fix(eslint-plugin): [prefer-nullish-coalescing] treat `any`/`unknown` as eligible for nullish coalescing #10865

kirkwaiblinger · 2025-02-21T23:08:55Z

PR Checklist

Addresses an existing open issue: fixes Enhancement: [prefer-nullish-coalescing] revisit considering any/unknown possibly-nullish #10694
That issue was marked as accepting prs
Steps in Contributing were taken

Overview

Rather than creating a separate "ignorePrimitives"-like option for any/unknown, I interpreted it that any/unknown will only be eligible for conversion if all "ignorePrimitive" options are false, since that matches the assignability.

Also, I

moved the isPossiblyNullish utility back to no-unnecessary-condition since it differs from isNullableType, and isNullableType is more reliable.
Fixed some examples on the docs page that this change exposed

cc @OlivierZal

typescript-eslint · 2025-02-21T23:08:59Z

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codecov · 2025-02-21T23:54:39Z

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.48%. Comparing base (7f2a5bd) to head (bea323d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10865   +/-   ##
=======================================
  Coverage   87.48%   87.48%           
=======================================
  Files         469      469           
  Lines       16089    16089           
  Branches     4666     4667    +1     
=======================================
  Hits        14075    14075           
  Misses       1658     1658           
  Partials      356      356

Flag	Coverage Δ
unittest	`87.48% <100.00%> (ø)`

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

Files with missing lines	Coverage Δ
...slint-plugin/src/rules/no-unnecessary-condition.ts	`99.21% <100.00%> (+0.01%)`	⬆️
...lint-plugin/src/rules/prefer-nullish-coalescing.ts	`95.65% <100.00%> (+0.07%)`	⬆️
packages/eslint-plugin/src/util/truthinessUtils.ts	`100.00% <ø> (ø)`

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ronami

👍👍 Looking good! Requesting minor changes, mostly around testing.

ronami · 2025-03-01T22:45:27Z

packages/eslint-plugin/src/rules/prefer-nullish-coalescing.ts

+        // won't be set.
+        (tsutils.isTypeFlagSet(
+          type,
+          ts.TypeFlags.Any | ts.TypeFlags.Undefined | ts.TypeFlags.Void,


[Test]: Removing ts.TypeFlags.Void or ts.TypeFlags.Undefined doesn't fail any test. Let's simplify or add a test case?

Touche - undefined was a typo and should have been unknown 😅 . That resolves #10865 (comment). void is a TS error. removed!

packages/eslint-plugin/src/rules/no-unnecessary-condition.ts

ronami · 2025-03-01T22:58:06Z

packages/eslint-plugin/src/rules/prefer-nullish-coalescing.ts

+          .typeParts(type)
+          .some(t =>
+            tsutils
+              .intersectionTypeParts(t)


[Test]: Can this be simplified to use .typeParts() instead of .intersectionTypeParts()? Changing this doesn't seem to fail any test.

Maybe... I think I'd like to leave that line as is since technically it wasn't touched in this PR though. (The change that I had to make was because the type assertion type as ts.UnionOrIntersectionType was no longer valid). It's generally a bit of a smell I think if we treated unions and intersections the same shallowly, but not recursively 🤔 But I don't have a test case in mind

ronami · 2025-03-01T23:12:52Z

packages/eslint-plugin/src/rules/prefer-nullish-coalescing.ts

+        // won't be set.
+        (tsutils.isTypeFlagSet(
+          type,
+          ts.TypeFlags.Any | ts.TypeFlags.Undefined | ts.TypeFlags.Void,


[Bug]: To my understanding, an unknown type with any of the ignorePrimitives options set to true shouldn't be reported (deploy preview playground link):

// ignorePrimitives: /* any set to true */ // passes correctly with `any` declare const u1: any; const foo1 = u1 || 'bar' // should pass with `unknown`? declare const u2: unknown; const foo2 = u2 || 'bar'

good catch! should be fixed now 👍

Co-authored-by: Ronen Amiel <[email protected]>

ronami

👍👍

OlivierZal · 2025-03-03T17:10:30Z

FWIW it also looks good to me 😊

kirkwaiblinger · 2025-03-04T00:50:52Z

had to fix up a nasty merge conflict, but should be good to again! 👍

ronami

🚀🚀🚀

packages/eslint-plugin/tests/rules/prefer-nullish-coalescing.test.ts

Co-authored-by: Ronen Amiel <[email protected]>

… as eligible for nullish coalescing (typescript-eslint#10865) * treat any/unknown as eligible for nullish coalescing * more stuff * fix typo Co-authored-by: Ronen Amiel <[email protected]> * feedback * tweaks * merge mistake * rename vars in test Co-authored-by: Ronen Amiel <[email protected]> --------- Co-authored-by: Ronen Amiel <[email protected]>

@kirkwaiblinger

| datasource | package | from | to | | ---------- | -------------------------------- | ------ | ------ | | npm | @typescript-eslint/eslint-plugin | 8.26.0 | 8.26.1 | | npm | @typescript-eslint/parser | 8.26.0 | 8.26.1 | ## [v8.26.1](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8261-2025-03-10) ##### 🩹 Fixes - **eslint-plugin:** \[no-unsafe-return] handle recursive type ([#10883](typescript-eslint/typescript-eslint#10883)) - **eslint-plugin:** \[prefer-nullish-coalescing] treat `any`/`unknown` as eligible for nullish coalescing ([#10865](typescript-eslint/typescript-eslint#10865)) ##### ❤️ Thank You - Kirk Waiblinger [@kirkwaiblinger](https://github.com/kirkwaiblinger) - 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.

@kirkwaiblinger

| datasource | package | from | to | | ---------- | -------------------------------- | ------ | ------ | | npm | @typescript-eslint/eslint-plugin | 8.26.0 | 8.26.1 | | npm | @typescript-eslint/parser | 8.26.0 | 8.26.1 | ## [v8.26.1](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8261-2025-03-10) ##### 🩹 Fixes - **eslint-plugin:** \[no-unsafe-return] handle recursive type ([#10883](typescript-eslint/typescript-eslint#10883)) - **eslint-plugin:** \[prefer-nullish-coalescing] treat `any`/`unknown` as eligible for nullish coalescing ([#10865](typescript-eslint/typescript-eslint#10865)) ##### ❤️ Thank You - Kirk Waiblinger [@kirkwaiblinger](https://github.com/kirkwaiblinger) - 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.

treat any/unknown as eligible for nullish coalescing

1e04761

more stuff

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ronami requested changes Mar 1, 2025

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ronami added the awaiting response Issues waiting for a reply from the OP or another party label Mar 1, 2025

kirkwaiblinger and others added 2 commits March 3, 2025 00:53

fix typo

b1aa570

Co-authored-by: Ronen Amiel <[email protected]>

feedback

9a39d66

kirkwaiblinger requested a review from ronami March 3, 2025 08:21

github-actions bot removed the awaiting response Issues waiting for a reply from the OP or another party label Mar 3, 2025

tweaks

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ronami previously approved these changes Mar 3, 2025

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ronami added the 1 approval >=1 team member has approved this PR; we're now leaving it open for more reviews before we merge label Mar 3, 2025

Merge branch 'main' into prefer-nullish-coalescing-possibly-nullish

3ca6460

kirkwaiblinger dismissed ronami’s stale review via 3ca6460 March 4, 2025 00:47

merge mistake

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kirkwaiblinger requested a review from ronami March 4, 2025 00:50

github-actions bot removed the 1 approval >=1 team member has approved this PR; we're now leaving it open for more reviews before we merge label Mar 4, 2025

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ronami added the 1 approval >=1 team member has approved this PR; we're now leaving it open for more reviews before we merge label Mar 5, 2025

rename vars in test

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Co-authored-by: Ronen Amiel <[email protected]>

kirkwaiblinger dismissed ronami’s stale review via f82db50 March 6, 2025 00:50

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github-actions bot removed the 1 approval >=1 team member has approved this PR; we're now leaving it open for more reviews before we merge label Mar 6, 2025

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kirkwaiblinger enabled auto-merge (squash) March 6, 2025 17:02

Merge branch 'main' into prefer-nullish-coalescing-possibly-nullish

bea323d

kirkwaiblinger merged commit dba0bed into typescript-eslint:main Mar 6, 2025
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kirkwaiblinger deleted the prefer-nullish-coalescing-possibly-nullish branch March 28, 2025 19:40

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fix(eslint-plugin): [prefer-nullish-coalescing] treat any/unknown as eligible for nullish coalescing #10865

fix(eslint-plugin): [prefer-nullish-coalescing] treat any/unknown as eligible for nullish coalescing #10865

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fix(eslint-plugin): [prefer-nullish-coalescing] treat `any`/`unknown` as eligible for nullish coalescing #10865

fix(eslint-plugin): [prefer-nullish-coalescing] treat `any`/`unknown` as eligible for nullish coalescing #10865

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