analyzer SERVER_ERROR for allowed_experiments.json: Cannot open file

[Hixie]

I saw the following, probably when switching branches or upgrading Flutter while the analyzer was running:

Error response from the server: SERVER_ERROR
FileSystemException(path=/home/ianh/dev/flutter/bin/cache/dart-sdk/lib/_internal/allowed_experiments.json; message=Cannot open file)
#0      _PhysicalFile.readAsStringSync (package:analyzer/file_system/physical_file_system.dart:158:7)
#1      _OverlayFile.readAsStringSync (package:analyzer/file_system/overlay_file_system.dart:196:18)
#2      FolderBasedDartSdk.allowedExperimentsJson (package:analyzer/src/dart/sdk/sdk.dart:412:10)
#3      FeatureSetProvider._experimentsForSdk (package:analyzer/src/dart/analysis/feature_set_provider.dart:150:34)
#4      FeatureSetProvider.build (package:analyzer/src/dart/analysis/feature_set_provider.dart:137:30)
#5      AnalysisDriver._createFileTracker (package:analyzer/src/dart/analysis/driver.dart:1469:45)
#6      new AnalysisDriver (package:analyzer/src/dart/analysis/driver.dart:291:5)
#7      ContextBuilderImpl.createContext (package:analyzer/src/dart/analysis/context_builder.dart:130:18)
#8      new AnalysisContextCollectionImpl (package:analyzer/src/dart/analysis/analysis_context_collection.dart:93:36)
#9      ContextManagerImpl._createAnalysisContexts.performContextRebuildGuarded.performContextRebuild
(package:analysis_server/src/context_manager.dart:463:40)
<asynchronous suspension>
#10     ContextManagerImpl._createAnalysisContexts.performContextRebuildGuarded (package:analysis_server/src/context_manager.dart:606:11)
<asynchronous suspension>

[bwilkerson]

@scheglov

[Hixie]

Got a more serious one today (unfortunately I accidentally blew away the console before I could copy the stack) where it actually crashed the analyzer entirely. Looks like the analyzer in general is very sensitive to sudden filesystem changes of the kind you see when switching git branches.

[Hixie]

Steps to reproduce are something like this:

0. Run ulimit -Sn unlimited.
1. Check out flutter's master branch.
2. In the flutter repo, run flutter update-packages; flutter analyze --watch --write /tmp/analysis --flutter-repo
3. Change to a branch with a different version of the engine, e.g. flutter channel stable or the equivalent with git.
4. Run flutter doctor -v or flutter upgrade or flutter test or similar to cause it to download the different Dart.

The analyzer suddenly throws the exception above.