Allow target platform override teardown in widget tests - #186604

Thanks for taking a look. But I don't think this is the correct way. The fundamental problem is that tearDown occurs after the check, against people's expectation. This flag is not the only victim.
I'm not sure how feasible it would be, but I think the correct way to solve this problem is to check the invariants after tearDown.

Thanks, that makes sense. I updated the PR in 114c487 to follow that direction: testWidgets now defers the full Flutter invariant check until after user addTearDown callbacks and before postTest, rather than special-casing debugDefaultTargetPlatformOverride. Direct binding.runTest callers keep immediate invariant verification unless they explicitly opt into the deferred hook.

I also broadened the regression to cover another foundation debug variable (debugDoublePrecision) so the test is no longer target-platform-only.

Verification:

• ./bin/flutter test packages/flutter_test/test/bindings_invariants_test.dart passed
• ./bin/flutter test packages/flutter_test/test/widget_tester_test.dart passed
• ./bin/flutter test packages/flutter_test/test/event_simulation_test.dart --plain-name "debugKeyEventSimulatorTransitModeOverride overrides default transit mode" passed
• ./bin/flutter analyze packages/flutter/lib/src/foundation/debug.dart packages/flutter_test/lib/src/binding.dart packages/flutter_test/lib/src/widget_tester.dart packages/flutter_test/test/bindings_invariants_test.dart passed
• ./bin/dart format --output=none --set-exit-if-changed packages/flutter/lib/src/foundation/debug.dart packages/flutter_test/lib/src/binding.dart packages/flutter_test/lib/src/widget_tester.dart packages/flutter_test/test/bindings_invariants_test.dart passed
• git diff --check passed

Clarified this in e2cc32e: testWidgets can defer because it owns the package:test tearDown callbacks, while lower-level binding.runTest callers keep the immediate invariant check before postTest.

Local verification:

• ./bin/dart format --output=none --set-exit-if-changed packages/flutter_test/lib/src/binding.dart packages/flutter_test/lib/src/widget_tester.dart
• ./bin/dart analyze packages/flutter_test/lib/src/binding.dart packages/flutter_test/lib/src/widget_tester.dart
• git diff --check

The targeted flutter test commands are currently blocked locally by root package resolution: _flutter_packages depends on webview_flutter_wkwebview 3.26.0, which requires Flutter >=3.44.0, while this checkout reports 3.44.0-1.0.pre-1099.

Follow-up: I was able to rerun the focused tests with --no-pub. bindings_invariants_test.dart, widget_tester_test.dart, and the focused event_simulation_test.dart case all passed locally.

Rebased onto current master at 7604d01f45 with no conflicts; the focused regression suites remain green. The fork account cannot restore the CICD label, so a maintainer may need to start presubmits.

Thank you for your work on this PR and for helping identify the issue.

When reviewing the implementation, I found that completely and correctly handling this behavior required a substantially more complex approach across the test binding lifecycle. The solution ultimately took quite a bit of refactoring and debugging to land cleanly, so I ended up rewriting the fix, which has now been merged in #193476.

Because the underlying problem is now resolved on master, I am going to close this PR. Thanks again for your time and contribution here!