feat(toml): Add DeTable::parse_recoverable (#953)

I had considered naming this new method `parse` and the `Result` method
`try_parse` but the `Result` method should be the default / go-to for
people and so the shorter name that matches similar functions is a
better choice.

`recovery` felt odd.

Having it after `parse`, instead of `recoverable_parse`, keeps the
emphasis on the most important part.

Fixes #371

Author: epage

Cargo.lock

@@ -65,6 +65,7 @@ toml-test-harness = { version = "1.3.2", features = ["snapshot"] }
 toml-test-data = "2.3.0"
 snapbox = "0.6.0"
 walkdir = "2.5.0"
+itertools = "0.14.0"
 
 [[test]]
 name = "decoder_compliance"

crates/toml/Cargo.toml

@@ -2,6 +2,7 @@ use alloc::borrow::Cow;
 
 use serde_spanned::Spanned;
 
+use crate::alloc_prelude::*;
 use crate::de::DeString;
 use crate::de::DeValue;
 use crate::map::Map;
@@ -27,6 +28,14 @@ impl<'i> DeTable<'i> {
         }
     }
 
+    /// Parse a TOML document, with best effort recovery on error
+    pub fn parse_recoverable(input: &'i str) -> (Spanned<Self>, Vec<crate::de::Error>) {
+        let source = toml_parse::Source::new(input);
+        let mut errors = crate::de::error::TomlSink::<Vec<_>>::new(source);
+        let value = crate::de::parser::parse_document(source, &mut errors);
+        (value, errors.into_inner())
+    }
+
     /// Ensure no data is borrowed
     pub fn make_owned(&mut self) {
         let borrowed = core::mem::take(self);

crates/toml/src/de/detable.rs

@@ -34,7 +34,7 @@ pub enum DeValue<'i> {
 }
 
 impl<'i> DeValue<'i> {
-    /// Parse a TOML document
+    /// Parse a TOML value
     pub fn parse(input: &'i str) -> Result<Spanned<Self>, crate::de::Error> {
         let source = toml_parse::Source::new(input);
         let mut errors = crate::de::error::TomlSink::<Option<_>>::new(source);
@@ -46,6 +46,14 @@ impl<'i> DeValue<'i> {
         }
     }
 
+    /// Parse a TOML value, with best effort recovery on error
+    pub fn parse_recoverable(input: &'i str) -> (Spanned<Self>, Vec<crate::de::Error>) {
+        let source = toml_parse::Source::new(input);
+        let mut errors = crate::de::error::TomlSink::<Vec<_>>::new(source);
+        let value = crate::de::parser::parse_value(source, &mut errors);
+        (value, errors.into_inner())
+    }
+
     /// Ensure no data is borrowed
     pub fn make_owned(&mut self) {
         match self {

crates/toml/src/de/devalue.rs

@@ -13,9 +13,17 @@ impl toml_test_harness::Decoder for Decoder {
         &self,
         data: &[u8],
     ) -> Result<toml_test_harness::DecodedValue, toml_test_harness::Error> {
+        use itertools::Itertools as _;
+        use serde::de::Deserialize as _;
+
         let data = std::str::from_utf8(data).map_err(toml_test_harness::Error::new)?;
-        let document = data
-            .parse::<toml::Table>()
+        let (table, errors) = toml::de::DeTable::parse_recoverable(data);
+        if !errors.is_empty() {
+            let errors = errors.into_iter().join("\n---\n");
+            let error = toml_test_harness::Error::new(errors);
+            return Err(error);
+        }
+        let document = toml::Table::deserialize(toml::de::Deserializer::from(table))
             .map_err(toml_test_harness::Error::new)?;
         let value = toml::Value::Table(document);
         value_to_decoded(&value)

crates/toml/tests/decoder.rs

@@ -3,3 +3,10 @@ TOML parse error at line 5, column 2
 5 | [a.c]
   |  ^
 cannot extend value of type array with a dotted key
+
+---
+TOML parse error at line 5, column 2
+  |
+5 | [a.c]
+  |  ^
+cannot extend value of type array with a dotted key

crates/toml/tests/snapshots/invalid/array/extending-table.stderr

@@ -3,3 +3,10 @@ TOML parse error at line 1, column 15
 1 | wrong = [ 1 2 3 ]
   |               ^
 missing comma between array elements, expected `,`
+
+---
+TOML parse error at line 1, column 11
+  |
+1 | wrong = [ 1 2 3 ]
+  |           ^^^
+string values must be quoted, expected literal string

crates/toml/tests/snapshots/invalid/array/missing-separator-02.stderr

@@ -3,3 +3,17 @@ TOML parse error at line 1, column 25
 1 | no-close-4 = [{ key = 42
   |                         ^
 newlines are unsupported in inline tables, expected nothing
+
+---
+TOML parse error at line 1, column 26
+  |
+1 | no-close-4 = [{ key = 42
+  |                          ^
+unclosed inline table, expected `}`
+
+---
+TOML parse error at line 1, column 25
+  |
+1 | no-close-4 = [{ key = 42
+  |                         ^
+unclosed array, expected `]`

crates/toml/tests/snapshots/invalid/array/no-close-04.stderr

@@ -3,3 +3,17 @@ TOML parse error at line 1, column 26
 1 | no-close-6 = [{ key = 42 #}]
   |                          ^^^
 comments are unsupported in inline tables, expected nothing
+
+---
+TOML parse error at line 1, column 30
+  |
+1 | no-close-6 = [{ key = 42 #}]
+  |                              ^
+unclosed inline table, expected `}`
+
+---
+TOML parse error at line 1, column 25
+  |
+1 | no-close-6 = [{ key = 42 #}]
+  |                         ^
+unclosed array, expected `]`

crates/toml/tests/snapshots/invalid/array/no-close-06.stderr

@@ -3,3 +3,17 @@ TOML parse error at line 1, column 25
 1 | no-close-4 = [{ key = 42
   |                         ^
 newlines are unsupported in inline tables, expected nothing
+
+---
+TOML parse error at line 1, column 26
+  |
+1 | no-close-4 = [{ key = 42
+  |                          ^
+unclosed inline table, expected `}`
+
+---
+TOML parse error at line 1, column 25
+  |
+1 | no-close-4 = [{ key = 42
+  |                         ^
+unclosed array, expected `]`