perf(napi/parser, linter/plugins): simplify branch condition in `deserializeStr` by overlookmotel · Pull Request #21019 · oxc-project/oxc

overlookmotel · 2026-04-03T19:37:43Z

Follow-on after #20834.

Simplify the branch condition in deserializeStr for detemining if can take the fast path of just slicing sourceText. There's no need to check sourceIsAscii, just compare the offset to firstNonAsciiPos (the position in buffer of first non-ASCII byte in source code). When source is 100% ASCII, firstNonAsciiPos = sourceEndPos, so pos < firstNonAsciiPos passes for all positions in source.

The implementation is different for parser and for Oxlint, as the source text sits in a different location in buffer - at the start in parser, at the end in Oxlint - but the principle is the same in both.

Benchmarking showed this speeds up deserializeStr by a small percentage.

overlookmotel · 2026-04-03T19:37:59Z

How to use the Graphite Merge Queue

Add either label to this PR to merge it via the merge queue:

0-merge - adds this PR to the back of the merge queue
hotfix - for urgent changes, fast-track this PR to the front of the merge queue

You must have a Graphite account in order to use the merge queue. Sign up using this link.

_{An organization admin has enabled the Graphite Merge Queue in this repository.} _{Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.}

This stack of pull requests is managed by Graphite. Learn more about stacking.

Copilot

Pull request overview

This PR refines the fast-path condition in deserializeStr to decide when it can safely return a substring slice of sourceText (instead of decoding bytes), by relying solely on firstNonAsciiPos (and sourceStartPos in the oxlint layout) rather than also branching on sourceIsAscii. This aligns with the post-#20834 approach of using an ASCII-prefix boundary to keep the hot path cheap while preserving correctness for mixed-encoding sources.

Changes:

Simplifies the deserializeStr fast-path condition to end <= firstNonAsciiPos (plus pos >= sourceStartPos for oxlint’s buffer layout).
Adjusts initialization of firstNonAsciiPos to be computed as the first non-ASCII byte (or the end of the source region when fully ASCII), with different buffer offsets for parser vs oxlint.
Regenerates all affected JS deserializer outputs.

Reviewed changes

Copilot reviewed 1 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tasks/ast_tools/src/generators/raw_transfer.rs	Updates the generator logic for computing `firstNonAsciiPos` and emitting the simplified fast-path condition in `deserializeStr`.
napi/parser/src-js/generated/deserialize/ts.js	Regenerated parser TS deserializer: removes `sourceIsAscii/sourceEndPos` state and uses `end <= firstNonAsciiPos`.
napi/parser/src-js/generated/deserialize/ts_range.js	Same regeneration for TS+range variant.
napi/parser/src-js/generated/deserialize/ts_range_parent.js	Same regeneration for TS+range+parent variant.
napi/parser/src-js/generated/deserialize/ts_parent.js	Same regeneration for TS+parent variant.
napi/parser/src-js/generated/deserialize/js.js	Regenerated parser JS deserializer: same fast-path simplification.
napi/parser/src-js/generated/deserialize/js_range.js	Same regeneration for JS+range variant.
napi/parser/src-js/generated/deserialize/js_range_parent.js	Same regeneration for JS+range+parent variant.
napi/parser/src-js/generated/deserialize/js_parent.js	Same regeneration for JS+parent variant.
apps/oxlint/src-js/generated/deserialize.js	Regenerated oxlint deserializer: uses absolute `firstNonAsciiPos` and checks `pos >= sourceStartPos && end <= firstNonAsciiPos`.

graphite-app · 2026-04-03T22:03:38Z

Merge activity

Apr 3, 10:03 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
Apr 3, 10:12 PM UTC: Merged by the Graphite merge queue.

…rializeStr` (#21019) Follow-on after #20834. Simplify the branch condition in `deserializeStr` for detemining if can take the fast path of just slicing `sourceText`. There's no need to check `sourceIsAscii`, just compare the offset to `firstNonAsciiPos` (the position in buffer of first non-ASCII byte in source code). When source is 100% ASCII, `firstNonAsciiPos = sourceEndPos`, so `pos < firstNonAsciiPos` passes for all positions in source. The implementation is different for parser and for Oxlint, as the source text sits in a different location in buffer - at the start in parser, at the end in Oxlint - but the principle is the same in both. [Benchmarking](https://github.com/overlookmotel/oxc-raw-str-bench) showed this speeds up `deserializeStr` by a small percentage.

### 🐛 Bug Fixes - fc7f60c allocator: Revert changes to `get_current_chunk_footer_field_offset` (#20964) (overlookmotel) - 31316c8 semantic: Rebind class expressions before identifier checks (#20916) (camc314) ### ⚡ Performance - fb52383 napi/parser, linter/plugins: Clear buffers and source texts earlier (#21025) (overlookmotel) - 3b7dec4 napi/parser, linter/plugins: Use `utf8Slice` for decoding UTF-8 strings (#21022) (overlookmotel) - 012c924 napi/parser, linter/plugins: Speed up decoding strings in raw transfer (#21021) (overlookmotel) - 55e1e9b napi/parser, linter/plugins: Initialize vars as 0 (#21020) (overlookmotel) - c25ef02 napi/parser, linter/plugins: Simplify branch condition in `deserializeStr` (#21019) (overlookmotel) - 9f494c3 napi/parser, linter/plugins: Raw transfer use `String.fromCharCode` in string decoding (#21018) (overlookmotel) - 91cf105 allocator: Increase initial chunk size from 512B to 16KB (#20968) (overlookmotel) - cbc0c21 allocator: Add `#[cold]` to to error handling functions (#20967) (overlookmotel) - 0503a78 napi/parser, linter/plugins: Faster deserialization of `raw` fields (#20923) (overlookmotel) - a24f75e napi/parser: Optimize string deserialization for non-ASCII sources (#20834) (Joshua Tuddenham) ### 📚 Documentation - c78a57a syntax: Fix typo (#21044) (camc314) - f5e228f allocator: Fix typo in comment (#20972) (overlookmotel) - 7159d51 allocator: Improve doc comment examples for `vec2::Vec` (#20969) (overlookmotel) - b1da750 allocator, data_structures: Correct comments (#20966) (overlookmotel) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

# Oxlint ### 💥 BREAKING CHANGES - 22ce6af oxlint/lsp: [**BREAKING**] Show/fix safe suggestions by default (#19816) (Sysix) ### 🚀 Features - 7a7b7b8 oxlint/lsp: Add source.fixAllDangerous.oxc code action kind (#20526) (bab) - 9cfe57e linter/unicorn: Implement prefer-import-meta-properties rule (#20662) (Irfan - ئىرفان) - 1edb391 linter/eslint: Implement `no-restricted-exports` rule (#20592) (Nicolas Le Cam) - 0f12bcd linter/react: Implement `hook-use-state` rule (#20986) (Khaled Labeb) - 1513a9f oxlint/lsp: Show note field for lsp diagnostic (#20983) (Sysix) - 7fdf722 linter/unicorn: Implement `no-useless-iterator-to-array` rule (#20945) (Mikhail Baev) - 39c8f2c linter/jest: Implement padding-around-after-all-blocks (#21034) (Sapphire) - ac39e51 linter/eslint-vitest-plugin: Prefer importing vitest globals (#20960) (Said Atrahouch) - 0b84de1 oxlint: Support allow option for prefer-promise-reject-errors (#20934) (camc314) - 23db851 linter/consistent-return: Move rule from nursery to suspicious (#20920) (camc314) - 9a27e32 linter/no-unnecessary-type-conversion: Move rule from nursery to suspicious (#20919) (camc314) - 1ca7b58 linter/dot-notation: Move rule from nursery to style (#20918) (camc314) - 73ba81a linter/consistent-type-exports: Move rule from nursery to style (#20917) (camc314) - b9199b1 linter/unicorn: Implement switch-case-break-position (#20872) (Mikhail Baev) - 3435ff8 linter: Implements `prefer-snapshot-hint` rule in Jest and Vitest (#20870) (Said Atrahouch) - 98510d2 linter: Implement react/prefer-function-component (#19652) (Connor Shea) - 871f9d9 linter: Implement no-useless-assignment (#15466) (Zhaoting Zhou) - 0f01fbd linter: Implement eslint/object-shorthand (#17688) (yue) ### 🐛 Bug Fixes - dd2df87 npm: Export package.json for oxlint and oxfmt (#20784) (kazuya kawaguchi) - 9bc77dd linter/no-unused-private-class-members: False positive with await expr (#21067) (camc314) - 60a57cd linter/const-comparisons: Detect equality contradictions (#21065) (camc314) - 2bb2be2 linter/no-array-index-key: False positive when index is passed as function argument (#21012) (bab) - 6492953 linter/no-this-in-sfc: Only flag `this` used as member expression object (#20961) (bab) - 9446dcc oxlint/lsp: Skip `node_modules` in oxlint config walker (#21004) (copilot-swe-agent) - af89923 linter/no-namespace: Support glob pattern matching against basename (#21031) (bab) - 64a1a7e oxlint: Don't search for nested config outside base config (#21051) (Sysix) - 3b953bc linter/button-has-type: Ignore `document.createElement` calls (#21008) (Said Atrahouch) - 8c36070 linter/unicorn: Add support for `Array.from()` for `prefer-set-size` rule (#21016) (Mikhail Baev) - c1a48f0 linter: Detect vitest import from vite-plus/test (#20976) (Said Atrahouch) - 5c32fd1 lsp: Prevent corrupted autofix output from overlapping text edits (#19793) (Peter Wagenet) - ca79960 linter/no-array-index-key: Move span to `key` property (#20947) (camc314) - 2098274 linter: Add suggestion for `jest/prefer-equality-matcher` (#20925) (eryue0220) - 6eb77ec linter: Allow default-import barrels in import/named (#20757) (Bazyli Brzóska) - 9c218ef linter/eslint-vitest-plugin: Remove pending fix status for require-local-test-context-for-concurrent-snapshot (#20890) (Said Atrahouch) ### ⚡ Performance - fb52383 napi/parser, linter/plugins: Clear buffers and source texts earlier (#21025) (overlookmotel) - 3b7dec4 napi/parser, linter/plugins: Use `utf8Slice` for decoding UTF-8 strings (#21022) (overlookmotel) - 012c924 napi/parser, linter/plugins: Speed up decoding strings in raw transfer (#21021) (overlookmotel) - 55e1e9b napi/parser, linter/plugins: Initialize vars as 0 (#21020) (overlookmotel) - c25ef02 napi/parser, linter/plugins: Simplify branch condition in `deserializeStr` (#21019) (overlookmotel) - 9f494c3 napi/parser, linter/plugins: Raw transfer use `String.fromCharCode` in string decoding (#21018) (overlookmotel) - 0503a78 napi/parser, linter/plugins: Faster deserialization of `raw` fields (#20923) (overlookmotel) - a24f75e napi/parser: Optimize string deserialization for non-ASCII sources (#20834) (Joshua Tuddenham) ### 📚 Documentation - af72b80 oxlint: Fix typo for --tsconfig (#20889) (leaysgur) - 70c53b1 linter: Highlight that tsconfig is not respected in type aware linting (#20884) (camc314) # Oxfmt ### 🚀 Features - 35cf6e8 oxfmt: Add node version hint for ts config import failures (#21046) (camc314) ### 🐛 Bug Fixes - dd2df87 npm: Export package.json for oxlint and oxfmt (#20784) (kazuya kawaguchi) - 9d45511 oxfmt: Propagate file write errors instead of panicking (#20997) (leaysgur) - 139ddd9 formatter: Handle leading comment after array elision (#20987) (leaysgur) - 4216380 oxfmt: Support `.editorconfig` `tab_width` fallback (#20988) (leaysgur) - d10df39 formatter: Resolve pending space in fits measurer before expanded-mode early exit (#20954) (Dunqing) - f9ef1bd formatter: Avoid breaking after `=>` when arrow body has JSDoc type cast (#20857) (bab) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

github-actions bot added A-linter Area - Linter A-parser Area - Parser A-cli Area - CLI A-ast-tools Area - AST tools A-linter-plugins Area - Linter JS plugins C-performance Category - Solution not expected to change functional behavior, only performance labels Apr 3, 2026

overlookmotel marked this pull request as ready for review April 3, 2026 19:51

overlookmotel requested a review from camc314 as a code owner April 3, 2026 19:51

Copilot AI review requested due to automatic review settings April 3, 2026 19:51

Copilot started reviewing on behalf of overlookmotel April 3, 2026 19:52 View session

Copilot AI reviewed Apr 3, 2026

View reviewed changes

overlookmotel self-assigned this Apr 3, 2026

This was referenced Apr 3, 2026

perf(napi/parser, linter/plugins): clear buffers and source texts earlier #21025

Merged

refactor(linter/plugins): import getNodeLoc instead of injecting it #21026

Merged

graphite-app bot force-pushed the om/04-03-perf_napi_parser_linter_plugins_raw_transfer_use_string.fromcharcode_in_string_decoding branch from f8c4053 to 9f494c3 Compare April 3, 2026 22:05

graphite-app bot force-pushed the om/04-03-perf_napi_parser_linter_plugins_simplify_branch_condition_in_deserializestr_ branch from a1a5dd2 to c25ef02 Compare April 3, 2026 22:06

Base automatically changed from om/04-03-perf_napi_parser_linter_plugins_raw_transfer_use_string.fromcharcode_in_string_decoding to main April 3, 2026 22:10

graphite-app bot merged commit c25ef02 into main Apr 3, 2026
25 checks passed

graphite-app bot deleted the om/04-03-perf_napi_parser_linter_plugins_simplify_branch_condition_in_deserializestr_ branch April 3, 2026 22:12

This was referenced Apr 6, 2026

release(crates): oxc v0.124.0 #21084

Merged

release(apps): oxlint v1.59.0 && oxfmt v0.44.0 #21085

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

perf(napi/parser, linter/plugins): simplify branch condition in `deserializeStr`#21019

perf(napi/parser, linter/plugins): simplify branch condition in `deserializeStr`#21019
graphite-app[bot] merged 1 commit intomainfrom
om/04-03-perf_napi_parser_linter_plugins_simplify_branch_condition_in_deserializestr_

overlookmotel commented Apr 3, 2026 •

edited

Loading

Uh oh!

overlookmotel commented Apr 3, 2026 •

edited

Loading

Uh oh!

Copilot AI left a comment

Uh oh!

graphite-app bot commented Apr 3, 2026 •

edited

Loading

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Uh oh!

Conversation

overlookmotel commented Apr 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

overlookmotel commented Apr 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

How to use the Graphite Merge Queue

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

graphite-app bot commented Apr 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Merge activity

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

overlookmotel commented Apr 3, 2026 •

edited

Loading

overlookmotel commented Apr 3, 2026 •

edited

Loading

graphite-app bot commented Apr 3, 2026 •

edited

Loading