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Add tests for the PlatformColor lazy color fallback (#57708) - #57708

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Add tests for the PlatformColor lazy color fallback (#57708)#57708
Abbondanzo wants to merge 3 commits into
react:mainfrom
Abbondanzo:export-D111917092

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@Abbondanzo Abbondanzo commented Jul 27, 2026

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Summary:

An implementation for the RFC in react-native-community/discussions-and-proposals#1008

Adds unit and integration coverage for the PlatformColor raw-color fallback introduced in the parent diff:

  • CSSColorTest.cpp: additional CSS <color> parse cases pinning the shared parser used on the native fallback path
  • PlatformColorFallback-itest.js: JS integration test for token-miss -> fallback

Changelog: [Internal]

Reviewed By: christophpurrer

Differential Revision: D111917092

@meta-cla meta-cla Bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label Jul 27, 2026
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meta-codesync Bot commented Jul 27, 2026

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@Abbondanzo has exported this pull request. If you are a Meta employee, you can view the originating Diff in D111917092.

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Warning

JavaScript API change detected

This PR commits an update to ReactNativeApi.d.ts, indicating a change to React Native's public JavaScript API.

  • Please include a clear changelog message.
  • This change will be subject to additional review.

This change was flagged as: POTENTIALLY_BREAKING

Summary:

An implementation for the RFC in react-native-community/discussions-and-proposals#1008

`PlatformColor` previously had no way to specify what color to use when none of the supplied native color tokens resolve on the device. On a miss the behavior was inconsistent across platforms and architectures (transparent, nil, or a thrown error), giving apps no control over the rendered result.

This adds an optional trailing `{fallback: '<raw color string>'}` argument to `PlatformColor(...)` and updates the JS entry points to emit it. The fallback is carried lazily to native as a raw, unprocessed string and is only parsed when every provided token fails to resolve (the native side of that behavior landed earlier in this stack). When at least one token resolves the fallback is ignored, so existing call sites are completely unaffected and omitting the argument preserves today's exact behavior.

Example:

  PlatformColor('someSystemToken', {fallback: '#FF0000'})

Each platform entry point (`PlatformColorValueTypes.{android,ios,macos,windows}.js`, plus the vendored macOS/Windows copies) collects the leading string tokens and, when a trailing `{fallback}` object is present, attaches its raw string to the native color object. Non-string arguments in a non-trailing position are filtered out consistently rather than being forwarded to native. The Flow (`.js.flow`), TypeScript (`.d.ts`), and generated (`ReactNativeApi.d.ts`) declarations widen the signature to `Array<string | {fallback: string}>`, which is backward compatible.

Changelog:
[General][Added] - Support a lazy raw color fallback for PlatformColor when native tokens fail to resolve

Reviewed By: javache, huntie

Differential Revision: D113329139
Summary:

An implementation for the RFC in react-native-community/discussions-and-proposals#1008

Rounds out the lazy `PlatformColor` fallback with tooling and a demo.

- The `react-native/platform-colors` ESLint rule now permits an optional trailing `{fallback: <literal>}` options object so `PlatformColor('token', {fallback: '#RRGGBB'})` is lint-clean, while still requiring every other argument to be a literal. The options object must have exactly one `fallback` property whose value is a literal, so it stays statically analyzable.
- A new "Lazy Fallback Colors" section in the RNTester `PlatformColor` example demonstrates valid tokens, misses with no fallback (transparent), and misses with hex / `rgb()` / `rgba()` / `#RRGGBBAA` fallbacks across `backgroundColor`, text `color`, and `borderColor`.

Changelog:
[Internal] - PlatformColor: ESLint support and RNTester example for the lazy raw-color fallback

Reviewed By: christophpurrer

Differential Revision: D113329138
Summary:

An implementation for the RFC in react-native-community/discussions-and-proposals#1008

Adds unit and integration coverage for the PlatformColor raw-color fallback introduced in the parent diff:
- CSSColorTest.cpp: additional CSS `<color>` parse cases pinning the shared parser used on the native fallback path
- PlatformColorFallback-itest.js: JS integration test for token-miss -> fallback

Changelog: [Internal]

Reviewed By: christophpurrer

Differential Revision: D111917092
@meta-codesync meta-codesync Bot changed the title Add tests for the PlatformColor lazy color fallback Add tests for the PlatformColor lazy color fallback (#57708) Aug 5, 2026
@meta-codesync meta-codesync Bot closed this in 85e07db Aug 6, 2026
@meta-codesync meta-codesync Bot added the Merged This PR has been merged. label Aug 6, 2026
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meta-codesync Bot commented Aug 6, 2026

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This pull request has been merged in 85e07db.

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