CHANGELOG.md

Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

Unreleased

Added

• select! and select_ref! now support cfg attributes.

Removed

Changed

Fixed

[0.12.0] - 2025-12-15

Added

• MapExtra::emit, which allows emitting secondary errors during mapping operations
• InputRef::emit, which allows emitting secondary errors within custom parsers
• labelled_with, which avoids the need to implement Clone for labels
• Input::split_token_span, a convenience function for splitting (Token, Span) inputs so that chumsky can understand them
• Input::split_spanned, which does the same as above, but for implementors of WrappingSpan
• spanned, a combinator which automatically annotates a parser output with a span
• Experimental:
  • IterParser::parse_iter, a way to turn an IterParser (like x.repeated()) into an iterator
  • Parser::debug, which provides access to various parser debugging utilities.

Changed

• Made nested_in more flexible by allowing it to map between different input types instead of requiring the same input as the outer parser

Fixed

• A prioritisation bug with nested_in

[0.11.2] - 2025-11-05

Added

• Implement Default, PartialOrd, and Ord for SimpleSpan
• Implement PartialOrd and Ord for Rich

[0.11.1] - 2025-09-12

Fixed

• Patched compilation error that only appeared in release builds

[0.11.0] - 2025-09-11

Added

• The set(...) combinator, which may be used to conveniently parse a set of patterns, in any order
• Support for non-associative infix operators are now supported by the .pratt(...) combinator
• Parser::try_foldl, allowing folding operations to short-circuit in a manner similar to Parser::try_map
• Parser::contextual, which allows a parser to be disabled or enabled in a context-sensitive manner
• Implemented ValueInput for IterInput, which was previously missing
• More types that implement the State trait:
  • RollbackState, which reverts parser state when a parser rewinds and may be used to, for example, count the number of times a pattern appears in the input
  • TruncateState, which truncates a vector when a parser rewinds, and may be used to implement an arena allocator for AST nodes
• Implemented IterParser for a.then(b) when both a and b are both IterParsers that produce the same output type

Changed

• Made lifetime bounds on recursive and ParserExtra more permissive
• Improved support for grapheme parsing
• Text parsers now report labels
• Parser::filter now generates a DefaultExpected::SomethingElse label instead of nothing (this can be overridden with the .labelled(...) function)
• Improved areas of documentation
• Make whitespace parsers reject codepoints that are vulnerable to CVE-2021-42574
• Maybe the select! parser more permissive, accepting any implementor of Input instead of requiring ValueInput too

Fixed

• Many minor incorrect debug-only sanity checks have been fixed
• Many minor span and error prioritisation behavioural problems have been fixed (most notably, Parser::try_map)
• The .rewind() parser no longer rewinds any secondary error that were encountered
• Accidental text::ascii::keyword lifetime regression

[0.10.1] - 2025-04-13

Added

• Implemented Container for VecDeque
• New section covering recursion in the guide

Changed

• Boxed types now have a default type parameter of extra::Default, like Parser and IterParser
• The tutorial has been updated for 0.10 and has been moved to the guide

Fixed

• Nonsense spans occasionally generated for non-existent tokens
• Improved docs have been added for several items
• Many minor documentation issues have been fixed

[0.10.0] - 2025-03-22

Note: version 0.10 is a from-scratch rewrite of chumsky with innumerable small changes. To avoid this changelog being longer than the compiled works of Douglas Adams, the following is a high-level overview of the major feature additions and does not include small details.

Added

• Support for zero-copy parsing (i.e: parser outputs that hold references to the parser input)
• Support for parsing nested inputs like token trees
• Support for parsing context-sensitive grammars such as Python-style indentation, Rust-style raw strings, and much more
• Support for parsing by graphemes as well as unicode codepoints
• Support for caching parsers independent of the lifetime of the parser
• A new trait, IterParser, that allows expressing parsers that generate many outputs
• Added the ability to collect iterable parsers into fixed-size arrays, along with a plethora of other container types
• Support for manipulating shared state during parsing, elegantly allowing support for arena allocators, cstrees, interners, and much more
• Support for a vast array of new input types: slices, strings, arrays, impl Readers, iterators, etc.
• Experimental support for memoization, allowing chumsky to parse left-recursive grammars and reducing the computational complexity of parsing certain grammars
• An extension API, allowing third-party crates to extend chumsky's capabilities and introduce new combinators
• A pratt parser combinator, allowing for conveniently and simply creating expression parsers with precise operator precedence
• A regex combinator, allowing the parsing of terms based on a specific regex pattern
• Properly differentiated ASCII and Unicode text parsers

Removed

• Parser::then_with has been removed in favour of the new context-sensitive combinators

Changed

• Performance has radically improved
• Error generation and handling is now significantly more flexible

[0.9.2] - 2023-03-02

Fixed

• Properly fixed skip_then_retry_until regression

[0.9.1] - 2023-03-02

Fixed

• Regression in skip_then_retry_until recovery strategy

[0.9.0] - 2023-02-07

Added

• A spill-stack feature that uses stacker to avoid stack overflow errors for deeply recursive parsers
• The ability to access the token span when using select! like select! { |span| Token::Num(x) => (x, span) }
• Added a skip_parser recovery strategy that allows you to implement your own recovery strategies in terms of other parsers. For example, .recover_with(skip_parser(take_until(just(';')))) skips tokens until after the next semicolon
• A not combinator that consumes a single token if it is not the start of a given pattern. For example, just("\\n").or(just('"')).not() matches any char that is not either the final quote of a string, and is not the start of a newline escape sequence
• A semantic_indentation parser for parsing indentation-sensitive languages. Note that this is likely to be deprecated/removed in the future in favour of a more powerful solution
• #[must_use] attribute for parsers to ensure that they're not accidentally created without being used
• Option<Vec<T>> and Vec<Option<T>> now implement Chain<T> and Option<String> implements Chain<char>
• choice now supports both arrays and vectors of parsers in addition to tuples
• The Simple error type now implements Eq

Changed

• text::whitespace returns a Repeated instead of an impl Parser, allowing you to call methods like at_least and exactly on it.
• Improved no_std support
• Improved examples and documentation
• Use zero-width spans for EoI by default
• Don't allow defining a recursive parser more than once
• Various minor bug fixes
• Improved Display implementations for various built-in error types and SimpleReason
• Use an OrderedContainer trait to avoid unexpected behaviour for unordered containers in combination with just

Fixed

• Made several parsers (todo, unwrapped, etc.) more useful by reporting the parser's location on panic
• Boxing a parser that is already boxed just gives you the original parser to avoid double indirection
• Improved compilation speeds

[0.8.0] - 2022-02-07

Added

• then_with combinator to allow limited support for parsing nested patterns
• impl From<&[T; N]> for Stream
• SkipUntil/SkipThenRetryUntil::skip_start/consume_end for more precise control over skip-based recovery

Changed

• Allowed Validate to map the output type
• Switched to zero-size End Of Input spans for default implementations of Stream
• Made delimited_by take combinators instead of specific tokens
• Minor optimisations
• Documentation improvements

Fixed

• Compilation error with --no-default-features
• Made default behaviour of skip_until more sensible

[0.7.0] - 2021-12-16

Added

• A new tutorial to help new users

• select macro, a wrapper over filter_map that makes extracting data from specific tokens easy

• choice parser, a better alternative to long or chains (which sometimes have poor compilation performance)

• todo parser, that panics when used (but not when created) (akin to Rust's todo! macro, but for parsers)

• keyword parser, that parses exact identifiers

• from_str combinator to allow converting a pattern to a value inline, using std::str::FromStr

• unwrapped combinator, to automatically unwrap an output value inline

• rewind combinator, that allows reverting the input stream on success. It's most useful when requiring that a pattern is followed by some terminating pattern without the first parser greedily consuming it

• map_err_with_span combinator, to allow fetching the span of the input that was parsed by a parser before an error was encountered

• or_else combinator, to allow processing and potentially recovering from a parser error

• SeparatedBy::at_most to require that a separated pattern appear at most a specific number of times

• SeparatedBy::exactly to require that a separated pattern be repeated exactly a specific number of times

• Repeated::exactly to require that a pattern be repeated exactly a specific number of times

• More trait implementations for various things, making the crate more useful

Changed

• Made just, one_of, and none_of significant more useful. They can now accept strings, arrays, slices, vectors, sets, or just single tokens as before
• Added the return type of each parser to its documentation
• More explicit documentation of parser behaviour
• More doc examples
• Deprecated seq (just has been generalised and can now be used to parse specific input sequences)
• Sealed the Character trait so that future changes are not breaking
• Sealed the Chain trait and made it more powerful
• Moved trait constraints on Parser to where clauses for improved readability

Fixed

• Fixed a subtle bug that allowed separated_by to parse an extra trailing separator when it shouldn't
• Filled a 'hole' in the Error trait's API that conflated a lack of expected tokens with expectation of end of input
• Made recursive parsers use weak reference-counting to avoid memory leaks

[0.6.0] - 2021-11-22

Added

• skip_until error recovery strategy
• SeparatedBy::at_least and SeparatedBy::at_most for parsing a specific number of separated items
• Parser::validate for integrated AST validation
• Recursive::declare and Recursive::define for more precise control over recursive declarations

Changed

• Improved separated_by error messages
• Improved documentation
• Hid a new (probably) unused implementation details

[0.5.0] - 2021-10-30

Added

• take_until primitive

Changed

• Added span to fallback output function in nested_delimiters

[0.4.0] - 2021-10-28

Added

• Support for LL(k) parsing
• Custom error recovery strategies
• Debug mode
• Nested input flattening

Changed

• Radically improved error quality