Fix TextInput isFocused false positive on stale refs after unmount

[chicio]

Summary:

This PR fixes a false positive in in the TextInput component in the isFocused method.

Before the modification I made in this PR, the isFocused was (wrongly) returning true if both TextInputState.currentlyFocusedInput() and inputRef.current (in TextInput) were null. This can happen eg. when a TextInput is never focused and a stale ref is checked after unmount.

This fix adds an explicit not null check for TextInputState.currentlyFocusedInput(). I also added some tests to cover the unmount scenarios, including:

• unmounted after being focused
• unmounted and never focused (demonstrating the issue described above and in the TODO I removed)

Changelog:

[GENERAL] [FIXED] - Fixed isFocused false positive

Test Plan:

• Ran TextInput-itest.js fantom test and verify all tests cases passed (yarn fantom TextInput-itest)
  • Added additional tests to simulate false positives and missing scenarios (all connected to unmount)
• Ran the full React Native test suite to ensure all tests pass.

[meta-codesync]

@NickGerleman has imported this pull request. If you are a Meta employee, you can view this in D94076114.

[chicio]

Hi @NickGerleman , thank you so much for importing my PR! 🙏
Let me know if I have to do anything else for this one.

[react-native-bot]

This pull request was successfully merged by @chicio in 42cd0f0

^{When will my fix make it into a release? | How to file a pick request?}

[meta-codesync]

@NickGerleman merged this pull request in 42cd0f0.