fix(regular_expression): preserve UnicodeEscape CharacterKind in string literals by Boshen · Pull Request #18998 · oxc-project/oxc

Boshen · 2026-02-05T15:15:29Z

Summary

When parsing regex patterns from string literals (e.g., RegExp("[A\\u0301]")), unicode escape sequences were incorrectly identified as CharacterKind::Symbol instead of CharacterKind::UnicodeEscape.

Before:

RegExp("[A\u0301]")
// Character { value: 769, kind: Symbol }  // Wrong!

After:

RegExp("[A\u0301]")
// Character { value: 769, kind: UnicodeEscape }  // Correct!

The fix adds escape kind tracking through the parsing pipeline:

Added EscapeKind enum to CodePoint to track how characters were written in source
StringLiteralParser and TemplateLiteralParser now track unicode (\uXXXX, \u{XXXX}) and hex (\xXX) escapes
PatternParser uses this information when assigning CharacterKind

Closes #13660

🤖 Generated with Claude Code

Copilot

Pull request overview

This PR fixes a bug where unicode escape sequences in RegExp string literals (e.g., RegExp("[A\\u0301]")) were incorrectly identified as CharacterKind::Symbol instead of CharacterKind::UnicodeEscape. The fix adds escape kind tracking through the parsing pipeline to preserve information about how characters were written in source code.

Changes:

Added EscapeKind enum to track unicode (\uXXXX, \u{XXXX}) and hexadecimal (\xXX) escapes through parsing
Modified string literal and template literal parsers to track escape kinds
Updated pattern parser to use escape kind information when creating Character AST nodes
Added tests to verify the fix

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
`crates/oxc_regular_expression/src/parser/reader/ast.rs`	Adds `EscapeKind` enum and `escape_kind` field to `CodePoint` struct
`crates/oxc_regular_expression/src/parser/reader/string_literal_parser/parser_impl.rs`	Updates string literal parser to track unicode and hex escapes via `EscapeKind`
`crates/oxc_regular_expression/src/parser/reader/template_literal_parser/parser_impl.rs`	Updates template literal parser to track unicode and hex escapes via `EscapeKind`
`crates/oxc_regular_expression/src/parser/reader/reader_impl.rs`	Adds `peek_escape_kind()` method to access escape kind information
`crates/oxc_regular_expression/src/parser/pattern_parser/pattern_parser_impl.rs`	Adds conversion helper and updates all non-escaped character creation sites to use escape kind
`crates/oxc_regular_expression/src/parser/reader/mod.rs`	Adds test for escape kind tracking behavior
`crates/oxc_regular_expression/src/parser/mod.rs`	Adds integration test verifying the fix for issue #13660

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codspeed-hq · 2026-02-05T15:21:37Z

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing fix/regexp-unicode-escape-kind (66881ba) with main (384abae)}

Summary

✅ 46 untouched benchmarks
⏩ 3 skipped benchmarks¹

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. ↩

Sysix · 2026-02-05T17:45:24Z

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leaysgur · 2026-02-06T00:36:32Z

Merge activity

Feb 6, 12:36 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Feb 6, 12:36 AM UTC: leaysgur added this pull request to the Graphite merge queue.
Feb 6, 12:43 AM UTC: Merged by the Graphite merge queue.

…ng literals (#18998) ## Summary When parsing regex patterns from string literals (e.g., `RegExp("[A\\u0301]")`), unicode escape sequences were incorrectly identified as `CharacterKind::Symbol` instead of `CharacterKind::UnicodeEscape`. **Before:** ``` RegExp("[A\u0301]") // Character { value: 769, kind: Symbol } // Wrong! ``` **After:** ``` RegExp("[A\u0301]") // Character { value: 769, kind: UnicodeEscape } // Correct! ``` The fix adds escape kind tracking through the parsing pipeline: - Added `EscapeKind` enum to `CodePoint` to track how characters were written in source - `StringLiteralParser` and `TemplateLiteralParser` now track unicode (`\uXXXX`, `\u{XXXX}`) and hex (`\xXX`) escapes - `PatternParser` uses this information when assigning `CharacterKind` Closes #13660 🤖 Generated with [Claude Code](https://claude.ai/code)

after #18998 the tests are now passing now

### 💥 BREAKING CHANGES - 2bf7293 mangler: [**BREAKING**] Enable `top_level` by default for modules and commonjs (#18278) (sapphi-red) - 48b0542 span: [**BREAKING**] SourceType::ts should set module to unambigious (#18873) (Boshen) ### 🚀 Features - 500d071 minifier: Local traverse ctx and generated minifier traverse (#19106) (Boshen) - 142a1be parser: Detect binary files with TS1490 error (#19047) (Boshen) - e316857 allocator/bitset: Add `Ones` iterator to `BitSet` (#19027) (sapphi-red) - 742ad3f minifier: Default `invalid_import_side_effects` to `false` (#18916) (sapphi-red) - 0eff6be parser: Error JSX-like type assertions and generics in `.mts`/`.cts` (#18910) (Boshen) - 18320c6 span: Store file extension in `SourceType` (#18893) (Boshen) ### 🐛 Bug Fixes - a7514e4 isolated-declarations: Preserve const context in literal type inference (#19178) (camc314) - 312e756 isolated-declarations: Preserve readonly literal initializers (#19177) (camc314) - d0ca8d0 isolated-declarations: Skip parenthesis when inferring type (#19176) (camc314) - 110c300 oxc_ecmascript: `+[false]` and `+[true]` should evaluate to `NaN` (#19174) (copilot-swe-agent) - f32ea19 semantic: Report redeclaration error for import bindings conflicting with value declarations (#19068) (Boshen) - 3aeba7a semantic: Report redeclaration error for `function a() {} var a` in module mode (#19041) (Boshen) - 35e32c6 coverage: Match Babel's options.json inheritance for test fixtures (#19002) (Boshen) - 463d60d semantic: Skip TS2391 for standalone computed-name class methods (#19025) (Boshen) - 56c086b parser: Add modifier ordering validation (TS1029) (#19024) (Boshen) - 6067a49 linter/jsdoc: False positive in `check-tag-names` for `@` in email addresses and npm scopes (#19021) (Boshen) - b13bb70 semantic/jsdoc: Inline tags like `{@link}` break jsdoc parsing (#19019) (Boshen) - e3609e3 regular_expression: Preserve UnicodeEscape CharacterKind in string literals (#18998) (Boshen) - 57917ee parser: Parse decorators on rest parameters (#18938) (Boshen) - 487601b napi: Disable mimalloc on Windows to fix worker_threads crash (#18923) (Boshen) - 1f6b193 parser: Validate TypeScript import type options (#18889) (Boshen) - 1663184 parser: Allow conditional types in function type parameters (#18886) (Boshen) - 5758046 parser: Error on property access after instantiation expression (#18887) (Boshen) - 5eb4a94 parser: Handle `<<` as two `<` tokens in type argument contexts (#18885) (Boshen) ### ⚡ Performance - ed8c054 oxc_str: Add precomputed hash to Ident for fast HashMap lookups (#19143) (Boshen) - d4a0867 transformer_plugins: Switch ReplaceGlobalDefines from Traverse to VisitMut (#19146) (Boshen) - 9eb16b3 syntax: Pack ASCII identifier tables into single bitflag table (#19088) (Boshen) - e7595d1 mangler: Use BitSet for exported symbols set (#19023) (sapphi-red) - 2537924 semantic: Optimize scope resolution with fast paths and inlining (#19029) (Boshen) - 69a8d85 mangler: Use BitSet for keep_names symbols set (#19028) (sapphi-red) - f78c525 parser: Try hybrid parsing for jsx children and closing element/fragments (#18789) (camchenry) Co-authored-by: camc314 <[email protected]>

### 💥 BREAKING CHANGES - 2bf7293 mangler: [**BREAKING**] Enable `top_level` by default for modules and commonjs (oxc-project#18278) (sapphi-red) - 48b0542 span: [**BREAKING**] SourceType::ts should set module to unambigious (oxc-project#18873) (Boshen) ### 🚀 Features - 500d071 minifier: Local traverse ctx and generated minifier traverse (oxc-project#19106) (Boshen) - 142a1be parser: Detect binary files with TS1490 error (oxc-project#19047) (Boshen) - e316857 allocator/bitset: Add `Ones` iterator to `BitSet` (oxc-project#19027) (sapphi-red) - 742ad3f minifier: Default `invalid_import_side_effects` to `false` (oxc-project#18916) (sapphi-red) - 0eff6be parser: Error JSX-like type assertions and generics in `.mts`/`.cts` (oxc-project#18910) (Boshen) - 18320c6 span: Store file extension in `SourceType` (oxc-project#18893) (Boshen) ### 🐛 Bug Fixes - a7514e4 isolated-declarations: Preserve const context in literal type inference (oxc-project#19178) (camc314) - 312e756 isolated-declarations: Preserve readonly literal initializers (oxc-project#19177) (camc314) - d0ca8d0 isolated-declarations: Skip parenthesis when inferring type (oxc-project#19176) (camc314) - 110c300 oxc_ecmascript: `+[false]` and `+[true]` should evaluate to `NaN` (oxc-project#19174) (copilot-swe-agent) - f32ea19 semantic: Report redeclaration error for import bindings conflicting with value declarations (oxc-project#19068) (Boshen) - 3aeba7a semantic: Report redeclaration error for `function a() {} var a` in module mode (oxc-project#19041) (Boshen) - 35e32c6 coverage: Match Babel's options.json inheritance for test fixtures (oxc-project#19002) (Boshen) - 463d60d semantic: Skip TS2391 for standalone computed-name class methods (oxc-project#19025) (Boshen) - 56c086b parser: Add modifier ordering validation (TS1029) (oxc-project#19024) (Boshen) - 6067a49 linter/jsdoc: False positive in `check-tag-names` for `@` in email addresses and npm scopes (oxc-project#19021) (Boshen) - b13bb70 semantic/jsdoc: Inline tags like `{@link}` break jsdoc parsing (oxc-project#19019) (Boshen) - e3609e3 regular_expression: Preserve UnicodeEscape CharacterKind in string literals (oxc-project#18998) (Boshen) - 57917ee parser: Parse decorators on rest parameters (oxc-project#18938) (Boshen) - 487601b napi: Disable mimalloc on Windows to fix worker_threads crash (oxc-project#18923) (Boshen) - 1f6b193 parser: Validate TypeScript import type options (oxc-project#18889) (Boshen) - 1663184 parser: Allow conditional types in function type parameters (oxc-project#18886) (Boshen) - 5758046 parser: Error on property access after instantiation expression (oxc-project#18887) (Boshen) - 5eb4a94 parser: Handle `<<` as two `<` tokens in type argument contexts (oxc-project#18885) (Boshen) ### ⚡ Performance - ed8c054 oxc_str: Add precomputed hash to Ident for fast HashMap lookups (oxc-project#19143) (Boshen) - d4a0867 transformer_plugins: Switch ReplaceGlobalDefines from Traverse to VisitMut (oxc-project#19146) (Boshen) - 9eb16b3 syntax: Pack ASCII identifier tables into single bitflag table (oxc-project#19088) (Boshen) - e7595d1 mangler: Use BitSet for exported symbols set (oxc-project#19023) (sapphi-red) - 2537924 semantic: Optimize scope resolution with fast paths and inlining (oxc-project#19029) (Boshen) - 69a8d85 mangler: Use BitSet for keep_names symbols set (oxc-project#19028) (sapphi-red) - f78c525 parser: Try hybrid parsing for jsx children and closing element/fragments (oxc-project#18789) (camchenry) Co-authored-by: camc314 <[email protected]>

…project#19005) after oxc-project#18998 the tests are now passing now

### 💥 BREAKING CHANGES - 2bf7293 mangler: [**BREAKING**] Enable `top_level` by default for modules and commonjs (oxc-project#18278) (sapphi-red) - 48b0542 span: [**BREAKING**] SourceType::ts should set module to unambigious (oxc-project#18873) (Boshen) ### 🚀 Features - 500d071 minifier: Local traverse ctx and generated minifier traverse (oxc-project#19106) (Boshen) - 142a1be parser: Detect binary files with TS1490 error (oxc-project#19047) (Boshen) - e316857 allocator/bitset: Add `Ones` iterator to `BitSet` (oxc-project#19027) (sapphi-red) - 742ad3f minifier: Default `invalid_import_side_effects` to `false` (oxc-project#18916) (sapphi-red) - 0eff6be parser: Error JSX-like type assertions and generics in `.mts`/`.cts` (oxc-project#18910) (Boshen) - 18320c6 span: Store file extension in `SourceType` (oxc-project#18893) (Boshen) ### 🐛 Bug Fixes - a7514e4 isolated-declarations: Preserve const context in literal type inference (oxc-project#19178) (camc314) - 312e756 isolated-declarations: Preserve readonly literal initializers (oxc-project#19177) (camc314) - d0ca8d0 isolated-declarations: Skip parenthesis when inferring type (oxc-project#19176) (camc314) - 110c300 oxc_ecmascript: `+[false]` and `+[true]` should evaluate to `NaN` (oxc-project#19174) (copilot-swe-agent) - f32ea19 semantic: Report redeclaration error for import bindings conflicting with value declarations (oxc-project#19068) (Boshen) - 3aeba7a semantic: Report redeclaration error for `function a() {} var a` in module mode (oxc-project#19041) (Boshen) - 35e32c6 coverage: Match Babel's options.json inheritance for test fixtures (oxc-project#19002) (Boshen) - 463d60d semantic: Skip TS2391 for standalone computed-name class methods (oxc-project#19025) (Boshen) - 56c086b parser: Add modifier ordering validation (TS1029) (oxc-project#19024) (Boshen) - 6067a49 linter/jsdoc: False positive in `check-tag-names` for `@` in email addresses and npm scopes (oxc-project#19021) (Boshen) - b13bb70 semantic/jsdoc: Inline tags like `{@link}` break jsdoc parsing (oxc-project#19019) (Boshen) - e3609e3 regular_expression: Preserve UnicodeEscape CharacterKind in string literals (oxc-project#18998) (Boshen) - 57917ee parser: Parse decorators on rest parameters (oxc-project#18938) (Boshen) - 487601b napi: Disable mimalloc on Windows to fix worker_threads crash (oxc-project#18923) (Boshen) - 1f6b193 parser: Validate TypeScript import type options (oxc-project#18889) (Boshen) - 1663184 parser: Allow conditional types in function type parameters (oxc-project#18886) (Boshen) - 5758046 parser: Error on property access after instantiation expression (oxc-project#18887) (Boshen) - 5eb4a94 parser: Handle `<<` as two `<` tokens in type argument contexts (oxc-project#18885) (Boshen) ### ⚡ Performance - ed8c054 oxc_str: Add precomputed hash to Ident for fast HashMap lookups (oxc-project#19143) (Boshen) - d4a0867 transformer_plugins: Switch ReplaceGlobalDefines from Traverse to VisitMut (oxc-project#19146) (Boshen) - 9eb16b3 syntax: Pack ASCII identifier tables into single bitflag table (oxc-project#19088) (Boshen) - e7595d1 mangler: Use BitSet for exported symbols set (oxc-project#19023) (sapphi-red) - 2537924 semantic: Optimize scope resolution with fast paths and inlining (oxc-project#19029) (Boshen) - 69a8d85 mangler: Use BitSet for keep_names symbols set (oxc-project#19028) (sapphi-red) - f78c525 parser: Try hybrid parsing for jsx children and closing element/fragments (oxc-project#18789) (camchenry) Co-authored-by: camc314 <[email protected]>

Boshen requested a review from leaysgur as a code owner February 5, 2026 15:15

Copilot AI review requested due to automatic review settings February 5, 2026 15:15

github-actions bot added the C-bug Category - Bug label Feb 5, 2026

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Sysix force-pushed the fix/regexp-unicode-escape-kind branch from 81e896f to 66881ba Compare February 5, 2026 17:45

This was referenced Feb 5, 2026

test(linter): enable more no-misleading-character-class tests #19005

Merged

feat(linter): move no-misleading-chracter-class to correctness #19006

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Sysix approved these changes Feb 5, 2026

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graphite-app bot force-pushed the fix/regexp-unicode-escape-kind branch from 66881ba to e3609e3 Compare February 6, 2026 00:37

graphite-app bot merged commit e3609e3 into main Feb 6, 2026
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graphite-app bot deleted the fix/regexp-unicode-escape-kind branch February 6, 2026 00:43

leaysgur mentioned this pull request Feb 6, 2026

regexp: UnicodeEscape Character inside StringLiteral is not correctly detected #13660

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graphite-app bot pushed a commit that referenced this pull request Feb 6, 2026

test(linter): enable more no-misleading-character-class tests (#19005)

a308b42

after #18998 the tests are now passing now

graphite-app bot pushed a commit that referenced this pull request Feb 6, 2026

test(linter): enable more no-misleading-character-class tests (#19005)

f0df9ed

after #18998 the tests are now passing now

connorshea mentioned this pull request Feb 7, 2026

linter: Difference in eslint/no-misleading-character-class violations vs original rule #19090

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This was referenced Feb 9, 2026

release(crates): oxc v0.113.0 #19167

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release(crates): oxc v0.113.0 #19210

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Boshen mentioned this pull request Feb 10, 2026

release(crates): oxc v0.113.0 #19215

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OskarLebuda pushed a commit to OskarLebuda/oxc that referenced this pull request Feb 17, 2026

test(linter): enable more no-misleading-character-class tests (oxc-…

103b746

…project#19005) after oxc-project#18998 the tests are now passing now

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fix(regular_expression): preserve UnicodeEscape CharacterKind in string literals#18998

fix(regular_expression): preserve UnicodeEscape CharacterKind in string literals#18998
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