perf(estree/tokens): do not JSON-encode keyword, punctuator, etc tokens by overlookmotel · Pull Request #19814 · oxc-project/oxc

overlookmotel · 2026-02-27T14:00:47Z

After #19744, #19813, #19812, and #19796, all tokens which require special handling or can contain values which are possibly not JSON-safe are handled separately. So everything remaining (keywords, punctuators etc) are JSON-safe and can be serialized via the optimized serializer introduced for identifiers in #19744.

To reflect that EstreeIdentToken now handles a lot more than identifiers, rename it to EstreeSafeToken, and rename EstreeToken to EstreeUnsafeToken.

Large positive perf impact. +24% on ESTree tokens benchmark.

overlookmotel · 2026-02-27T14:01:15Z

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codspeed-hq · 2026-02-27T14:07:07Z

Merging this PR will improve performance by 24.01%

⚡ 1 improved benchmark
✅ 51 untouched benchmarks
⏩ 3 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
⚡	Simulation	`estree_tokens[checker.ts]`	127.7 ms	102.9 ms	+24.01%

_{Comparing om/02-22-perf_estree_tokens_do_not_json-encode_keyword_punctuator_etc_tokens (7369657) with om/02-22-perf_estree_tokens_do_not_json-encode_this_identifiers (efa2364)}

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. ↩

Copilot

Pull request overview

Optimizes ESTree token JSON serialization by routing JSON-safe tokens (keywords, punctuators, numbers, booleans, null, and most identifiers) through a fast manual serializer, while keeping escape-checked serialization for token values that may contain JSON-unsafe bytes.

Changes:

Introduces EstreeSafeToken (manual JSON assembly) and renames the previous general token type to EstreeUnsafeToken.
Refactors token emission to default to the safe fast-path and adds visitors to ensure string/template/JSXText tokens are emitted via the unsafe path.
Tightens invariants around which token kinds may reach get_token_type (debug assertion) after splitting safe vs unsafe handling.

crates/oxc_estree_tokens/src/lib.rs

overlookmotel · 2026-02-27T18:37:42Z

Merge activity

Feb 27, 6:37 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 27, 6:37 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
Feb 27, 6:49 PM UTC: Merged by the Graphite merge queue.

…ns (#19814) After #19744, #19813, #19812, and #19796, all tokens which require special handling or can contain `value`s which are possibly not JSON-safe are handled separately. So everything remaining (keywords, punctuators etc) are JSON-safe and can be serialized via the optimized serializer introduced for identifiers in #19744. To reflect that `EstreeIdentToken` now handles a lot more than identifiers, rename it to `EstreeSafeToken`, and rename `EstreeToken` to `EstreeUnsafeToken`. Large positive perf impact. +24% on ESTree tokens benchmark.

Remove the `regex` field from `EstreeToken` and serialize regex tokens via their own dedicated type `EstreeRegExpToken`. This removes a branch and logic from `emit_token` which is the path the processes all tokens except identifiers. This PR is actually showing as a small perf degradation (-1% on ESTree tokens benchmark). But it enables a much bigger optimization later on in #19814.

Same as #19744, but for `this` identifiers in TS types. Serialize them using the same optimized `EstreeIdentToken` serializer added in that PR. This isn't a hot path so makes little difference, but it completes the preconditions for the next PR #19814.

### 🚀 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 the C-performance Category - Solution not expected to change functional behavior, only performance label Feb 27, 2026

This was referenced Feb 27, 2026

perf(estree/tokens): handle regex tokens separately #19796

Merged

perf(estree/tokens): do not JSON-encode JSX identifiers #19812

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overlookmotel mentioned this pull request Feb 27, 2026

perf(estree/tokens): do not JSON-encode this identifiers #19813

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overlookmotel mentioned this pull request Feb 27, 2026

fix(estree/tokens): convert this tokens in TSTypeName #19815

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camc314 assigned overlookmotel Feb 27, 2026

overlookmotel marked this pull request as ready for review February 27, 2026 18:24

Copilot AI review requested due to automatic review settings February 27, 2026 18:24

overlookmotel added A-parser Area - Parser A-linter-plugins Area - Linter JS plugins labels Feb 27, 2026

Copilot started reviewing on behalf of overlookmotel February 27, 2026 18:24 View session

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overlookmotel added the 0-merge Merge with Graphite Merge Queue label Feb 27, 2026

graphite-app bot force-pushed the om/02-22-perf_estree_tokens_do_not_json-encode_this_identifiers branch from efa2364 to 6260ddd Compare February 27, 2026 18:40

graphite-app bot force-pushed the om/02-22-perf_estree_tokens_do_not_json-encode_keyword_punctuator_etc_tokens branch from 7369657 to 81bab90 Compare February 27, 2026 18:40

graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Feb 27, 2026

Base automatically changed from om/02-22-perf_estree_tokens_do_not_json-encode_this_identifiers to main February 27, 2026 18:48

graphite-app bot merged commit 81bab90 into main Feb 27, 2026
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graphite-app bot deleted the om/02-22-perf_estree_tokens_do_not_json-encode_keyword_punctuator_etc_tokens branch February 27, 2026 18:49

Boshen mentioned this pull request Mar 2, 2026

release(crates): oxc v0.116.0 #19911

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perf(estree/tokens): do not JSON-encode keyword, punctuator, etc tokens#19814

perf(estree/tokens): do not JSON-encode keyword, punctuator, etc tokens#19814
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om/02-22-perf_estree_tokens_do_not_json-encode_keyword_punctuator_etc_tokens

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Merging this PR will improve performance by 24.01%

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overlookmotel commented Feb 27, 2026 •

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