feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and parameter location arrays as single-use #9536

jfet97 · 2024-07-10T18:32:06Z

PR Checklist

Addresses an existing open issue: fixes Enhancement: [no-unnecessary-type-parameters] Special case tuples and parameter arrays as a "single use" generic type #9529
That issue was marked as accepting prs
Steps in Contributing were taken

Overview

Based on initial work from @danvk, this PR special cases readonly T[], T[], ReadonlyArray<T>, Array<T> and tuples as single use generic types.

typescript-eslint · 2024-07-10T18:32:08Z

Thanks for the PR, @jfet97!

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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.

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codecov · 2024-07-10T19:01:39Z

Codecov Report

Attention: Patch coverage is 84.61538% with 2 lines in your changes missing coverage. Please review.

Project coverage is 87.27%. Comparing base (4a58e98) to head (fc006d3).
Report is 223 commits behind head on main.

❗ Current head fc006d3 differs from pull request most recent head 8a24eca

Please upload reports for the commit 8a24eca to get more accurate results.

Files with missing lines	Patch %	Lines
...plugin/src/rules/no-unnecessary-type-parameters.ts	84.61%	0 Missing and 2 partials ⚠️

❌ Your patch status has failed because the patch coverage (84.61%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9536      +/-   ##
==========================================
+ Coverage   86.76%   87.27%   +0.51%     
==========================================
  Files         444      453       +9     
  Lines       15311    15841     +530     
  Branches     4457     4647     +190     
==========================================
+ Hits        13285    13826     +541     
+ Misses       1672     1658      -14     
- Partials      354      357       +3

Flag	Coverage Δ
unittest	`87.27% <84.61%> (+0.51%)`	⬆️

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

Files with missing lines	Coverage Δ
...plugin/src/rules/no-unnecessary-type-parameters.ts	`92.16% <84.61%> (-0.24%)`	⬇️

... and 159 files with indirect coverage changes

packages/eslint-plugin/src/rules/no-unnecessary-type-parameters.ts

packages/eslint-plugin/tests/rules/no-unnecessary-type-parameters.test.ts

JoshuaKGoldberg

Hey thanks for sending this in & iterating on it! I think the direction here might be a big different from the issue? Did I misread something?

packages/eslint-plugin/tests/rules/no-unnecessary-type-parameters.test.ts

JoshuaKGoldberg

Yup, LGTM - thanks for the iteration!

packages/eslint-plugin/docs/rules/no-unnecessary-type-parameters.mdx

packages/eslint-plugin/src/rules/no-unnecessary-type-parameters.ts

kirkwaiblinger · 2025-02-26T16:47:26Z

There's a parenthesization bug around the suggestion fixer - it fixes this:

class Joiner {
  join<T extends string | number>(els: T[]) {
    return els.map(el => '' + el).join(',');
  }
}

to this:

class Joiner {
  join(els: string | number[]) {
    return els.map(el => '' + el).join(',');
  }
}

That might be worsened by this PR due to it now reporting on T[] syntax, but I think it's an existing bug (you could probably come up with a test case with some wonky intersections/unions precedence), so IMO we can handle it in a followup.

kirkwaiblinger

Exciting!

kirkwaiblinger · 2025-02-27T07:04:45Z

Filed #10894 to follow up on #9536 (comment)

JoshuaKGoldberg

So relieved to have this through 🫠 thanks so much everyone for working on this! 🚀

JoshuaKGoldberg · 2025-03-02T05:47:37Z

CI failures are unrelated on main too. 🚢

@jfet97

| datasource | package | from | to | | ---------- | -------------------------------- | ------ | ------ | | npm | @typescript-eslint/eslint-plugin | 8.24.0 | 8.26.0 | | npm | @typescript-eslint/parser | 8.24.0 | 8.26.0 | ## [v8.26.0](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8260-2025-03-03) ##### 🚀 Features - **eslint-plugin:** \[unified-signatures] support ignoring overload signatures with different JSDoc comments ([#10781](typescript-eslint/typescript-eslint#10781)) - **eslint-plugin:** \[explicit-module-boundary-types] add an option to ignore overload implementations ([#10889](typescript-eslint/typescript-eslint#10889)) - **eslint-plugin:** \[no-unused-var] handle implicit exports in declaration files ([#10714](typescript-eslint/typescript-eslint#10714)) - support TypeScript 5.8 ([#10903](typescript-eslint/typescript-eslint#10903)) - **eslint-plugin:** \[no-unnecessary-type-parameters] special case tuples and parameter location arrays as single-use ([#9536](typescript-eslint/typescript-eslint#9536)) ##### 🩹 Fixes - **eslint-plugin:** \[no-unnecessary-type-assertion] handle unknown ([#10875](typescript-eslint/typescript-eslint#10875)) - **eslint-plugin:** \[no-invalid-void-type] report `accessor` properties with an invalid `void` type ([#10864](typescript-eslint/typescript-eslint#10864)) - **eslint-plugin:** \[unified-signatures] does not differentiate truly private methods ([#10806](typescript-eslint/typescript-eslint#10806)) ##### ❤️ Thank You - Andrea Simone Costa [@jfet97](https://github.com/jfet97) - Dirk Luijk [@dirkluijk](https://github.com/dirkluijk) - Ronen Amiel - YeonJuan [@yeonjuan](https://github.com/yeonjuan) - Yukihiro Hasegawa [@y-hsgw](https://github.com/y-hsgw) You can read about our [versioning strategy](https://main--typescript-eslint.netlify.app/users/versioning) and [releases](https://main--typescript-eslint.netlify.app/users/releases) on our website. ## [v8.25.0](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8250-2025-02-24) ##### 🚀 Features - **eslint-plugin:** \[no-misused-spread] add suggestions ([#10719](typescript-eslint/typescript-eslint#10719)) ##### 🩹 Fixes - **eslint-plugin:** \[prefer-nullish-coalescing] report on chain expressions in a ternary ([#10708](typescript-eslint/typescript-eslint#10708)) - **eslint-plugin:** \[no-deprecated] report usage of deprecated private identifiers ([#10844](typescript-eslint/typescript-eslint#10844)) - **eslint-plugin:** \[unified-signatures] handle getter-setter ([#10818](typescript-eslint/typescript-eslint#10818)) ##### ❤️ Thank You - Olivier Zalmanski [@OlivierZal](https://github.com/OlivierZal) - Ronen Amiel - YeonJuan [@yeonjuan](https://github.com/yeonjuan) You can read about our [versioning strategy](https://main--typescript-eslint.netlify.app/users/versioning) and [releases](https://main--typescript-eslint.netlify.app/users/releases) on our website. ## [v8.24.1](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8241-2025-02-17) ##### 🩹 Fixes - **eslint-plugin:** \[class-methods-use-this] check `accessor` methods with a function initializer ([#10796](typescript-eslint/typescript-eslint#10796)) - **eslint-plugin:** \[no-misused-promises] don't report on `static` `accessor` properties ([#10814](typescript-eslint/typescript-eslint#10814)) - **eslint-plugin:** \[no-deprecated] don't report on deprecated `accessor` property declaration ([#10813](typescript-eslint/typescript-eslint#10813)) - **eslint-plugin:** \[explicit-member-accessibility] check `accessor` class properties for missing accessibility modifier ([#10805](typescript-eslint/typescript-eslint#10805)) - **eslint-plugin:** \[explicit-module-boundary-types] check `accessor` class properties with a function initializer ([#10804](typescript-eslint/typescript-eslint#10804)) - **eslint-plugin:** \[prefer-return-this-type] check `accessor` properties with a function initializer ([#10794](typescript-eslint/typescript-eslint#10794)) - **eslint-plugin:** \[consistent-generic-constructors] check `accessor` class properties ([#10789](typescript-eslint/typescript-eslint#10789)) - **eslint-plugin:** \[no-unsafe-assignment] report on an `any` value assigned as an initializer of an `accessor` property ([#10785](typescript-eslint/typescript-eslint#10785)) - **eslint-plugin:** \[no-unnecessary-template-expression] ignore enum and enum members ([#10782](typescript-eslint/typescript-eslint#10782)) - **eslint-plugin:** \[no-inferrable-types] handle accessor ([#10780](typescript-eslint/typescript-eslint#10780)) ##### ❤️ Thank You - Ronen Amiel - YeonJuan You can read about our [versioning strategy](https://main--typescript-eslint.netlify.app/users/versioning) and [releases](https://main--typescript-eslint.netlify.app/users/releases) on our website.

jfet97 added 10 commits July 10, 2024 17:38

wip 2 usages

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move tests

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add tests

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restore tests

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point failing tests

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fix possible undefined symbol

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left a comment

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ok

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add test

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update doc

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Merge branch 'main' into main

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jfet97 added 3 commits July 10, 2024 22:13

chore: consider existing assumeMultipleUses value

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add missing test case

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doc

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danvk mentioned this pull request Jul 10, 2024

Enhancement: [no-unnecessary-type-parameters] Special case tuples and parameter arrays as a "single use" generic type #9529

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jfet97 and others added 2 commits July 12, 2024 18:20

no error for factory functions

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Merge branch 'main' into main

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jfet97 and others added 3 commits July 16, 2024 09:44

add more tests

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Merge remote-tracking branch 'upstream/main'

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JoshuaKGoldberg changed the title ~~feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and arrays as a "single use" generic type in functions~~ feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and return location arrays as single-use Jan 7, 2025

JoshuaKGoldberg changed the title ~~feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and return location arrays as single-use~~ feat(eslint-plugin): [no-unnecessary-type-parameters] special case readonly tuples and return location arrays as single-use Jan 7, 2025

JoshuaKGoldberg changed the title ~~feat(eslint-plugin): [no-unnecessary-type-parameters] special case readonly tuples and return location arrays as single-use~~ feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and return location arrays as single-use Jan 7, 2025

JoshuaKGoldberg requested a review from kirkwaiblinger January 7, 2025 14:10

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jfet97 and others added 2 commits January 28, 2025 18:02

implement some suggested changes

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Finally commit docs reverts/touchups

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JoshuaKGoldberg changed the title ~~feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and return location arrays as single-use~~ feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and parameter location arrays as single-use Feb 24, 2025

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Bug: [no-unnecessary-type-parameters] should parenthesize type in suggestion fixer if necessary #10894

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feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and parameter location arrays as single-use #9536

feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and parameter location arrays as single-use #9536

jfet97 commented Jul 10, 2024 •

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feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and parameter location arrays as single-use #9536

feat(eslint-plugin): [no-unnecessary-type-parameters] special case tuples and parameter location arrays as single-use #9536

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