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[flutter_tools] Resolve symlinks and fix flakiness in widget preview tests - #191214
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…tests Resolve symbolic links in `PreviewDetector`'s project root directory and ephemeral directories to ensure consistent path matching. Pass the SDK path to `AnalysisContextCollection` to ensure correct SDK resolution in worktrees. Add a 100ms delay in test helpers before triggering file changes to allow the file watcher to fully initialize. Fixes: flutter#189849
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This pull request updates PreviewDetector to accept Artifacts and configure the AnalysisContextCollection with the engine Dart SDK path. It also resolves symbolic links for the project root and ephemeral directories using a new helper method, and introduces short delays in tests to allow file watchers to initialize. The feedback suggests caching the resolved ephemeral directory paths during initialization to avoid repeated synchronous file system operations on every file watcher event.
…tector Cache resolved ephemeral directory paths during initialization to avoid repeated synchronous disk I/O on each file watcher event.
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preview_detector_graph_test writes a project to the real file system,
watches it, and expects each step's change event in turn. Twice on a Mac
under Bazel the step that restores a file found the previous step's errors
still reported (the Mac tester's run at 458, 11-01; `Mac_arm64
tool_tests_commands` at 546's presubmit, 11-06: "Expected: Set:[] Actual:
Set:[foo.dart, main.dart]" from expectHasNoErrors): a write's second
FSEvents event, analyzed while the file was still invalid, reported under
the next step's expectation. The test's own note anticipates it ("slow on
heavily loaded machines and cause flaky failures"); dev/bots runs the
commands shard one file at a time (forceSingleCore), and the GN builder
was still 2-3% flaky on this family before flutter#191214; under
Bazel eight tests ran beside it on the Mac bot. The next run passed each
time.
The file is `flaky` in commands_shard_hermetic now (Bazel retries it up to
three times, 17 s each) rather than serialized: `exclusive` would put the
nine widget_preview watcher tests on the Mac shard's critical path for an
intermittent failure of one.
chingjun
added a commit
to chingjun/flutter
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Nov 12, 2026
preview_detector_graph_test writes a project to the real file system,
watches it, and expects each step's change event in turn. Twice on a Mac
under Bazel the step that restores a file found the previous step's errors
still reported (the Mac tester's run at 458, 11-01; `Mac_arm64
tool_tests_commands` at 546's presubmit, 11-06: "Expected: Set:[] Actual:
Set:[foo.dart, main.dart]" from expectHasNoErrors): a write's second
FSEvents event, analyzed while the file was still invalid, reported under
the next step's expectation. The test's own note anticipates it ("slow on
heavily loaded machines and cause flaky failures"); dev/bots runs the
commands shard one file at a time (forceSingleCore), and the GN builder
was still 2-3% flaky on this family before flutter#191214; under
Bazel eight tests ran beside it on the Mac bot. The next run passed each
time.
The file is `flaky` in commands_shard_hermetic now (Bazel retries it up to
three times, 17 s each) rather than serialized: `exclusive` would put the
nine widget_preview watcher tests on the Mac shard's critical path for an
intermittent failure of one.
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Description
PreviewDetector's project root directory and ephemeral directories to ensure consistent path matching.AnalysisContextCollectionto ensure correct SDK resolution in worktrees.Related Issues
Fixes #189849
Tests
packages/flutter_tools/test/commands.shard/hermetic/widget_preview/andpackages/flutter_tools/test/commands.shard/permeable/widget_preview/.