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feat(eslint-plugin): [no-useless-default-assignment] add rule#11720

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JoshuaKGoldberg merged 41 commits intotypescript-eslint:mainfromulrichstark:feat(eslint-plugin)---no-useless-default-assignment]-add-rule

Dec 14, 2025

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feat(eslint-plugin): [no-useless-default-assignment] add rule#11720

JoshuaKGoldberg merged 41 commits intotypescript-eslint:mainfromulrichstark:feat(eslint-plugin)---no-useless-default-assignment]-add-rule

Dec 14, 2025

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ulrichstark commentedOct 25, 2025•
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PR Checklist

Addresses an existing open issue:fixesRule proposal: Detect useless default in function parameters and object destructuring #6106
That issue was marked asaccepting prs
Steps inContributing were taken

Overview

Reports useless default values.

functionBar({ foo=''}:{foo:string}){returnfoo;}const{ foo=''}={foo:'bar'};const[foo='']=['bar'];[1,2,3].map((a=42)=>a+1);

feat(eslint-plugin): [no-useless-default-assignment] add rule

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typescript-eslintbot commentedOct 25, 2025

Thanks for the PR,@ulrichstark!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

🙏Please, if you or your company is finding typescript-eslint valuable, help us sustain the project by sponsoring it transparently on https://opencollective.com/typescript-eslint.

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View yourCI Pipeline Execution ↗ for commit026fd7f

Command	Status	Duration	Result
`nx test eslint-plugin --coverage=false`	✅ Succeeded	5m 25s	View ↗
`nx run-many -t lint`	✅ Succeeded	3m 15s	View ↗
`nx run-many -t typecheck`	✅ Succeeded	2m 1s	View ↗
`nx run types:build`	✅ Succeeded	1s	View ↗
`nx run integration-tests:test`	✅ Succeeded	6s	View ↗
`nx run generate-configs`	✅ Succeeded	8s	View ↗
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☁️Nx Cloud last updated this comment at2025-12-02 21:41:13 UTC

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.58%. Comparing base (5ac66a6) to head (026fd7f).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@##             main   #11720      +/-   ##==========================================+ Coverage   90.53%   90.58%   +0.04%==========================================  Files         523      524       +1       Lines       53097    53325     +228       Branches     8838     8892      +54     ==========================================+ Hits        48074    48302     +228  Misses       5010     5010                Partials       13       13

Flag	Coverage Δ
unittest	`90.58% <100.00%> (+0.04%)`	⬆️

Flags with carried forward coverage won't be shown.Click here to find out more.

Files with missing lines	Coverage Δ
packages/eslint-plugin/src/configs/eslintrc/all.ts	`100.00% <100.00%> (ø)`
...lugin/src/configs/eslintrc/disable-type-checked.ts	`100.00% <100.00%> (ø)`
...n/src/configs/eslintrc/strict-type-checked-only.ts	`100.00% <100.00%> (ø)`
...plugin/src/configs/eslintrc/strict-type-checked.ts	`100.00% <100.00%> (ø)`
packages/eslint-plugin/src/configs/flat/all.ts	`100.00% <100.00%> (ø)`
...nt-plugin/src/configs/flat/disable-type-checked.ts	`100.00% <100.00%> (ø)`
...lugin/src/configs/flat/strict-type-checked-only.ts	`100.00% <100.00%> (ø)`
...int-plugin/src/configs/flat/strict-type-checked.ts	`100.00% <100.00%> (ø)`
...-plugin/src/rules/no-useless-default-assignment.ts	`100.00% <100.00%> (ø)`

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ulrichstark added5 commits

October 25, 2025 22:58

support function parameters without type annotation

4a8ef6b

fix false positives

7637497

fixing more false positives

7a7b334

enable rule in repo to dogfood

527b367

cleanup code and increase code coverage

010c166

ulrichstark marked this pull request as draft

October 25, 2025 22:13

cleanup code and add column numbers to tests

ff7bd0b

ulrichstark mentioned this pull request

Oct 25, 2025

chore(eslint-plugin): use correct type for return type ofcreateValidator#11721

Merged

3 tasks

add tests to increase test coverage

8d29d31

ulrichstark marked this pull request as ready for review

October 25, 2025 22:59

JoshuaKGoldberg requested changes

Nov 3, 2025

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A great start, I love how readable this implementation is! 👏 nicely done.

Requesting changes mostly on getting test coverage up and covering edge cases. I suspect you'll have to tweak the implementation a little to deal with tuples. Cheers!

packages/eslint-plugin/docs/rules/no-useless-default-assignment.mdx OutdatedShow resolvedHide resolved

packages/eslint-plugin/src/rules/no-useless-default-assignment.ts

		default:
		returnnull;
		}
		}

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[Non-Actionable] I'm surprised a utility doesn't already exist for this - but I couldn't find one.

getStaticValue: doesn't handle identifiers
getStringIfConstant: doesn't handle identifiers (it's a small wrapper aroundgetStaticStringValue)
getStaticStringValue: didn't handle identifiers properly

Not requesting changes, just noting - maybe I missed one?

packages/eslint-plugin/tests/rules/no-useless-default-assignment.test.ts OutdatedShow resolvedHide resolved

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packages/eslint-plugin/docs/rules/no-useless-default-assignment.mdx OutdatedShow resolvedHide resolved

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JoshuaKGoldberg added the awaiting responseIssues waiting for a reply from the OP or another party label

Nov 3, 2025

ulrichstarkand others added8 commits

November 4, 2025 17:03

remove option allowRuleToRunWithoutStrictNullChecksIKnowWhatIAmDoing

df51d1c

remove comments at each test case

0526062

remove rule from rulesWithComplexOptionHeadings

90d121a

update snapshot

9b55fb2

Update packages/eslint-plugin/docs/rules/no-useless-default-assignmen…

422a704

…t.mdxCo-authored-by: Josh Goldberg ✨ <git@joshuakgoldberg.com>

Update packages/eslint-plugin/docs/rules/no-useless-default-assignmen…

16ff0d6

…t.mdxCo-authored-by: Josh Goldberg ✨ <git@joshuakgoldberg.com>

add rule to strict config

4c40bfb

Merge branch 'main' into feat(eslint-plugin)---no-useless-default-ass…

def0e8a

…ignment]-add-rule

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ulrichstark commentedNov 4, 2025

Thanks Josh for your review! I already made all low effort changes. Do you also want me to turn the suggestion into a fix? I think it's safe in every case the project is properly typed.

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JoshuaKGoldberg commentedNov 4, 2025

Yes let's do that 🚀

ulrichstark added3 commits

November 5, 2025 20:11

turn suggestion into fix

6bef7fa

add more test cases and make them pass

299249e

make example code easier to understand and add tuple example

242883a

github-actionsbot removed the 1 approval>=1 team member has approved this PR; we're now leaving it open for more reviews before we merge label

Nov 26, 2025

ulrichstark added2 commits

November 26, 2025 18:39

remove from eslint.config.mjs

37ce842

make "when not to use it" more relevant to this rule

33c859e

ulrichstark dismissedJoshuaKGoldberg’sstale review via33c859e

November 26, 2025 17:44

ulrichstarkand others added2 commits

November 26, 2025 22:21

Merge branch 'main' into feat(eslint-plugin)---no-useless-default-ass…

052981c

…ignment]-add-rule

Merge branch 'main' into feat(eslint-plugin)---no-useless-default-ass…

3c04657

…ignment]-add-rule

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Nov 28, 2025

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Lovely work, thanks! 🙌

@ronami had a bunch of good points I'd missed last review cycle, so if they have time it'd be good to hear from them too.

JoshuaKGoldberg added the 1 approval>=1 team member has approved this PR; we're now leaving it open for more reviews before we merge label

Nov 28, 2025

bradzacher previously approved these changes

Nov 30, 2025

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Dec 1, 2025

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🚀🚀 Looks amazing!

I've added two comments for bugs around destructuring records/mapped-types.

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ulrichstark added4 commits

December 1, 2025 22:16

Merge branch 'main' into feat(eslint-plugin)---no-useless-default-ass…

071c2ef

…ignment]-add-rule

remove unnecessary type assertion

9334493

check for string index type

be81a7f

support compiler option noUncheckedIndexedAccess properly

ed0011c

ulrichstark dismissed stale reviews frombradzacher andJoshuaKGoldberg viaed0011c

December 1, 2025 21:19

ulrichstark requested a review fromronami

December 1, 2025 21:20

github-actionsbot removed the 1 approval>=1 team member has approved this PR; we're now leaving it open for more reviews before we merge label

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ronami reviewed

Dec 2, 2025

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Lovely work! 🏆

Requesting one final adjustment for records/mapped-types around thenoUncheckedIndexedAccess compiler option.

packages/eslint-plugin/src/rules/no-useless-default-assignment.tsShow resolvedHide resolved

also support noUncheckedIndexedAccess for records/mapped types

026fd7f

ulrichstark requested a review fromronami

December 2, 2025 21:30

ronami approved these changes

Dec 3, 2025

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🚀🚀

JoshuaKGoldberg merged commit1301f79 intotypescript-eslint:main

Dec 14, 2025

67 checks passed

ulrichstark deleted the feat(eslint-plugin)---no-useless-default-assignment]-add-rule branch

December 14, 2025 20:21

chrisbbreuer mentioned this pull request

Dec 15, 2025

chore(deps): update all non-major dependenciesstacksjs/eslint-plugin#67

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simPod commentedDec 15, 2025

importtype{TypePolicy}from'@apollo/client';importtype{Foo,Bar}from'@app/gql/graphql';import{replaceArray}from'./helpers';exportconstnetworkPortTypePolicy:TypePolicy={fields:{pduLinks:{merge:(_existing:PduPortLink[]|undefined,incoming:PduPortLink[]=[])=>replaceArray<PduPortLink>(_existing,incoming),},serverLinks:{merge:(_existing:ServerPortLink[]|undefined,incoming:ServerPortLink[]=[])=>replaceArray<ServerPortLink>(_existing,incoming),},},};

ESLint: 8.57.1TypeError: Cannot read properties of undefined (reading 'getParameters')Occurred while linting /builds/myfile.ts:10Rule: "@typescript-eslint/no-useless-default-assignment"    at checkAssignmentPattern (/builds/.yarn/__virtual__/@typescript-eslint-eslint-plugin-virtual-a7bfaa68a3/5/cache/yarn/cache/@typescript-eslint-eslint-plugin-npm-8.50.0-f4ae1c8099-10c0.zip/node_modules/@typescript-eslint/eslint-plugin/dist/rules/no-useless-default-assignment.js:114:54)    at ruleErrorHandler (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/linter.js:1076:28)    at /cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/safe-emitter.js:45:58    at Array.forEach (<anonymous>)    at Object.emit (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/safe-emitter.js:45:38)    at NodeEventGenerator.applySelector (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/node-event-generator.js:297:26)    at NodeEventGenerator.applySelectors (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/node-event-generator.js:326:22)    at NodeEventGenerator.enterNode (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/node-event-generator.js:340:14)    at CodePathAnalyzer.enterNode (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/code-path-analysis/code-path-analyzer.js:803:23)    at /cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/linter.js:1111:32    at Array.forEach (<anonymous>)    at runRules (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/linter.js:1106:15)    at Linter._verifyWithoutProcessors (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/linter.js:1355:31)    at Linter._verifyWithConfigArray (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/linter.js:1807:21)    at Linter.verify (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/linter.js:1437:65)    at Linter.verifyAndFix (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/linter/linter.js:2068:29)    at verifyText (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/cli-engine/cli-engine.js:254:48)    at CLIEngine.executeOnFiles (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/cli-engine/cli-engine.js:834:28)    at ESLint.lintFiles (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/eslint/eslint.js:551:23)    at Object.execute (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/lib/cli.js:421:36)    at async main (/cache/yarn/cache/eslint-npm-8.57.1-dd20287a5a-10c0.zip/node_modules/eslint/bin/eslint.js:152:22)