Chevrotain

11.1.1 (1-24-2026)

Dependencies Bumps

update dependency lodash-es to v4.17.23
To address CVE: CVE-2025-13465
There were no usages of _.omit or _.unset in the published codebase, (only in test files) So this update should have no functional impact, instead it is meant to address security scanners alerts.

11.1.0 (1-4-2026)

Minor Changes

Support RegExp Lookbehind assertions
- Thanks to @luiz290788 👍

Bug Fixes

Support "Loading ECMAScript modules using require()" of latest nodejs versions
- Chevrotain is still officially ESM only, but this minimal metadata fix may allow some CJS in modern nodejs versions to load chevrotain using CJS require().

11.0.3 (8-15-2023)

Bug Fixes

fix: columns position incorrect after lexer recovery

11.0.2 (8-3-2023)

Bug Fixes

fix: missing source maps and *.ts sources

11.0.1 (7-18-2023)

Bug Fixes

fix: add types to package.json exports
- Thanks to @msujew 👍

11.0.0 (7-11-2023)

Bug Fixes

fix: direct eval() causing warning with esbuild/rollup

10.5.0 (3-11-2023)

Minor Changes

feat: add context argument to recoveryValueFunc
- Thanks to @msujew 👍

10.4.2 (11-21-2022)

Bug Fixes

chore: add types at package.json exports
- Thanks to @msujew 👍

10.4.1 (11-4-2022)

Bug Fixes

fix: missing call to lookahead initialization for experimental lookahead plugins
- Thanks to @msujew 👍

Documentation

docs: fix broken links to protected props

10.4.0 (10-23-2022)

Minor Changes

feat: support pluggable lookahead strategy
- experimental API subject to potential changes...
- Thanks to @msujew 👍

Documentation

docs: IRecognitionException should extend 'Error'
- Thanks to @benhohner 👍

10.3.0 (8-21-2022)

Minor Changes

Removed validating of redundant methods from validateVisitor()

Bug Fixes

runtime exception: Class constructor GAstVisitor cannot be invoked without 'new'

10.2.0 (8-19-2022)

10.1.2 (3-6-2022)

Bug Fixes

missing *.ts source referenced by source maps in sub-packages

Documentation

docs(api.d.ts): add generics for getBaseCstVisitorConstructor functions
- Thanks to @jackhenry 👍

10.1.1 (2-15-2022)

Patch release as a workaround for release process issues...

10.1.0 (2-15-2022)

Minor Changes

customizing automatic token deletion recovery by exposing canRecoverWithSingleTokenDeletion API
- Thanks to @medihack 👍

Bug Fixes

Wrong CST d.ts type generation with same label for different alternatives
- Thanks to @medihack 👍
Recovery Re-Sync logic ignores Token Categories
- Thanks to @medihack 👍

Documentation

various fixes to broken links in docs
- Thanks to @kevinkhill 👍
Update the "where used" list
additional description on token location attributes
- Thanks to @NaridaL 👍

10.0.0 (1-17-2022)

Minor Changes

Generating TypeScript Signatures(d.ts) for CST constructs.
- See relevant documentation
- Thanks to @mbett7 👍
refactor(utils): replace internal utils with lodash
- This adds a new 3rd party dependency (lodash).
- This was done to reduce the amount of code being maintained, but at the cost of increased bundle size, for example: chevrotain.min.js is now 189kb instead of 156kb.

Bug Fixes

CST naming conflicts with built-in Object prototype props

9.1.0 (10-9-2021)

Minor Changes

Support multiple longer_alt tokens
- Thanks to @msujew 👍

9.0.2 (6-13-2021)

Bug Fixes

esm bundle: the export name "__esModule" is reserved and cannot be used

9.0.1 (3-29-2021)

Bug Fixes

fix: missing d.ts definitions in npm package

9.0.0 (3-21-2021)

Bug Fixes

fix: missing "./lib_esm/api_esm.mjs" file in npm package

8.0.1 (2-28-2021)

Bug Fixes

fix: resolve multiple issues with bundled artifacts

8.0.0 (2-28-202)

7.1.2 (2-23-2021)

Patch release after migration to new github org with updated metadata in package.json

7.1.1 (2-5-2021)

Minor Changes

fix: add missing members to parser exception type declarations
- Thanks to @mbett7 :thumbsup
fix: update type declaration for CstChildrenDictionary
- Thanks to @raineszm :thumbsup

7.1.0 (1-2-2021)

Minor Changes

feat: remove constraints on rules and token names
- Thanks to @jlguenego :thumbsup
Add generics to getBaseCSTVisitorConstructor
- Thanks to @ryanleecode :thumbsup

7.0.3 (10-30-2020)

Bug Fixes

Runtime errors after Webpack minification.

7.0.2 (9-4-2020)

Bug Fixes

Empty Alternative inside Nested Repetitions causes infinite loops on Parser initialization.

7.0.0 (4-18-2020)

Minor Changes

Improved Type Signature for 'OR' method
- Thanks to @OmarTawfik :thumbsup
Include source maps and original *.ts sources in npm package

6.4.0 (9-15-2019)

Bug Fixes

Unexpected Side Effects When backtracking in a CstParser

6.3.1 (9-10-2019)

Bug Fixes

Runtime Error thrown when trying to build an Early Exit Parsing Error with maxLookahead 1

6.3.0 (9-8-2019)

Documentation

Cold Start Performance Guide
Deprecate: "Terminal Token Name Not Found" Error
Update Performance Guide
Incorrect Perf Docs
Several TypeScript API fixes for IToken and TokenType
- 1
- 2
- Thanks to @HoldYourWaffle :thumbsup

Dev-Ops

Integrate Algolia Search in the docs website

6.2.0 (8-30-2019)

Minor Changes

Improved handling of alternation ambiguities

Documentation

Documentation for ambiguous alternatives
Several TypeScript API fixes for CustomPatternMatcherFunc
- 1
- 2
- Thanks to @HoldYourWaffle :thumbsup

6.1.0 (8-25-2019)

Minor Changes

Improve Complex Lexers initialization time.

Performance

A resolved performance related bug and a couple of new micro optimizations have produced minor performance improvements in the JSON(5%) and CSS(15%) benchmarks.

Dev-Ops

Create Cold Start Performance benchmark.

6.0.0 (8-20-2019)

Major Changes

Remove usage of Function.prototype.toString().
- Means no more bundling/minification/transpiling issues! with WebPack/Babel/UglifyJS/other...
- Provides a ~20% performance boost to most parsers initialization time.
- These improved analysis capabilities will also enable multiple new features in future versions.
- Thanks to @EqualMa for inspiration & proof of concept :thumbsup

Minor Changes

Parsing Exceptions should be declared as classes.

5.0.0 (8-1-2019)

Minor Changes

Detect missing "performSelfAnalysis" during a parser's input setter.
Provide an ES6 build.
- Thanks to @EqualMa :thumbsup
Restructure api.ts to be ESM compatible.
- Thanks to @EqualMa :thumbsup

4.8.1 (6-21-2019)

Bug Fixes

Resolved edge case in repetition error recovery which may cause "Maximum call stack size exceeded".

4.8.0 (6-14-2019)

Minor Changes

Custom Token Patterns and "Custom Payloads".

4.6.0 (6-1-2019)

Minor Changes

Expose two base Parser classes: CstParser and EmbeddedActionsParser.

4.5.0 (5-25-2019)

Minor Changes

Consider Token Categories in Lookahead Functions Calculation.

4.4.0 (5-24-2019)

Minor Changes

Better handling of infinite loops in repetitions.

4.3.3 (4-12-2019)

Bug Fixes

Performance regressions in Chrome Beta (74)

4.3.2 (4-2-2019)

Bug Fixes

Failure Lexing RegExp patterns starting with empty or "fully optional" groups.
- Thanks to @jmrog :thumbsup

4.3.0 (3-16-2019)

Minor Changes

Updated regexp-to-ast to version 0.4.0.
- This should provide a performance boost to the initialization time of large lexers.
- Thanks to @morwen :thumbsup

Bug Fixes

Fix broken link to docs in lexer disallowed anchors error message.
- Thanks @triplepointfive :thumbsup

4.2.0 (1-26-2019)

Minor Changes

Support Custom Lexer Error Messages Thanks @morwen!

Bug Fixes

Error when building a noAltException with maxLookahead === 1.

4.1.1 (12-14-2018)

Bug Fixes

Alternations ambiguity may not be detected when short repetitions.

4.1.0 (9-28-2018)

Minor Changes

Runtime check for removed Token vector argument in Parser constructor.

4.0.0 (9-26-2018)

Major Changes

Concrete Syntax Tree creation is now enabled by default.

Minor Changes

The Parser's constructor no longer accepts a Token vector as the first argument.
Runtime infinite loop detection in iterations.
Small (~5-10%) performance improvements and optimizations.
- Use ES6 Maps(if available) for faster lookahead functions caching.
- Remove automatic collection of return values for iterations.

Bug Fixes

Stack overflow during grammar analysis..

3.7.3 (7-21-2018)

Bug Fixes

CST - Labels of nonTerminals are lost during error recovery.

3.7.2 (7-19-2018)

Bug Fixes

Performance Regressions under Chrome Canary 69.

3.7.1 (7-12-2018)

Bug Fixes

Potential Very Slow Lexer Initialization.

3.7.0 (6-27-2018)

Minor Changes

Remove global cache (state) and use instance level cache instead.

3.6.1 (6-21-2018)

Bug Fixes

Runtime exception when checking custom patterns line break issues.

3.5.0 (6-10-2018)

Minor Changes

PerformSelfAnalysis can be an instance method..
Previous Token Information on Parser Runtime Errors..
Updated regexp-to-ast to 0.3.3.
Lexer Validations now use regexp-to-ast library when appropriate.

3.4.0 (6-6-2018)

Minor Changes

Detect grammars with none unique names.
Better error message for: "Terminal Token name not found".
Updated regexp-to-ast to 0.2.4.

3.3.0 (5-20-2018)

Documentation

Define APIs separately from the source code.

3.2.0 (4-24-2018)

Documentation

New documentation website generated using vuepress.

3.1.0 (4-13-2018)

Major Changes

Lexer optimizations using the next charCode in the remaining text.

3.0.0 (2-23-2018)

Minor Changes

The CST creation no longer relies on "new Function()" calls and can thus be used in environments with Content Security Policy enabled.

2.0.0 (2-11-2018)

Major Changes

Support custom user defined declarative APIs

Bug Fixes

Added missing link to deprecated TokenType parent property error message.

1.0.1 (12-27-2017)

Bug Fixes

Parser exceptions will now reference the new docs page.

1.0.0 (12-8-2017)

Bug Fixes

Missing token location in EarlyExitException if token is EOF.

0.34.0 (10-15-2017)

Minor Changes

Rework syntax diagrams creation for ease of use and simplicity.

0.33.0 (10-2-2017)

Breaking Changes

Removed "extendToken" and "NEXT*TOKEN" deprecated APIs. Use createToken and LA(1) instead.

Minor Changes

Tiny performance improvements and optimizations.
- 1
- 2
- 3

0.32.0 (7-6-2017)

Major Changes

Lexer Performance oriented release. 10%+ performance boost measured under V8.

0.31.0 (7-1-2017)

Breaking Changes

Token patterns which may include line terminators must be explicitly flagged with the "line_breaks" property.

Major Changes

Support for user defined line terminators.

0.30.0 (6-23-2017)

Minor Changes

Validate that user Token Patterns cannot match an empty string.

0.29.0 (6-13-2017)

Breaking Changes

Default maxLookahead changed to 4
- Originally the default maxLookahead was 5, This could cause very slow parser initialization under certain edge case during ambiguity detection, however the vast majority of grammars do not require five tokens of lookahead. A smaller default avoids these potential slow downs while still allows overriding in unique cases which require a large lookahead.

0.28.3 (5-1-2017)

Bug Fixes

Diagrams drawing bug when using custom Token patterns.

0.28.2 (4-28-2017)

Documentation

Ensure chevrotain.d.ts is compatiable with noImplicitAny.

0.28.1 (4-18-2017)

Minor Changes

Major performance boost for CST Creation.
- 50% speed boost measured on V8 when CST output is enabled.

0.28.0 (4-16-2017)

Major Changes

Concrete Syntax Tree / Semantic Actions Visitor.

Bug Fixes

Definitions: Chevrotain don't support literal string as Token PATTERN in TypeScript.

0.27.3 (3-31-2017)

Minor Changes

Support MultiMode Lexer definitions in Parser Constructor.

0.27.1 (3-29-2017)

Minor Changes

Refactor Lexer for minor performance boost.

Bug Fixes

Certain RegExp meta characters won't be handled correctly in small RegExps.

0.26.0 (3-26-2017)

Minor Changes

Detection of infinite loops caused by grammars with "empty" repetitions.
- Thanks @kdex!

0.25.1 (3-21-2017)

Bug Fixes

Fix Performance regression in Regular Tokens 0.25.0.

0.25.0 (3-19-2017)

Major Changes

Use RegExp sticky flag for lexer performance boost.
- Up to 30% Lexer performance boost measured.

Bug Fixes

0.24.0: Regression: Terminal token name: {name} not found.

0.24.0 (3-17-2017)

Breaking Changes

DSL Methods Improved optional arguments syntax.

Major Changes

Automatic creation of a Concrete Syntax Tree.
- See Relevant Docs.

0.23.0 (2-3-2017)

Major Changes

Custom Token Patterns to Support Lexer Context.

Documentation

Example of lexing python style indentation.

0.20.0 (12-11-2016)

Breaking Changes

More Functional Parsing DSL API.
- This change broke a couple of APIS:
  - "OPTION" now returns the value of the inner grammar implementation or undefined otherwise instead of a boolean.
  - The "*_SEP" methods now return an object made up of two arrays, separators and values instead of a single array of separators.

0.17.1 (10-12-2016)

Bug Fixes

Lexer "Groups" state persists between different inputs tokenization.

Minor Changes

Parsers without error recovery should fail faster on invalid inputs.

0.16.1 (9-28-2016)

Minor Changes

Simple Lazy Tokens should support Token inheritance.

0.16.0 (9-24-2016)

Breaking Changes

The chevrotain TypeScript definitions file is now only compatible with TypeScript 2.0 and later versions. For older versions of TypeScript use Chevrotain versions <= 0.15.0.

0.15.0 (9-23-2016)

Major Changes

Performance Improvements: Lookahead functions.
Performance: SimpleLazyTokens.
"Smart" Map based lookahead for K = 1 with Token inheritance.

This release is focused on performance improvements, with ~20% boost on V8 and potentially ~100% (double) performance on SpiderMonkey (FireFox 49).

To enjoy the maximum performance boost the new SimpleLazyTokens should be used.

Breaking Changes

Certain advanced uses cases of dynamically defined Tokens Will break if some of new lookahead optimizations are enabled.

To resolve this a new property dynamicTokensEnabled has been defined on the IParserConfig interface. This configuration property is disabled by default, but can be enabled to support the use case of dynamically defined tokens. See the dynamically defined Tokens example for details.

0.14.0 (9-3-2016)

Breaking Changes

OR DSL method Syntax should be more consistent.

Minor Changes

Performance Optimizations for 0.14.0 release.

0.13.4 (9-1-2016)

Minor Changes

Change NPMCDN links to use UNPKG domain name.

0.13.3 (8-28-2016)

Bug Fixes

Slow Parser Initialization.

0.13.2 (8-23-2016)

Bug Fixes

Diagrams with nodejs fail on instanceof check.

0.13.1 (8-15-2016)

Major Changes

This Release includes a new performance feature called "Lazy Tokens". These tokens contain less actual state and defer the calculation of their properties until needed. Considering most of the time this information is never needed (full position information) the overall speed boost can be as much as 10-25% (depending on the grammar used).

See "2. Use Lazy Tokens" for more details.

0.13.0 (8-6-2016)

Major Changes

0.13.0 Performance Optimizations.
Performance FAQ section docs.

This release includes major performance optimizations and guidelines. Anywhere from 20% to 100% was measured (on V8) depending on the grammar used. Please read the Performance FAQ section, as much of the performance gain is achieved by changing the way a Chevrotain parser is initialized which will require code changes (not mandatory) in user's code.

0.12.1 (8-3-2016)

Bug Fixes

Diagrams do not work with custom lexers.

Documentation

Improve support for running minified in the browser.

0.12.0 (7-21-2016)

Breaking Changes

Removed Bower support.

Bug Fixes

Documentation

Example using parametrized sub-rules.

0.11.4 (7-16-2016)

Fixes issue with previous release automation.

0.11.3 (7-16-2016)

Bug Fixes

AmbiguousAlternatives error's <occurence> property was always undefined.

Quality

Use SauceLabs for browser matrix testing

0.11.2 (7-5-2016)

Minor Changes

Documentation

Dynamically defined Tokens example.

0.11.1 (6-16-2016)

Minor Changes

extendToken should create constructor functions with meaningful names

0.11.0 (6-7-2016)

Minor version release as the previous version included a breaking change in a patch version.

Minor Changes

Better runtime checks for Invalid Lexer definitions.

0.10.2 (6-6-2016)

Breaking Changes

MultiMode Lexer defaultMode should not be implicitly defined.

Documentation

XML grammar example.

0.10.1 (5-30-2016)

Fixes issue with previous release automation.

0.10.0 (5-29-2016)

Major Changes

Breaking Changes

IsNextRule method was removed from the Parser class. It's functionality is no longer needed as usage of predicates / gates no longer requires manually (re)implementing the lookahead function.
DSL methods with separators should not support predicates.
Move all "parse time" grammar validations to the initialization phase (grammar construction).

Documentation

Example implementing syntactic & semantic content assist.

0.9.0 (4-29-2016)

Major Changes

Support LL(k) grammars.

0.8.1 (4-11-2016)

Minor Changes

Avoid rebuilding the GAST on parser construction when using RULE_OVERRIDE.

Bug Fixes

GAST Production cache does not take into account grammar inheritance

0.8.0 (4-8-2016)

Breaking Changes

Some breaking API changes in this version. Most have the changes have been to optional arguments, so not many changes will be needed (if at all) for most users.

Use a config object for RULE DSL method.
The RULE method's optional third and fourth parameters have been been replaced with a single configuration object of the type IRuleConfig. Therefore any RULE invocation with more than two arguments must be refactored to the new form. For example:
```
    // old deprecated form
    this.RULE("createStmt", function(){ /* ... */}, function(){ return 666 })

    // new form
    this.RULE("createStmt", function(){ /* ... */}, {recoveryValueFunc: function(){ return 666 }})
```

Remove RULE_NO_RESYNC DSL method.

The RULE_NO_RESYNC convenience method has been removed. All usages of it must be replaced with an equivalent RULE call using the IRuleConfig resyncEnabled property.

For example:

// old deprecated form
this.RULE_NO_RESYNC("createStmt", function () {
  /* ... */
});

// new form
this.RULE(
  "createStmt",
  function () {
    /* ... */
  },
  { resyncEnabled: false },
);

Parser Configuration should be done using a "Config" Object instead of constructor parameters.

Error Recovery / Fault Tolerance abilities should be disabled by default.

The Parser constructors's third (optional) parameter has been been replaced with a single configuration object of the type IParserConfig Therefore any Base Parser super invocation which uses the optional parameter must be updated. Additionally The Error recovery functionality is now disabled by default, it can be enabled via the parser's configuration. For example:

// old deprecated form
function JsonParser(input) {
  // The third argument was used to enable/disable error recovery
  // and was **true** by default.
  Parser.call(this, input, true);
}

// new form
function JsonParser(input) {
  // invoke super constructor
  Parser.call(this, input, allTokens, {
    // by default the error recovery flag is **false**
    // use recoveryEnabled flag in the IParserConfig object to enable enable it.
    recoveryEnabled: true,
  });
}

0.7.2 (4-7-2016)

Minor Changes

Support Overriding Rule implementations in inheriting grammars.

Documentation

Bring order to the chaos of the examples folder.

Lexer multi "modes" support.

0.6.3 (3-28-2016)

Minor Changes

Re-synced tokens should be reported to the user.

0.6.2 (3-25-2016)

Bug Fixes

LexerDefinitionErrorType enum was not exported as part of the public API.

0.6.1 (3-25-2016)

Bug Fixes

ParserDefinitionError enum was not exported.

0.6.0 (3-20-2016)

Breaking Changes

Reorganized projected structure to be consistent and use "lib" folder Chevrotain's aggregated artifacts are now located under the lib folder instead of the bin folder in the npm package or the release folder in the bower package.
This means that references to "bower_components/chevrotain/release/..." or "node_modules/chevrotain/bin/..." Will have to be replaced with references to ".../lib/...".
For example - modified diagrams.html
Note that no changes are needed for standard consumption of chevrotain under node.js (require('chevrotain')).

Bug Fixes

Diagrams - Fixed global references to permit UMD loading.

0.5.23 (3-17-2016)

Bug Fixes

Syntax Diagrams usage highlights issues.

Diagrams template resources were not fully included in bower "package".

Older Releases changelog is available on Github Releases.