[Tool] Handle DTD connection failures gracefully in widget-preview#186952
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Previously, unhandled RpcExceptions and connection-closed StateErrors bubbled up and crashed the "flutter widget-preview start" command and the active file-watching sync streams when the Dart Tooling Daemon (DTD) connection was closed unexpectedly. This change: - Wraps startup DTD calls in a try-catch block and throws a user-friendly ToolExit on failure instead of crashing. - Gracefully catches DTD call exceptions inside the file-watcher stream and logs a warning instead of crashing the active stream. - Adds a unit test case in widget_preview_test.dart to verify that DTD communication failures at startup result in a clean ToolExit.
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This pull request improves error handling for the Dart Tooling Daemon (DTD) by catching exceptions during widget preview retrieval and logging warnings upon connection loss. Feedback suggests that the try-catch block in widget_preview.dart should also catch StateError to prevent crashes, as StateError does not inherit from Exception. Additionally, a redundant type check for RpcException in lsp_preview_detector.dart was identified for simplification.
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| } on Exception catch (e) { | ||
| throwToolExit( | ||
| 'Failed to retrieve widget previews from the Dart Tooling Daemon (DTD). ' | ||
| 'Ensure that the analysis server is running and reachable. Details: $e', | ||
| ); | ||
| } |
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The PR description mentions that StateError (specifically connection-closed) was causing crashes. However, this try-catch block only catches Exception. Since StateError is a subclass of Error, not Exception, it will still bubble up and cause a crash here. Consider catching both Exception and StateError to ensure graceful handling as intended.
} catch (e) {\n if (e is! Exception && e is! StateError) {\n rethrow;\n }\n throwToolExit(\n 'Failed to retrieve widget previews from the Dart Tooling Daemon (DTD). '\n 'Ensure that the analysis server is running and reachable. Details: $e',\n );\n }| } catch (e) { | ||
| if (_disposed || shutdownHooks.isShuttingDown) { | ||
| logger.printTrace('Failed to get widget previews during shutdown: $e'); | ||
| } else if (e is RpcException || e is StateError || e is Exception) { |
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The check e is RpcException is redundant because RpcException is a subclass of Exception, which is already included in the condition. This can be simplified to improve readability.
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| } else if (e is RpcException || e is StateError || e is Exception) { | |
| } else if (e is StateError || e is Exception) { |
References
- Suggest simplification and refactoring to enhance readability and maintainability. (link)
- Catch StateError in addition to Exception during widget-preview startup to prevent crashes. - Remove redundant RpcException check and unused import in lsp_preview_detector.dart. TAG=agy CONV=bd211533-a25a-4fe2-afbc-c14902fc9bca
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An existing Git SHA, To re-trigger presubmits after closing or re-opeing a PR, or pushing a HEAD commit (i.e. with |
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An existing Git SHA, To re-trigger presubmits after closing or re-opeing a PR, or pushing a HEAD commit (i.e. with |
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May 25, 2026
This was referenced May 26, 2026
This was referenced May 26, 2026
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Previously, unhandled RpcExceptions and connection-closed StateErrors bubbled up and crashed the "flutter widget-preview start" command and the active file-watching sync streams when the Dart Tooling Daemon (DTD) connection was closed unexpectedly.
This change:
Fixes #187322