feat(parser): add `mutate_tokens` Cargo feature by overlookmotel · Pull Request #19853 · oxc-project/oxc

overlookmotel · 2026-02-28T15:39:29Z

#19852 made Tokens impossible to mutate outside of the lexer.

Add an escape hatch to provide methods to mutate them, for use in ESTree conversion, behind a mutate_tokens Cargo feature.

Also add a Token::set_span method, to complement the other setter methods.

overlookmotel · 2026-02-28T15:40:11Z

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codspeed-hq · 2026-02-28T15:46:20Z

Merging this PR will not alter performance

✅ 52 untouched benchmarks
⏩ 3 skipped benchmarks¹

_{Comparing om/02-24-feat_parser_add_mutate_tokens_cargo_feature (f78e6df) with main (c1bfdcf)²}

3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩
No successful run was found on main (29a5a68) during the generation of this report, so c1bfdcf was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

Copilot

Pull request overview

This PR adds a mutate_tokens Cargo feature to oxc_parser as an escape hatch, enabling external mutation of Token fields that were previously locked down inside the lexer module (as part of PR #19852). It exposes Token::set_kind and a newly added Token::set_span as pub (instead of pub(super)) when the feature is enabled, intended for use in ESTree tokens conversion.

Changes:

Introduces mutate_tokens Cargo feature in Cargo.toml with a descriptive comment about its restricted usage
Adds new Token::set_span method (and helper set_span_impl) that sets both start and end in one call, gated behind the feature
Refactors Token::set_kind to use the same dual #[cfg] / #[cfg(not)] pattern as set_span, promoting it to pub when the feature is enabled
Updates the token_setters test to use the new set_span method

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
`crates/oxc_parser/Cargo.toml`	Adds the new `mutate_tokens = []` feature with documentation comment
`crates/oxc_parser/src/lexer/token.rs`	Adds `set_span`/`set_span_impl`, refactors `set_kind`, and updates tests to use `set_span`

overlookmotel · 2026-02-28T16:07:47Z

Merge activity

Feb 28, 4:07 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Feb 28, 4:53 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
Feb 28, 5:10 PM UTC: Merged by the Graphite merge queue.

#19852 made `Token`s impossible to mutate outside of the lexer. Add an escape hatch to provide methods to mutate them, for use in ESTree conversion, behind a `mutate_tokens` Cargo feature. Also add a `Token::set_span` method, to complement the other setter methods.

### 🚀 Features - 733d6dc parser: Report error on `infer` outside conditional type (#19879) (camc314) - c2a42f6 allocator: Add `Vec::into_bump_slice_mut` (#19895) (overlookmotel) - ee4982b parser: Add `VARIANTS` const to `Kind` via `fieldless_enum!` macro (#19877) (overlookmotel) - b3dceae data_structures: Add `fieldless_enum!` macro (#19876) (overlookmotel) - 12b841e parser: Make all `Kind::is_*` methods `const` (#19874) (overlookmotel) - 25c2e25 estree/tokens: Add function to update tokens in place (#19856) (overlookmotel) - f78e6df parser: Add `mutate_tokens` Cargo feature (#19853) (overlookmotel) - 5036bb6 parser: Report error on `for await` in static blocks (#19844) (camc314) - 42bd431 parser: Report error for missing initializer in using decl (#19824) (camc314) - a2f58e5 parser: Report error for `implements` clause in non-ts files (#19820) (Cameron) - b25228a estree: Add `IS_COMPACT` const to `Formatter` trait (#19787) (overlookmotel) - e2a1b79 estree: Expose buffer and formatter of serializers (#19773) (overlookmotel) - 4699498 data_structures: Add `CodeBuffer::print_strs_array` (#19760) (overlookmotel) - 233f947 estree: `oxc_estree` crate export config and formatter types (#19724) (overlookmotel) - 5937a32 semantic: Introduce `symbol_declarations` method (#19609) (camc314) - ea6b796 parser: Add `LexerConfig::TOKENS_METHOD_IS_STATIC` const (#19683) (overlookmotel) - 655c38f semantic: Add "did you mean?" suggestions to undefined name errors (#19102) (copilot-swe-agent) - 9e11dc6 parser,estree,coverage: Collect tokens in parser and convert to ESTree format (#19497) (camc314) - c4a3677 parser: Report error for initializer in ambient context (#19187) (camc314) ### 🐛 Bug Fixes - abc7e19 codegen: Improve parenthesised checks when printing types (#19880) (camc314) - 017de5d parser: Update error code for type annotation in `for...in` statement (#19882) (camc314) - 7682e5a linter/plugins: Decode escapes in identifier tokens (#19838) (overlookmotel) - 06767ed estree/tokens: Convert `this` tokens in `TSTypeName` (#19815) (overlookmotel) - ef798af parser: Use TS8037 for satisfies expression in JS files diagnostic (#19819) (camc314) - 98ea5c5 parser: Use TS8016 for type assertions in JS files diagnostic (#19818) (camc314) - 1710f56 codegen: Remove double indentation for enum inside namespace (#19775) (Dunqing) - 9e4995c codegen: Print type annotation on `CatchParameter` (#19790) (camc314) - 297b2bb codegen: Wrap `TSConditionalType` in parens when necessary (#19788) (camc314) - cec7878 codegen: Print `definite` property on AccessorProperty (#19786) (camc314) - 6f395cf codegen: Print `definite` property on PropertyDefinition (#19785) (camc314) - b749373 codegen: Correctly parenthesise TSArrayType (#19784) (camc314) - 876dc1b codegen: Print object property `this` param (#19783) (camc314) - 93bb861 formatter: Trim trailing whitespace before breaking line (#19740) (leaysgur) - ed17bbf codegen: Print `override` keyword for method and property definitions (#19753) (Dunqing) - 6a59a76 parser: Improve error recovery for private identifiers in property names (#19710) (Boshen) - 3b96f41 codegen: Print comments in JSX expression containers and spread attributes (#19701) (Boshen) - f5694ce estree/tokens: Reverse field order of `regex` object in tokens (#19679) (overlookmotel) - b2b7a55 estree/tokens: Generate tokens for files with BOM (#19535) (overlookmotel) - 50a7514 estree: Fix tokens for JSX (#19524) (overlookmotel) - a35063e minifier: Preserve side effects for meta property url reads (#19668) (Boshen) - 8ad3430 semantic/jsdoc: Handle even-numbered backtick sequences in JSDoc parsing (#19664) (Boshen) ### ⚡ Performance - 05ccf9f linter/plugins: Transfer tokens via raw transfer (#19893) (overlookmotel) - c1bfdcf estree/tokens: Preallocate sufficient space for tokens JSON (#19851) (overlookmotel) - 4b0611a estree/tokens: Introduce `ESTreeTokenConfig` trait (#19842) (overlookmotel) - 81bab90 estree/tokens: Do not JSON-encode keyword, punctuator, etc tokens (#19814) (overlookmotel) - 6260ddd estree/tokens: Do not JSON-encode `this` identifiers (#19813) (overlookmotel) - b378f4a estree/tokens: Do not JSON-encode JSX identifiers (#19812) (overlookmotel) - 5016d92 estree/tokens: Handle regex tokens separately (#19796) (overlookmotel) - 780a68e estree/tokens: Use strings from AST for identifier tokens (#19744) (overlookmotel) - dc9c2e3 estree: Use `CodeBuffer::print_strs_array` to reduce bounds checks (#19766) (overlookmotel) - 845da35 estree: Use `CodeBuffer::print_indent` (#19727) (overlookmotel) - ec88f6a estree/tokens: Serialize tokens while visiting AST (#19726) (overlookmotel) - bc6507f estree/tokens: Serialize with `ESTree` not `serde` (#19725) (overlookmotel) - ec24859 estree/tokens: Do not branch on presence of override twice (#19721) (overlookmotel) - dac14be estree/tokens: Replace hash map with `Vec` (#19718) (overlookmotel) - b9d2443 estree/tokens: Replace multiple hash sets into a single hash map (#19716) (overlookmotel) - 7233548 parser: Remove branches from `finish_next_inner` (#19695) (overlookmotel) - b5d9845 parser: Remove const generic param from `finish_next_inner` (#19684) (overlookmotel) - 8940f66 estree/tokens: Serialize tokens to compact JSON (#19572) (overlookmotel) - 136e39b parser/tokens: Pre-allocate capacity for tokens (#19543) (overlookmotel) - 6a6513c linter/plugins: Use Oxc tokens in plugins (#19498) (camc314) - b3b2d30 parser: Introduce `ParserConfig` (#19637) (overlookmotel) ### 📚 Documentation - b2b7a64 estree/tokens: Correct comment (#19873) (overlookmotel) - 0399311 estree/tokens: Improve comments (#19836) (overlookmotel) - 1b392de minifier: Add `Function.prototype.toString` assumption (#19758) (sapphi-red) - 75c9cd8 parser: Improve doc comments for `ParserConfig` and `LexerConfig` (#19682) (overlookmotel) - 2fa936f README.md: Map npm package links to npmx.dev (#19666) (Boshen) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

github-actions bot added A-parser Area - Parser C-enhancement Category - New feature or request labels Feb 28, 2026

This was referenced Feb 28, 2026

refactor(parser): Token::set_* method visible only within lexer #19852

Merged

ci(benchmarks): add benchmark for updating tokens for raw transfer #19854

Merged

overlookmotel marked this pull request as ready for review February 28, 2026 15:44

Copilot AI review requested due to automatic review settings February 28, 2026 15:44

Copilot started reviewing on behalf of overlookmotel February 28, 2026 15:44 View session

overlookmotel self-assigned this Feb 28, 2026

overlookmotel added the A-linter-plugins Area - Linter JS plugins label Feb 28, 2026

Copilot AI reviewed Feb 28, 2026

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overlookmotel changed the base branch from om/02-24-refactor_parser_kind_set__method_visible_only_within_lexer to graphite-base/19853 February 28, 2026 16:06

overlookmotel force-pushed the om/02-24-feat_parser_add_mutate_tokens_cargo_feature branch from 358f70b to 9022536 Compare February 28, 2026 16:07

overlookmotel force-pushed the graphite-base/19853 branch from 697c7be to c32a896 Compare February 28, 2026 16:07

overlookmotel changed the base branch from graphite-base/19853 to om/02-24-refactor_parser_kind_set__method_visible_only_within_lexer February 28, 2026 16:07

overlookmotel force-pushed the om/02-24-refactor_parser_kind_set__method_visible_only_within_lexer branch from c32a896 to 834c7d1 Compare February 28, 2026 16:46

overlookmotel force-pushed the om/02-24-feat_parser_add_mutate_tokens_cargo_feature branch from 9022536 to 45f9af2 Compare February 28, 2026 16:46

graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Feb 28, 2026

graphite-app bot force-pushed the om/02-24-refactor_parser_kind_set__method_visible_only_within_lexer branch from 834c7d1 to 29a5a68 Compare February 28, 2026 17:01

graphite-app bot force-pushed the om/02-24-feat_parser_add_mutate_tokens_cargo_feature branch from 45f9af2 to f78e6df Compare February 28, 2026 17:02

Base automatically changed from om/02-24-refactor_parser_kind_set__method_visible_only_within_lexer to main February 28, 2026 17:08

graphite-app bot merged commit f78e6df into main Feb 28, 2026
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graphite-app bot deleted the om/02-24-feat_parser_add_mutate_tokens_cargo_feature branch February 28, 2026 17:10

Boshen mentioned this pull request Mar 2, 2026

release(crates): oxc v0.116.0 #19911

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feat(parser): add `mutate_tokens` Cargo feature#19853

feat(parser): add `mutate_tokens` Cargo feature#19853
graphite-app[bot] merged 1 commit intomainfrom
om/02-24-feat_parser_add_mutate_tokens_cargo_feature

overlookmotel commented Feb 28, 2026 •

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