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fuzz(css_lexer): ensure REPLACEMENT_CHARACTER is appended in small idents - #1213

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fuzz/findings-20260613-030547
Jun 13, 2026
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fuzz(css_lexer): ensure REPLACEMENT_CHARACTER is appended in small idents#1213
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fuzz/findings-20260613-030547

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@keithamus keithamus commented Jun 13, 2026 •
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Nightly fuzz run found new findings.

Given inputs like l\0000, the tokenizer would generate an ident with the value l, which would hit a debug_assert! during parse as the parsed string would be l\u{FFFD}.

This fixes this issue by ensuring the lexer adds REPLACEMENT_CHARACTER to small_ident, so that the ident value is consistently l\u{FFFD}.

GHA run: https://github.com/csskit/csskit/actions/runs/27454595586

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All CI jobs have passed. Approving. (Build jobs were skipped - no build-relevant files changed)

@keithamus keithamus changed the title fuzz: new parser findings 2026-06-13 fuzz(css_lexer): ensure REPLACEMENT_CHARACTER is appended in small idents Jun 13, 2026
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keithamus enabled auto-merge (squash) June 13, 2026 08:08
github-actions[bot]
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All CI jobs have passed. Approving.

@keithamus
keithamus merged commit e69c070 into main Jun 13, 2026
17 of 18 checks passed
@keithamus
keithamus deleted the fuzz/findings-20260613-030547 branch June 13, 2026 08:14
github-actions Bot pushed a commit that referenced this pull request Jun 13, 2026
@keithamus
Release: v0.0.25
2002a37 
## [0.0.25] - 2026-06-13

### Other Changes
- Update cargo deps (#1189) ([#1189](#1189))
- Push allocator-api2 back to 2.21 due to bumpalo (#1191) ([#1191](#1191))
- Fuzz: Try setting up a fuzzing suite (#1201) ([#1201](#1201))

### Css_ast
- css_ast: Avoid hanging on `={-->}` input. (#1183) ([#1183](#1183))
- Regenerate css_ast/src/values from csswg drafts (#1184) ([#1184](#1184))
- css_ast: Use assert_parse! closure macro variant in tests. (#1196) ([#1196](#1196))
- cssast/csskit_derives: Add new FeatureMetadata system (#1197) ([#1197](#1197))
- csskit_derives/css_ast: make derive(IntoCursor) work with generics (#1200) ([#1200](#1200))
- css_ast: Implement a NonEmpty generic (#1202) ([#1202](#1202))

### Css_lexer
- fuzz: early return atom functions when given non-atom tokens (#1206) ([#1206](#1206))
- fuzz(css_lexer): ensure REPLACEMENT_CHARACTER is appended in small idents (#1213) ([#1213](#1213))

### Css_parse
- css_parse: Ensure buffer is refilled if skipping past a whole buffer (#1180) ([#1180](#1180))
- css_parse: Impl ToSpan for Comparison (#1190) ([#1190](#1190))
- Impl Display for Comparison (#1193) ([#1193](#1193))
- css_parse: Improve assert_parse! macros to use a block/closure (#1194) ([#1194](#1194))

### Csskit
- csskit: improve json output for subcommands (#1182) ([#1182](#1182))
- chore(deps): update dependencies (patch) (#1185) ([#1185](#1185))

### Csskit_derives
- csskit_derives: Ensure generics expect Peek when using it. (#1198) ([#1198](#1198))

### Csskit_source_finder
- csskit_source_finder: Don't find visitable nodes that just visit children (#1199) ([#1199](#1199))

### Csskit_vscode
- chore(deps): update dependency @vscode/test-electron to v3 (#1192) ([#1192](#1192))
- fix(deps): update dependency esbuild to v0.28.1 [security] (#1210) ([#1210](#1210))

[forcebuild]
@keithamus keithamus mentioned this pull request Jun 13, 2026
Merged
github-actions Bot pushed a commit that referenced this pull request Jun 13, 2026
@keithamus
Canary Release
5a71ab4 
## [0.0.25] - 2026-06-13

### Other Changes
- Update cargo deps (#1189) ([#1189](#1189))
- Push allocator-api2 back to 2.21 due to bumpalo (#1191) ([#1191](#1191))
- Fuzz: Try setting up a fuzzing suite (#1201) ([#1201](#1201))

### Css_ast
- css_ast: Avoid hanging on `={-->}` input. (#1183) ([#1183](#1183))
- Regenerate css_ast/src/values from csswg drafts (#1184) ([#1184](#1184))
- css_ast: Use assert_parse! closure macro variant in tests. (#1196) ([#1196](#1196))
- cssast/csskit_derives: Add new FeatureMetadata system (#1197) ([#1197](#1197))
- csskit_derives/css_ast: make derive(IntoCursor) work with generics (#1200) ([#1200](#1200))
- css_ast: Implement a NonEmpty generic (#1202) ([#1202](#1202))

### Css_lexer
- fuzz: early return atom functions when given non-atom tokens (#1206) ([#1206](#1206))
- fuzz(css_lexer): ensure REPLACEMENT_CHARACTER is appended in small idents (#1213) ([#1213](#1213))

### Css_parse
- css_parse: Ensure buffer is refilled if skipping past a whole buffer (#1180) ([#1180](#1180))
- css_parse: Impl ToSpan for Comparison (#1190) ([#1190](#1190))
- Impl Display for Comparison (#1193) ([#1193](#1193))
- css_parse: Improve assert_parse! macros to use a block/closure (#1194) ([#1194](#1194))

### Csskit
- csskit: improve json output for subcommands (#1182) ([#1182](#1182))
- chore(deps): update dependencies (patch) (#1185) ([#1185](#1185))

### Csskit_derives
- csskit_derives: Ensure generics expect Peek when using it. (#1198) ([#1198](#1198))

### Csskit_source_finder
- csskit_source_finder: Don't find visitable nodes that just visit children (#1199) ([#1199](#1199))

### Csskit_vscode
- chore(deps): update dependency @vscode/test-electron to v3 (#1192) ([#1192](#1192))
- fix(deps): update dependency esbuild to v0.28.1 [security] (#1210) ([#1210](#1210))
keithamus added a commit that referenced this pull request Jun 13, 2026
@keithamus
Release v0.0.25 (#1181)
a8567c2 
## [0.0.25] - 2026-06-13

### Other Changes
- Update cargo deps (#1189)
([#1189](#1189))
- Push allocator-api2 back to 2.21 due to bumpalo (#1191)
([#1191](#1191))
- Fuzz: Try setting up a fuzzing suite (#1201)
([#1201](#1201))


### Css_ast
- css_ast: Avoid hanging on `={-->}` input. (#1183)
([#1183](#1183))
- Regenerate css_ast/src/values from csswg drafts (#1184)
([#1184](#1184))
- css_ast: Use assert_parse! closure macro variant in tests. (#1196)
([#1196](#1196))
- cssast/csskit_derives: Add new FeatureMetadata system (#1197)
([#1197](#1197))
- csskit_derives/css_ast: make derive(IntoCursor) work with generics
(#1200) ([#1200](#1200))
- css_ast: Implement a NonEmpty generic (#1202)
([#1202](#1202))


### Css_lexer
- fuzz: early return atom functions when given non-atom tokens (#1206)
([#1206](#1206))
- fuzz(css_lexer): ensure REPLACEMENT_CHARACTER is appended in small
idents (#1213) ([#1213](#1213))


### Css_parse
- css_parse: Ensure buffer is refilled if skipping past a whole buffer
(#1180) ([#1180](#1180))
- css_parse: Impl ToSpan for Comparison (#1190)
([#1190](#1190))
- Impl Display for Comparison (#1193)
([#1193](#1193))
- css_parse: Improve assert_parse! macros to use a block/closure (#1194)
([#1194](#1194))


### Csskit
- csskit: improve json output for subcommands (#1182)
([#1182](#1182))
- chore(deps): update dependencies (patch) (#1185)
([#1185](#1185))


### Csskit_derives
- csskit_derives: Ensure generics expect Peek when using it. (#1198)
([#1198](#1198))


### Csskit_source_finder
- csskit_source_finder: Don't find visitable nodes that just visit
children (#1199) ([#1199](#1199))


### Csskit_vscode
- chore(deps): update dependency @vscode/test-electron to v3 (#1192)
([#1192](#1192))
- fix(deps): update dependency esbuild to v0.28.1 [security] (#1210)
([#1210](#1210))
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