[compiler] Fix invariant error for optional chaining in try/catch

[everettbu]

Mirror of facebook/react#35573
Original author: josephsavona

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Optional chaining and other value blocks within try/catch blocks were throwing an Invariant error ("Unexpected terminal in optional") instead of the expected Todo error. This caused hard failures instead of graceful bailouts.

The issue occurred because DropManualMemoization and ValidateExhaustiveDependencies ran before BuildReactiveFunction, and encountered maybe-throw terminals in their switch statements without a handler, falling through to the invariant case.

Fixed by adding explicit maybe-throw cases in both files that throw the proper Todo error with the message "Support value blocks (conditional, logical, optional chaining, etc) within a try/catch statement".

Also renamed the existing bug test to reflect it's now correctly handled:

• error.bug-invariant-unexpected-terminal-in-optional → error.todo-optional-chaining-within-try-catch

Closes #35570

---

Stack created with Sapling. Best reviewed with ReviewStack.

• #35607
• #35298
• #35596
• -> #35573
• #35595
• #35539

[greptile-apps]

Greptile Summary

Fixed invariant error when optional chaining appears within try/catch blocks by adding explicit maybe-throw terminal handlers in DropManualMemoization and ValidateExhaustiveDependencies that throw proper Todo errors instead of falling through to invariant cases.

• Added maybe-throw case handlers in two compiler passes that run before BuildReactiveFunction
• Renamed test from error.bug-invariant-unexpected-terminal-in-optional to error.todo-optional-chaining-within-try-catch to reflect the corrected behavior
• Added new test case for optional chaining within try/catch in async callbacks
• Included comprehensive documentation for all 55 compiler passes to help with future development
• Enhanced snap test runner with fixture status tracking for better debugging workflow

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The fix is straightforward and surgical - adds explicit error handling for a specific terminal type in two switch statements. The changes are well-tested with both existing and new test cases confirming proper error behavior. The documentation additions are supplementary improvements that don't affect runtime behavior.
• No files require special attention

Important Files Changed

Filename	Overview
compiler/packages/babel-plugin-react-compiler/src/Inference/DropManualMemoization.ts	Added maybe-throw case to handle optional chaining in try/catch, throwing proper Todo error instead of invariant
compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateExhaustiveDependencies.ts	Added maybe-throw case to handle optional chaining in try/catch, throwing proper Todo error instead of invariant
compiler/packages/babel-plugin-react-compiler/src/tests/fixtures/compiler/error.todo-optional-chaining-within-try-catch.js	Renamed test from error.bug-invariant-unexpected-terminal-in-optional to reflect correct Todo error behavior
compiler/packages/babel-plugin-react-compiler/src/tests/fixtures/compiler/error.todo-optional-chaining-within-try-catch-in-callback.js	Added new test case for optional chaining within try/catch in async callback
compiler/packages/snap/src/runner.ts	Added fixture status tracking for autocomplete suggestions in watch mode

[greptile-apps]

Additional Comments (1)

1. compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.bug-invariant-unexpected-terminal-in-optional.expect.md, line 22 (link)

   logic: test expectation file should be updated to reflect the new Todo error instead of the Invariant error

   the PR description states the test was renamed from error.bug-invariant-unexpected-terminal-in-optional to error.todo-optional-chaining-within-try-catch and the expectation should now show a Todo error with message "Support value blocks (conditional, logical, optional chaining, etc) within a try/catch statement" instead of the invariant error shown here

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[greptile-apps]

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[greptile-apps]

style: missing break statement after throwTodo() - while this doesn't cause issues since throwTodo never returns, adding a break would follow switch case best practices and improve code clarity

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

Prompt To Fix With AI

This is a comment left during a code review.
Path: compiler/packages/babel-plugin-react-compiler/src/Inference/DropManualMemoization.ts
Line: 586:593

Comment:
**style:** missing `break` statement after `throwTodo()` - while this doesn't cause issues since `throwTodo` never returns, adding a `break` would follow switch case best practices and improve code clarity

<sub>Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!</sub>

How can I resolve this? If you propose a fix, please make it concise.

[greptile-apps]

style: missing break statement after throwTodo() - while this doesn't cause issues since throwTodo never returns, adding a break would follow switch case best practices and improve code clarity

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

Prompt To Fix With AI

This is a comment left during a code review.
Path: compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateExhaustiveDependencies.ts
Line: 1019:1026

Comment:
**style:** missing `break` statement after `throwTodo()` - while this doesn't cause issues since `throwTodo` never returns, adding a `break` would follow switch case best practices and improve code clarity

<sub>Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!</sub>

How can I resolve this? If you propose a fix, please make it concise.