edition = "2021"
 
 [dependencies]
-combine = {version="4", default-features=false, features=[] }
-once_cell = "1.7.2"
-regex ={ version = "1.5.4", default-features = false, features = ["std", "unicode"] }
+nom = "7"

query-grammar/src/infallible.rs

@@ -0,0 +1,353 @@
+//! nom combinators for infallible operations
+
+use std::convert::Infallible;
+
+use nom::{AsChar, IResult, InputLength, InputTakeAtPosition};
+
+pub(crate) type ErrorList = Vec<LenientErrorInternal>;
+pub(crate) type JResult<I, O> = IResult<I, (O, ErrorList), Infallible>;
+
+/// An error, with an end-of-string based offset
+#[derive(Debug)]
+pub(crate) struct LenientErrorInternal {
+    pub pos: usize,
+    pub message: String,
+}
+
+/// A recoverable error and the position it happened at
+#[derive(Debug, PartialEq)]
+pub struct LenientError {
+    pub pos: usize,
+    pub message: String,
+}
+
+impl LenientError {
+    pub(crate) fn from_internal(internal: LenientErrorInternal, str_len: usize) -> LenientError {
+        LenientError {
+            pos: str_len - internal.pos,
+            message: internal.message,
+        }
+    }
+}
+
+fn unwrap_infallible<T>(res: Result<T, nom::Err<Infallible>>) -> T {
+    match res {
+        Ok(val) => val,
+        Err(_) => unreachable!(),
+    }
+}
+
+// when rfcs#1733 get stabilized, this can make things clearer
+// trait InfallibleParser<I, O> = nom::Parser<I, (O, ErrorList), std::convert::Infallible>;
+
+/// A variant of the classical `opt` parser, except it returns an infallible error type.
+///
+/// It's less generic than the original to ease type resolution in the rest of the code.
+pub(crate) fn opt_i<I: Clone, O, F>(mut f: F) -> impl FnMut(I) -> JResult<I, Option<O>>
+where F: nom::Parser<I, O, nom::error::Error<I>> {
+    move |input: I| {
+        let i = input.clone();
+        match f.parse(input) {
+            Ok((i, o)) => Ok((i, (Some(o), Vec::new()))),
+            Err(_) => Ok((i, (None, Vec::new()))),
+        }
+    }
+}
+
+pub(crate) fn opt_i_err<'a, I: Clone + InputLength, O, F>(
+    mut f: F,
+    message: impl ToString + 'a,
+) -> impl FnMut(I) -> JResult<I, Option<O>> + 'a
+where
+    F: nom::Parser<I, O, nom::error::Error<I>> + 'a,
+{
+    move |input: I| {
+        let i = input.clone();
+        match f.parse(input) {
+            Ok((i, o)) => Ok((i, (Some(o), Vec::new()))),
+            Err(_) => {
+                let errs = vec![LenientErrorInternal {
+                    pos: i.input_len(),
+                    message: message.to_string(),
+                }];
+                Ok((i, (None, errs)))
+            }
+        }
+    }
+}
+
+pub(crate) fn space0_infallible<T>(input: T) -> JResult<T, T>
+where
+    T: InputTakeAtPosition + Clone,
+    <T as InputTakeAtPosition>::Item: AsChar + Clone,
+{
+    opt_i(nom::character::complete::space0)(input)
+        .map(|(left, (spaces, errors))| (left, (spaces.expect("space0 can't fail"), errors)))
+}
+
+pub(crate) fn space1_infallible<T>(input: T) -> JResult<T, Option<T>>
+where
+    T: InputTakeAtPosition + Clone + InputLength,
+    <T as InputTakeAtPosition>::Item: AsChar + Clone,
+{
+    opt_i(nom::character::complete::space1)(input).map(|(left, (spaces, mut errors))| {
+        if spaces.is_none() {
+            errors.push(LenientErrorInternal {
+                pos: left.input_len(),
+                message: "missing space".to_string(),
+            })
+        }
+        (left, (spaces, errors))
+    })
+}
+
+pub(crate) fn fallible<I, O, E: nom::error::ParseError<I>, F>(
+    mut f: F,
+) -> impl FnMut(I) -> IResult<I, O, E>
+where F: nom::Parser<I, (O, ErrorList), Infallible> {
+    use nom::Err;
+    move |input: I| match f.parse(input) {
+        Ok((input, (output, _err))) => Ok((input, output)),
+        Err(Err::Incomplete(needed)) => Err(Err::Incomplete(needed)),
+        Err(Err::Error(val)) | Err(Err::Failure(val)) => match val {},
+    }
+}
+
+pub(crate) fn delimited_infallible<I, O1, O2, O3, F, G, H>(
+    mut first: F,
+    mut second: G,
+    mut third: H,
+) -> impl FnMut(I) -> JResult<I, O2>
+where
+    F: nom::Parser<I, (O1, ErrorList), Infallible>,
+    G: nom::Parser<I, (O2, ErrorList), Infallible>,
+    H: nom::Parser<I, (O3, ErrorList), Infallible>,
+{
+    move |input: I| {
+        let (input, (_, mut err)) = first.parse(input)?;
+        let (input, (o2, mut err2)) = second.parse(input)?;
+        err.append(&mut err2);
+        let (input, (_, mut err3)) = third.parse(input)?;
+        err.append(&mut err3);
+        Ok((input, (o2, err)))
+    }
+}
+
+// Parse nothing. Just a lazy way to not implement terminated/preceded and use delimited instead
+pub(crate) fn nothing(i: &str) -> JResult<&str, ()> {
+    Ok((i, ((), Vec::new())))
+}
+
+pub(crate) trait TupleInfallible<I, O> {
+    /// Parses the input and returns a tuple of results of each parser.
+    fn parse(&mut self, input: I) -> JResult<I, O>;
+}
+
+impl<Input, Output, F: nom::Parser<Input, (Output, ErrorList), Infallible>>
+    TupleInfallible<Input, (Output,)> for (F,)
+{
+    fn parse(&mut self, input: Input) -> JResult<Input, (Output,)> {
+        self.0.parse(input).map(|(i, (o, e))| (i, ((o,), e)))
+    }
+}
+
+// these macros are heavily copied from nom, with some minor adaptations for our type
+macro_rules! tuple_trait(
+  ($name1:ident $ty1:ident, $name2: ident $ty2:ident, $($name:ident $ty:ident),*) => (
+    tuple_trait!(__impl $name1 $ty1, $name2 $ty2; $($name $ty),*);
+  );
+  (__impl $($name:ident $ty: ident),+; $name1:ident $ty1:ident, $($name2:ident $ty2:ident),*) => (
+    tuple_trait_impl!($($name $ty),+);
+    tuple_trait!(__impl $($name $ty),+ , $name1 $ty1; $($name2 $ty2),*);
+  );
+  (__impl $($name:ident $ty: ident),+; $name1:ident $ty1:ident) => (
+    tuple_trait_impl!($($name $ty),+);
+    tuple_trait_impl!($($name $ty),+, $name1 $ty1);
+  );
+);
+
+macro_rules! tuple_trait_impl(
+  ($($name:ident $ty: ident),+) => (
+    impl<
+      Input: Clone, $($ty),+ ,
+      $($name: nom::Parser<Input, ($ty, ErrorList), Infallible>),+
+    > TupleInfallible<Input, ( $($ty),+ )> for ( $($name),+ ) {
+
+      fn parse(&mut self, input: Input) -> JResult<Input, ( $($ty),+ )> {
+        let mut error_list = Vec::new();
+        tuple_trait_inner!(0, self, input, (), error_list, $($name)+)
+      }
+    }
+  );
+);
+
+macro_rules! tuple_trait_inner(
+  ($it:tt, $self:expr, $input:expr, (), $error_list:expr, $head:ident $($id:ident)+) => ({
+    let (i, (o, mut err)) = $self.$it.parse($input.clone())?;
+    $error_list.append(&mut err);
+
+    succ!($it, tuple_trait_inner!($self, i, ( o ), $error_list, $($id)+))
+  });
+  ($it:tt, $self:expr, $input:expr, ($($parsed:tt)*), $error_list:expr, $head:ident $($id:ident)+) => ({
+    let (i, (o, mut err)) = $self.$it.parse($input.clone())?;
+    $error_list.append(&mut err);
+
+    succ!($it, tuple_trait_inner!($self, i, ($($parsed)* , o), $error_list, $($id)+))
+  });
+  ($it:tt, $self:expr, $input:expr, ($($parsed:tt)*), $error_list:expr, $head:ident) => ({
+    let (i, (o, mut err)) = $self.$it.parse($input.clone())?;
+    $error_list.append(&mut err);
+
+    Ok((i, (($($parsed)* , o), $error_list)))
+  });
+);
+
+macro_rules! succ (
+  (0, $submac:ident ! ($($rest:tt)*)) => ($submac!(1, $($rest)*));
+  (1, $submac:ident ! ($($rest:tt)*)) => ($submac!(2, $($rest)*));
+  (2, $submac:ident ! ($($rest:tt)*)) => ($submac!(3, $($rest)*));
+  (3, $submac:ident ! ($($rest:tt)*)) => ($submac!(4, $($rest)*));
+  (4, $submac:ident ! ($($rest:tt)*)) => ($submac!(5, $($rest)*));
+  (5, $submac:ident ! ($($rest:tt)*)) => ($submac!(6, $($rest)*));
+  (6, $submac:ident ! ($($rest:tt)*)) => ($submac!(7, $($rest)*));
+  (7, $submac:ident ! ($($rest:tt)*)) => ($submac!(8, $($rest)*));
+  (8, $submac:ident ! ($($rest:tt)*)) => ($submac!(9, $($rest)*));
+  (9, $submac:ident ! ($($rest:tt)*)) => ($submac!(10, $($rest)*));
+  (10, $submac:ident ! ($($rest:tt)*)) => ($submac!(11, $($rest)*));
+  (11, $submac:ident ! ($($rest:tt)*)) => ($submac!(12, $($rest)*));
+  (12, $submac:ident ! ($($rest:tt)*)) => ($submac!(13, $($rest)*));
+  (13, $submac:ident ! ($($rest:tt)*)) => ($submac!(14, $($rest)*));
+  (14, $submac:ident ! ($($rest:tt)*)) => ($submac!(15, $($rest)*));
+  (15, $submac:ident ! ($($rest:tt)*)) => ($submac!(16, $($rest)*));
+  (16, $submac:ident ! ($($rest:tt)*)) => ($submac!(17, $($rest)*));
+  (17, $submac:ident ! ($($rest:tt)*)) => ($submac!(18, $($rest)*));
+  (18, $submac:ident ! ($($rest:tt)*)) => ($submac!(19, $($rest)*));
+  (19, $submac:ident ! ($($rest:tt)*)) => ($submac!(20, $($rest)*));
+  (20, $submac:ident ! ($($rest:tt)*)) => ($submac!(21, $($rest)*));
+);
+
+tuple_trait!(FnA A, FnB B, FnC C, FnD D, FnE E, FnF F, FnG G, FnH H, FnI I, FnJ J, FnK K, FnL L,
+  FnM M, FnN N, FnO O, FnP P, FnQ Q, FnR R, FnS S, FnT T, FnU U);
+
+// Special case: implement `TupleInfallible` for `()`, the unit type.
+// This can come up in macros which accept a variable number of arguments.
+// Literally, `()` is an empty tuple, so it should simply parse nothing.
+impl<I> TupleInfallible<I, ()> for () {
+    fn parse(&mut self, input: I) -> JResult<I, ()> {
+        Ok((input, ((), Vec::new())))
+    }
+}
+
+pub(crate) fn tuple_infallible<I, O, List: TupleInfallible<I, O>>(
+    mut l: List,
+) -> impl FnMut(I) -> JResult<I, O> {
+    move |i: I| l.parse(i)
+}
+
+pub(crate) fn separated_list_infallible<I, O, O2, F, G>(
+    mut sep: G,
+    mut f: F,
+) -> impl FnMut(I) -> JResult<I, Vec<O>>
+where
+    I: Clone + InputLength,
+    F: nom::Parser<I, (O, ErrorList), Infallible>,
+    G: nom::Parser<I, (O2, ErrorList), Infallible>,
+{
+    move |i: I| {
+        let mut res: Vec<O> = Vec::new();
+        let mut errors: ErrorList = Vec::new();
+
+        let (mut i, (o, mut err)) = unwrap_infallible(f.parse(i.clone()));
+        errors.append(&mut err);
+        res.push(o);
+
+        loop {
+            let (i_sep_parsed, (_, mut err_sep)) = unwrap_infallible(sep.parse(i.clone()));
+            let len_before = i_sep_parsed.input_len();
+
+            let (i_elem_parsed, (o, mut err_elem)) =
+                unwrap_infallible(f.parse(i_sep_parsed.clone()));
+
+            // infinite loop check: the parser must always consume
+            // if we consumed nothing here, don't produce an element.
+            if i_elem_parsed.input_len() == len_before {
+                return Ok((i, (res, errors)));
+            }
+            res.push(o);
+            errors.append(&mut err_sep);
+            errors.append(&mut err_elem);
+            i = i_elem_parsed;
+        }
+    }
+}
+
+pub(crate) trait Alt<I, O> {
+    /// Tests each parser in the tuple and returns the result of the first one that succeeds
+    fn choice(&mut self, input: I) -> Option<JResult<I, O>>;
+}
+
+macro_rules! alt_trait(
+  ($first_cond:ident $first:ident, $($id_cond:ident $id: ident),+) => (
+    alt_trait!(__impl $first_cond $first; $($id_cond $id),+);
+  );
+  (__impl $($current_cond:ident $current:ident),*; $head_cond:ident $head:ident, $($id_cond:ident $id:ident),+) => (
+    alt_trait_impl!($($current_cond $current),*);
+
+    alt_trait!(__impl $($current_cond $current,)* $head_cond $head; $($id_cond $id),+);
+  );
+  (__impl $($current_cond:ident $current:ident),*; $head_cond:ident $head:ident) => (
+    alt_trait_impl!($($current_cond $current),*);
+    alt_trait_impl!($($current_cond $current,)* $head_cond $head);
+  );
+);
+
+macro_rules! alt_trait_impl(
+  ($($id_cond:ident $id:ident),+) => (
+    impl<
+      Input: Clone, Output,
+      $(
+          // () are to make things easier on me, but I'm not entirely sure whether we can do better
+          // with rule E0207
+          $id_cond: nom::Parser<Input, (), ()>,
+          $id: nom::Parser<Input, (Output, ErrorList), Infallible>
+      ),+
+    > Alt<Input, Output> for ( $(($id_cond, $id),)+ ) {
+
+      fn choice(&mut self, input: Input) -> Option<JResult<Input, Output>> {
+        match self.0.0.parse(input.clone()) {
+          Err(_) => alt_trait_inner!(1, self, input, $($id_cond $id),+),
+          Ok((input_left, _)) => Some(self.0.1.parse(input_left)),
+        }
+      }
+    }
+  );
+);
+
+macro_rules! alt_trait_inner(
+  ($it:tt, $self:expr, $input:expr, $head_cond:ident $head:ident, $($id_cond:ident $id:ident),+) => (
+    match $self.$it.0.parse($input.clone()) {
+      Err(_) => succ!($it, alt_trait_inner!($self, $input, $($id_cond $id),+)),
+      Ok((input_left, _)) => Some($self.$it.1.parse(input_left)),
+    }
+  );
+  ($it:tt, $self:expr, $input:expr, $head_cond:ident $head:ident) => (
+    None
+  );
+);
+
+alt_trait!(A1 A, B1 B, C1 C, D1 D, E1 E, F1 F, G1 G, H1 H, I1 I, J1 J, K1 K,
+           L1 L, M1 M, N1 N, O1 O, P1 P, Q1 Q, R1 R, S1 S, T1 T, U1 U);
+
+/// An alt() like combinator. For each branch, it first tries a fallible parser, which commits to
+/// this branch, or tells to check next branch, and the execute the infallible parser which follow.
+///
+/// In case no branch match, the default (fallible) parser is executed.
+pub(crate) fn alt_infallible<I: Clone, O, F, List: Alt<I, O>>(
+    mut l: List,
+    mut default: F,
+) -> impl FnMut(I) -> JResult<I, O>
+where
+    F: nom::Parser<I, (O, ErrorList), Infallible>,
+{
+    move |i: I| l.choice(i.clone()).unwrap_or_else(|| default.parse(i))
+}

query-grammar/src/lib.rs

@@ -1,19 +1,26 @@
 #![allow(clippy::derive_partial_eq_without_eq)]
 
+mod infallible;
 mod occur;
 mod query_grammar;
 mod user_input_ast;
-use combine::parser::Parser;
 
+pub use crate::infallible::LenientError;
 pub use crate::occur::Occur;
-use crate::query_grammar::parse_to_ast;
+use crate::query_grammar::{parse_to_ast, parse_to_ast_lenient};
 pub use crate::user_input_ast::{
     Delimiter, UserInputAst, UserInputBound, UserInputLeaf, UserInputLiteral,
 };
 
 pub struct Error;
 
+/// Parse a query
 pub fn parse_query(query: &str) -> Result<UserInputAst, Error> {
-    let (user_input_ast, _remaining) = parse_to_ast().parse(query).map_err(|_| Error)?;
+    let (_remaining, user_input_ast) = parse_to_ast(query).map_err(|_| Error)?;
     Ok(user_input_ast)
 }
+
+/// Parse a query, trying to recover from syntax errors, and giving hints toward fixing errors.
+pub fn parse_query_lenient(query: &str) -> (UserInputAst, Vec<LenientError>) {
+    parse_to_ast_lenient(query)
+}