Re-copy the prefab headers when a header changes

[YevheniiKotyrlo]

Summary:

PreparePrefabHeadersTask copies ReactAndroid's public headers into build/prefab-headers, the prefab package an app's appmodules and every library's C++ compile against, while libreactnative.so compiles against ReactCommon directly. The task's only input is the list of directory paths:

  @get:Input abstract val input: ListProperty<PrefabPreprocessingEntry>

so after a header under those directories changes, Gradle finds the task up to date and the prefab package keeps the old header. Everything built against the prefab package then disagrees with libreactnative.so about that header: a struct that gained a field is allocated at its old size by a library and used at its new size by React Native.

A header changes in place whenever React Native is built from source and patched with patch-package, or while ReactCommon is edited during development. In an app built from source, a patch that added two fields to Yoga's CachedMeasurement left prefab-headers/reactnative/yoga/node/CachedMeasurement.h, LayoutResults.h, Node.h and style/Style.h at their old content across two builds, and the app crashed at launch with SIGSEGV under YogaLayoutableShadowNode::replaceChild ← cloneChildInPlace ← configureYogaTree.

The task now declares the headers it copies as @InputFiles, read through the same filtered file trees the copy uses, so the declared inputs and the copied headers cannot disagree. Each library's folder is deleted before it is copied into, so a header removed from ReactCommon leaves no copy behind once the task runs again.

Changelog:

[ANDROID] [FIXED] - Re-copy the prefab headers when a header under ReactCommon changes

Test Plan:

• PreparePrefabHeadersTaskTest gains preparePrefabHeadersTask_declaresTheHeadersItCopiesAsInputs (the task's input files are exactly the copied header, not the .cpp beside it) and preparePrefabHeadersTask_withARemovedHeader_removesItsCopy. On main both fail: the input files are [], and removed.h is still in the output after the second run. With the change, all 10 cases pass.
• ./gradlew build -PenableWarningsAsErrors=true in packages/gradle-plugin, in reactnativecommunity/react-native-android:latest: 238 tests, 0 failures. ktfmt 0.59.0 (--dry-run --set-exit-if-changed) is clean on both files.
• In the app above, with the change applied to its @react-native/gradle-plugin: the next build ran preparePrefab instead of finding it up to date, every Yoga header in prefab-headers and in the debug prefab package matched ReactCommon, every library recompiled against them, and the app launched without the crash.

[meta-codesync]

@cortinico has imported this pull request. If you are a Meta employee, you can view this in D125650684.

[meta-codesync]

@cortinico merged this pull request in bf4fac3.