fix(linter/no-unused-vars): avoid renaming captured vars#22310
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graphite-app Bot
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When `no-unused-vars` renames an unused parameter to satisfy `argsIgnorePattern`, it can accidentally change existing references in the function body.
For example:
```js
const _unused = 1;
function foo(unused) {
return _unused;
}
```
Renaming `unused` to `_unused` would make the body reference the parameter instead of the outer binding. This now detects that capture risk and chooses `_unused0` instead, while still allowing inner-scope bindings that already shadow the name.
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Pull request overview
This PR improves the no-unused-vars fixer’s parameter-renaming logic so that when it renames an unused parameter to satisfy argsIgnorePattern, it avoids choosing a name that would “capture” existing references inside the function body (changing which binding those references resolve to).
Changes:
- Extend conflict-avoidance logic to also reject rename candidates that would capture existing resolved or unresolved references in descendant scopes.
- Add new regression tests covering outer-scope capture and nested-function capture cases, while still allowing inner-scope shadowing.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
crates/oxc_linter/src/rules/eslint/no_unused_vars/fixers/fix_conflicts.rs |
Adds capture-risk detection when synthesizing an ignored name, preventing renames that would change identifier resolution. |
crates/oxc_linter/src/rules/eslint/no_unused_vars/tests/oxc.rs |
Adds fix regression tests for capture-risk scenarios and an inner-scope shadowing “allowed” scenario. |
camc314
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May 11, 2026
When `no-unused-vars` renames an unused parameter to satisfy `argsIgnorePattern`, it can accidentally change existing references in the function body.
For example:
```js
const _unused = 1;
function foo(unused) {
return _unused;
}
```
Renaming `unused` to `_unused` would make the body reference the parameter instead of the outer binding. This now detects that capture risk and chooses `_unused0` instead, while still allowing inner-scope bindings that already shadow the name.
f16d617 to
1889c36
Compare
When `no-unused-vars` renames an unused parameter to satisfy `argsIgnorePattern`, it can accidentally change existing references in the function body.
For example:
```js
const _unused = 1;
function foo(unused) {
return _unused;
}
```
Renaming `unused` to `_unused` would make the body reference the parameter instead of the outer binding. This now detects that capture risk and chooses `_unused0` instead, while still allowing inner-scope bindings that already shadow the name.
1889c36 to
610f4c7
Compare
camc314
added a commit
that referenced
this pull request
May 11, 2026
# Oxlint ### 💥 BREAKING CHANGES - 00ce512 oxlint/lsp: [**BREAKING**] Don't fix suggestions on fixAll code actions & command (#22195) (Sysix) ### 🚀 Features - 0eeceaf linter/no-unused-vars: Rename parameter with initializer (#22308) (camc314) - fa0232b linter/no-unused-vars: Add param rename suggestion (#22285) (Ryota Misumi) - ae59305 linter/promise/no-promise-in-callback: Add `exemptDeclarations` option (#22275) (Mikhail Baev) - 60bed4a linter: Extends `no-redundant-roles` and `prefer-tag-over-role` support roles (#22069) (mehm8128) - 545c80f linter/eslint: Implement `prefer-regex-literals` rule (#22192) (Mikhail Baev) - cf86d7a linter: Bulk suppression (#19328) (Said Atrahouch) - 23abd22 linter/jsx-a11y: Implement no-noninteractive-element-to-interactive-role (#21264) (Pedro Tainha) - fbb8f22 linter: Support `ignores` in overrides (#22148) (camc314) - 5a4414d oxlint/lsp: Support `rulesCustomization` lsp option (#21858) (Sysix) ### 🐛 Bug Fixes - 610f4c7 linter/no-unused-vars: Avoid renaming captured vars (#22310) (camc314) - 6b50f23 oxlint/cli: Load root config by searching up parent directories (#22272) (Sysix) - 31a5de7 linter: Rename override `ignores` to `excludeFiles` (#22283) (camc314) - 26d5d7b linter: Add missing vitest/valid-describe-callback functionality (#22279) (camchenry) - 784530f linter: `valid-title`: detect `String.raw` strings (#22271) (Sysix) - 080d90e linter: Move `no-debugger` fix to suggestion (#22256) (Sysix) - 25b7017 linter: Undocument override `ignores` option (#22213) (camc314) - 7bb00dd linter: Fix role-has-required-aria-props (#22097) (mehm8128) - d25279e linter/disable-directives: Improve parsing of names, descriptions (#22184) (camc314) - a59e447 linter/disable-directives: Ignore invalid enable suffixes (#22179) (camc314) - aafef0f ci: Disable bulk supression test on big endian (#22175) (camc314) - 281daec linter/vue/define-props-destructuring: Add `only-when-assigned` config opt (#22142) (camc314) - 46ab679 linter/plugins: Trim leading newline for partial sources (#20928) (bab) - 29ff6d9 linter: Update docs for no_alias_methods rule to be Vitest-specific and add toThrowError alias (#22129) (camchenry) ### ⚡ Performance - 9414bee linter/role-has-required-aria-props: Avoid intermediate vec (#22212) (camc314) - 3883ea3 linter/no-useless-escape: Drop unnecessary Vec collect (#22171) (connorshea) - 42c3029 linter/check-property-names: Replace split-collect-pop-join with rfind (#22172) (connorshea) - 9551d53 linter: Remove unnecessary Vec collect in CFG edge traversal (#22167) (connorshea) - 26fa2fc linter/aria-role: Remove unnecessary string allocations in run method (#22168) (connorshea) - c9ce045 linter/getter-return: Remove unnecessary Vec collect in CFG edge traversal (#22166) (connorshea) - 72bd846 linter/no-this-in-sfc: Reorder cheap name check, avoid String allocation (#22164) (connorshea) ### 📚 Documentation - 4da212a linter/no-unused-vars: Add docs to `rename_unused_function_parameter` (#22311) (camc314) - 27c4628 linter/forbid-dom-props: Escape jsx examples in lint rule docs (#22254) (4MBL) - 3f81147 linter: Improve the `react/jsx-key` rule docs. (#22162) (connorshea) - 07f03cc linter/consistent-return: Add note about `noImplicitReturns` coverage (#22156) (camc314) - 7c1e049 oxlint/lsp: Improve autogenerated lsp docs (#22154) (Sysix) - 87b3e38 linter: Update docs to be vitest-specific for consistent-test-it (#22128) (camchenry) # Oxfmt ### 💥 BREAKING CHANGES - 5c6c390 oxfmt: [**BREAKING**] Respect more git ignore options, align with Oxlint (#22210) (leaysgur) ### 🚀 Features - 6e8e818 oxfmt: Experimental .svelte support (#21700) (leaysgur) ### 🐛 Bug Fixes - e2a20b6 formatter: Add space after commas in import attributes (#22274) (Leonabcd123) ### ⚡ Performance - b756682 oxfmt: Optimize nested config prescan (#22232) (Jovi De Croock) - f14e81e formatter/sort_imports: Skip sort for single import runs (#22204) (leaysgur) - 32255b1 formatter: Process `ImportDeclaration`s in a run (#22079) (overlookmotel) ### 📚 Documentation - 4da6f4c formatter: Correct comment (#22217) (overlookmotel) - ef3507d formatter/sort_imports: Refresh docs (#22203) (leaysgur) Co-authored-by: Cameron <cameron.clark@hey.com>
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When
no-unused-varsrenames an unused parameter to satisfyargsIgnorePattern, it can accidentally change existing references in the function body.For example:
Renaming
unusedto_unusedwould make the body reference the parameter instead of the outer binding. This now detects that capture risk and chooses_unused0instead, while still allowing inner-scope bindings that already shadow the name.