This PR tackles#3440 and makes the rule skip cases where the type assertion is necessary and auto-fixing to usingreduce()'s type parameter will result in a type error.

Alternatively, as code that does this isn't exactly safe, the rule can still report such cases but use a suggestion instead of an auto-fix (althoughno-unsafe-type-assertion will report the assertion as unsafe).

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ronami commented

Dec 13, 2024

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packages/eslint-plugin/tests/rules/prefer-reduce-type-parameter.test.ts

Comment on lines +83 to +91

		function f<T extends Record<string, boolean>>() {
		['a', 'b'].reduce(
		(accum, name) => ({
		...accum,
		[name]: true,
		}),
		{} as T,
		);
		}

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ronamiDec 13, 2024

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This was a missing edge case in#10453.

ronami commented

Dec 13, 2024

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packages/eslint-plugin/tests/rules/prefer-reduce-type-parameter.test.ts

Comment on lines +72 to +78

		['a', 'b'].reduce(
		(accum, name) => ({
		...accum,
		[name]: true,
		}),
		{ a: true, b: false, c: true } as Record<'a' \| 'b', boolean>,
		);

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ronamiDec 13, 2024•
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I'm not sure if it's necessary to cover this, but it's somewhat ofan edge case with TypeScript's assignability.

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Heh, yeah, I say let's cover it.

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codecovbot commentedDec 13, 2024•
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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.78%. Comparing base(a383d50) to head(505f513).

❗Current head505f513 differs from pull request most recent head906407e
Pleaseupload reports for the commit906407e to get more accurate results.

Additional details and impacted files

@@           Coverage Diff           @@##             main   #10494   +/-   ##=======================================  Coverage   86.78%   86.78%           =======================================  Files         445      445             Lines       15356    15363    +7       Branches     4472     4474    +2     =======================================+ Hits        13326    13333    +7  Misses       1675     1675             Partials      355      355

Flag	Coverage Δ
unittest	`86.78% <100.00%> (+<0.01%)`	⬆️

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

Files with missing lines	Coverage Δ
...t-plugin/src/rules/prefer-reduce-type-parameter.ts	`100.00% <100.00%> (ø)`

ronami marked this pull request as ready for review

December 13, 2024 10:01

ronami marked this pull request as draft

December 13, 2024 10:01

cover a missing test

525a109

ronami commented

Dec 13, 2024

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packages/eslint-plugin/tests/rules/prefer-reduce-type-parameter.test.ts

		}
		`,
		`
		['a', 'b'].reduce((accum, name) => \`\${accum} \| hello \${name}!\`);

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ronamiDec 13, 2024•
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This isn't directly related to the change, but it was previously missing coverage, and because it is on its own line now, it fails codecov.

ronami marked this pull request as ready for review

December 13, 2024 10:29

ronami added2 commits

December 13, 2024 13:05

Merge branch 'main' into prefer-reduce-type-parameter-unfixable-repor…

505f513

…ting

change comment wording

906407e

JoshuaKGoldberg approved these changes

Dec 14, 2024

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YES FINALLY!!!!

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

Dec 14, 2024

JoshuaKGoldberg merged commitba39dde intotypescript-eslint:main

Dec 21, 2024

62 checks passed

ronami deleted the prefer-reduce-type-parameter-unfixable-reporting branch

December 21, 2024 14:09

renovatebot added a commit to andrei-picus-tink/auto-renovate that referenced this pull request

Dec 23, 2024

Update typescript-eslint monorepo to v8.18.2

1e3f82f

| datasource | package                          | from   | to     || ---------- | -------------------------------- | ------ | ------ || npm        | @typescript-eslint/eslint-plugin | 8.18.1 | 8.18.2 || npm        | @typescript-eslint/parser        | 8.18.1 | 8.18.2 |## [v8.18.2](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8182-2024-12-23)##### 🩹 Fixes-   **eslint-plugin:** \[no-unnecessary-condition] handle noUncheckedIndexedAccess true ([#10514](typescript-eslint/typescript-eslint#10514))-   **eslint-plugin:** \[consistent-type-assertions] allow default assertionStyle option ([#10512](typescript-eslint/typescript-eslint#10512))-   **eslint-plugin:** \[no-unnecessary-type-arguments] handle type/value context ([#10503](typescript-eslint/typescript-eslint#10503))-   **eslint-plugin:** \[no-unsafe-type-assertion] fix for unsafe assertion to a constrained type parameter ([#10461](typescript-eslint/typescript-eslint#10461))-   **eslint-plugin:** \[consistent-indexed-object-style] use a suggestion over an auto-fix if can't reliably determine that produced index signature is valid ([#10490](typescript-eslint/typescript-eslint#10490))-   **eslint-plugin:** \[no-unnecessary-condition] don't flag values of an unconstrained or valid type parameter ([#10473](typescript-eslint/typescript-eslint#10473))-   **eslint-plugin:** \[prefer-reduce-type-parameter] don't report cases in which the fix results in a type error ([#10494](typescript-eslint/typescript-eslint#10494))-   **eslint-plugin:** \[no-deprecated] not reporting usages of deprecated declared constants as object value ([#10498](typescript-eslint/typescript-eslint#10498))##### ❤️ Thank You-   Luke Deen Taylor [@controversial](https://github.com/controversial)-   Ronen Amiel-   Scott O'Hara-   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.

renovatebot added a commit to mmkal/eslint-plugin-mmkal that referenced this pull request

Dec 23, 2024

fix(deps): update typescript-eslint monorepo to v8.18.2

5f8d091

##### [v8.18.2](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8182-2024-12-23)##### 🩹 Fixes-   **eslint-plugin:** \[no-unnecessary-condition] handle noUncheckedIndexedAccess true ([#10514](typescript-eslint/typescript-eslint#10514))-   **eslint-plugin:** \[consistent-type-assertions] allow default assertionStyle option ([#10512](typescript-eslint/typescript-eslint#10512))-   **eslint-plugin:** \[no-unnecessary-type-arguments] handle type/value context ([#10503](typescript-eslint/typescript-eslint#10503))-   **eslint-plugin:** \[no-unsafe-type-assertion] fix for unsafe assertion to a constrained type parameter ([#10461](typescript-eslint/typescript-eslint#10461))-   **eslint-plugin:** \[consistent-indexed-object-style] use a suggestion over an auto-fix if can't reliably determine that produced index signature is valid ([#10490](typescript-eslint/typescript-eslint#10490))-   **eslint-plugin:** \[no-unnecessary-condition] don't flag values of an unconstrained or valid type parameter ([#10473](typescript-eslint/typescript-eslint#10473))-   **eslint-plugin:** \[prefer-reduce-type-parameter] don't report cases in which the fix results in a type error ([#10494](typescript-eslint/typescript-eslint#10494))-   **eslint-plugin:** \[no-deprecated] not reporting usages of deprecated declared constants as object value ([#10498](typescript-eslint/typescript-eslint#10498))##### ❤️ Thank You-   Luke Deen Taylor [@controversial](https://github.com/controversial)-   Ronen Amiel-   Scott O'Hara-   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.

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Dec 30, 2024

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fix(eslint-plugin): [prefer-reduce-type-parameter] don't report cases in which the fix results in a type error#10494

fix(eslint-plugin): [prefer-reduce-type-parameter] don't report cases in which the fix results in a type error#10494

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