fix!: no-unused-vars `varsIgnorePattern` behavior with catch arguments by Tanujkanti4441 · Pull Request #17932 · eslint/eslint

Tanujkanti4441 · 2023-12-30T13:29:23Z

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I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[x] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

Tell us about your environment (npx eslint --env-info):

Node version: 21.1.0
npm version: 10.2.0
Local ESLint version: latest
Global ESLint version: latest
Operating System: windows

What parser are you using (place an "X" next to just one item)?

[x] Default (Espree)
[ ] @typescript-eslint/parser
[ ] @babel/eslint-parser
[ ] vue-eslint-parser
[ ] @angular-eslint/template-parser
[ ] Other

Please show your full configuration:

Configuration

'@typescript-eslint/no-unused-vars': [
      'error',
      {
        varsIgnorePattern: '^err',
        caughtErrors: 'all'
      }
    ]

What did you do? Please include the actual source code causing the issue.

try {
  // ...
} catch (err) { // <== unused variable
  console.error(process.env)
}

What did you expect to happen?
eslint won't ignore the err argument.
What actually happened? Please include the actual, raw output from ESLint.
eslint ignored the err argument by following the varsIgnorePattern.

Fixes: #17540

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nzakas

LGTM. Would like @mdjermanovic to review before merging.

nzakas · 2024-01-02T21:39:02Z

Oops, one more request: because this is a breaking change, can you please add an entry into migrate-to-9.0.0.md under the "Breaking Changes for Users" section?

nzakas

Looking good. Just cleaned up the wording on the migration guide with a few suggestions.

nzakas · 2024-01-03T18:04:01Z

 * [Case-sensitive flags in `no-invalid-regexp`](#no-invalid-regexp)
 * [Stricter `/* exported */` parsing](#exported-parsing)
 * [`"eslint:recommended"` and `"eslint:all"` strings no longer accepted in flat config](#string-config)
+* [Behavior of `varsIgnorePattern` option of `no-unused-vars` rule with catch arguments](#vars-ignore-pattern)


Suggested change

* [Behavior of `varsIgnorePattern` option of `no-unused-vars` rule with catch arguments](#vars-ignore-pattern)

* [`varsIgnorePattern` option of `no-unused-vars` no longer applies to catch arguments](#vars-ignore-pattern)

nzakas · 2024-01-03T18:04:21Z


 **Related issue(s):** [#17488](https://github.com/eslint/eslint/issues/17488)

+## <a name="vars-ignore-pattern"></a> Behavior of `varsIgnorePattern` option of `no-unused-vars` rule with catch arguments


Suggested change

## <a name="vars-ignore-pattern"></a> Behavior of `varsIgnorePattern` option of `no-unused-vars` rule with catch arguments

## <a name="vars-ignore-pattern"></a> `varsIgnorePattern` option of `no-unused-vars` no longer applies to catch arguments

nzakas · 2024-01-03T18:08:00Z

+In previous versions of ESLint, `varsIgnorePattern` option of `no-unused-vars`, that is used to restrict some specified variable to be reported, used to ignore all variables that machtes the specified pattern except `function` arguments because there is a seperate option to ignore them called `argsIgnorePattern` and same was expected for `caughtErrorsIgnorePattern` option but `varsIgnorePattern` was also ignoring `catch` block arguments.
+
+This behavior has been fixed in ESLint v9.0.0, that means `varsIgnorePattern` option don't get applied to both `function` and `catch` block arguments.


Suggested change

In previous versions of ESLint, `varsIgnorePattern` option of `no-unused-vars`, that is used to restrict some specified variable to be reported, used to ignore all variables that machtes the specified pattern except `function` arguments because there is a seperate option to ignore them called `argsIgnorePattern` and same was expected for `caughtErrorsIgnorePattern` option but `varsIgnorePattern` was also ignoring `catch` block arguments.

This behavior has been fixed in ESLint v9.0.0, that means `varsIgnorePattern` option don't get applied to both `function` and `catch` block arguments.

In previous versions of ESLint, the `varsIgnorePattern` option of `no-unused-vars` incorrectly ignored errors specified in a `catch` clause. In ESLint v9.0.0, `varsIgnorePattern` no longer applies to errors in `catch` clauses. For example:

nzakas · 2024-01-03T18:09:25Z

+
+```
+
+**Related issue(s):** [#17540](https://github.com/eslint/eslint/issues/17540)


Suggested change

**Related issue(s):** [#17540](https://github.com/eslint/eslint/issues/17540)

**To address:** If you want to specify ignore patterns for `catch` clause variable names, use the `caughtErrorsIgnorePattern` option in addition to `varsIgnorePattern`.

**Related issue(s):** [#17540](https://github.com/eslint/eslint/issues/17540)

snitin315

LGTM, thanks!

we could also add "none" value to vars setting, just like args and catchErrors

The original issue also mentions adding "none" for vars, should we support this?

mdjermanovic · 2024-01-04T10:26:14Z

The original issue also mentions adding "none" for vars, should we support this?

I think that should be a separate issue.

mdjermanovic

LGTM, thanks!

Upgrade to eslint v9 flat config. Custom eslint rules have been tested and work in the new config file. Removed unused vars in try catch blocks due to[ breaking change in eslint v9](eslint/eslint#17932). Use [globals](https://www.npmjs.com/package/globals) to include [globals env](https://eslint.org/docs/latest/use/configure/language-options#predefined-global-variables)

feat: fix varsIgnorePattern behavior

6fbbd3f

Tanujkanti4441 requested a review from a team as a code owner December 30, 2023 13:29

eslint-github-bot bot added breaking This change is backwards-incompatible feature This change adds a new feature to ESLint labels Dec 30, 2023

Tanujkanti4441 changed the title ~~feat!: fix varsIgnorePattern behavior~~ fix!: varsIgnorePattern behavior with catch arguments Dec 30, 2023

eslint-github-bot bot added the bug ESLint is working incorrectly label Dec 30, 2023

snitin315 reviewed Dec 31, 2023

View reviewed changes

Comment thread lib/rules/no-unused-vars.js

snitin315 reviewed Dec 31, 2023

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Comment thread tests/lib/rules/no-unused-vars.js Outdated

update docs and catchClause ignore error message

96e79c3

snitin315 requested changes Jan 1, 2024

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Comment thread tests/lib/rules/no-unused-vars.js

Comment thread docs/src/rules/no-unused-vars.md Outdated

Comment thread docs/src/rules/no-unused-vars.md Outdated

Comment thread docs/src/rules/no-unused-vars.md Outdated

Comment thread docs/src/rules/no-unused-vars.md

snitin315 added the accepted There is consensus among the team that this change meets the criteria for inclusion label Jan 1, 2024

update docs and tests

92298dc

nzakas approved these changes Jan 2, 2024

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docs: add entry to v9 migrate page

1e72d73

nzakas approved these changes Jan 3, 2024

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update migrate guide wordings

741cfb6

snitin315 approved these changes Jan 4, 2024

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mdjermanovic approved these changes Jan 4, 2024

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mdjermanovic changed the title ~~fix!: varsIgnorePattern behavior with catch arguments~~ fix!: no-unused-vars varsIgnorePattern behavior with catch arguments Jan 4, 2024

mdjermanovic merged commit 3ee0f6c into eslint:main Jan 4, 2024

Tanujkanti4441 deleted the ignore-pattern branch January 5, 2024 09:01

JoshuaKGoldberg mentioned this pull request Apr 22, 2024

feat(eslint-plugin): [no-unused-vars] align catch behavior to ESLint 9 typescript-eslint/typescript-eslint#8971

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This was referenced May 15, 2024

chore: upgrade to eslint9 dequelabs/axe-core#4462

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chore: update to support eslint 9 flat config dequelabs/axe-api-team-public#167

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eslint-github-bot bot locked and limited conversation to collaborators Jul 3, 2024

eslint-github-bot bot added the archived due to age This issue has been archived; please open a new issue for any further discussion label Jul 3, 2024

	* [Behavior of `varsIgnorePattern` option of `no-unused-vars` rule with catch arguments](#vars-ignore-pattern)
	* [`varsIgnorePattern` option of `no-unused-vars` no longer applies to catch arguments](#vars-ignore-pattern)


		Related issue(s): [#17488](https://github.com/eslint/eslint/issues/17488)

		## <a name="vars-ignore-pattern"></a> Behavior of `varsIgnorePattern` option of `no-unused-vars` rule with catch arguments

	## <a name="vars-ignore-pattern"></a> Behavior of `varsIgnorePattern` option of `no-unused-vars` rule with catch arguments
	## <a name="vars-ignore-pattern"></a> `varsIgnorePattern` option of `no-unused-vars` no longer applies to catch arguments

		In previous versions of ESLint, `varsIgnorePattern` option of `no-unused-vars`, that is used to restrict some specified variable to be reported, used to ignore all variables that machtes the specified pattern except `function` arguments because there is a seperate option to ignore them called `argsIgnorePattern` and same was expected for `caughtErrorsIgnorePattern` option but `varsIgnorePattern` was also ignoring `catch` block arguments.

		This behavior has been fixed in ESLint v9.0.0, that means `varsIgnorePattern` option don't get applied to both `function` and `catch` block arguments.


		```

		Related issue(s): [#17540](https://github.com/eslint/eslint/issues/17540)

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Tanujkanti4441 commented Dec 30, 2023 •

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