file.dart test suite failures

[zanderso]

On google/file.dart#56, @tvolkert has noted inconsistencies in test outcomes between Windows and other platforms. I'm mirroring this in the Dart issue tracker so that we don't lose track of it, and to keep more fine-grained notes:

These tests from https://github.com/google/file.dart/blob/master/test/local_test.dart either fail when they should succeed or succeed when they should fail:

• 'FileSystem > currentDirectory > throwsIfHasNonExistentPathInComplexChain',
• 'FileSystem > currentDirectory > staysAtRootIfSetToParentOfRoot',
• 'FileSystem > currentDirectory > resolvesLinksIfEncountered',
• 'FileSystem > currentDirectory > succeedsIfSetToDirectoryLinkAtTail',
• 'FileSystem > stat > isFileForLinkToFile',
• 'FileSystem > type > isFileForLinkToFileAndFollowLinksTrue',
• 'FileSystem > type > isNotFoundForLinkWithCircularReferenceAndFollowLinksTrue',
• 'Directory > uri',
• 'Directory > exists > falseIfExistsAsLinkToFile',
• 'Directory > exists > falseIfNotFoundSegmentExistsThenIsBackedOut',
• 'Directory > create > throwsIfAlreadyExistsAsLinkToFile',
• 'Directory > rename > throwsIfDestinationIsNonEmptyDirectory',
• 'Directory > rename > throwsIfDestinationIsLinkToEmptyDirectory',
• 'Directory > delete > throwsIfPathReferencesLinkToFileAndRecursiveFalse',
• 'Directory > resolveSymbolicLinks > throwsIfPathNotFoundInMiddleThenBackedOut',
• 'Directory > createTemp > succeedsWithNestedPathPrefixThatExists',
• 'Directory > list > followsLinksIfFollowLinksTrue',
• 'Directory > list > returnsLinkObjectsForRecursiveLinkIfFollowLinksTrue',
• 'File > uri',
• 'File > create > succeedsIfAlreadyExistsAsLinkToFile',
• 'File > create > succeedsIfAlreadyExistsAsLinkToNotFoundAtTail',
• 'File > create > succeedsIfAlreadyExistsAsLinkToNotFoundInDifferentDirectory',
• 'File > rename > succeedsIfDestinationExistsAsLinkToFile',
• 'File > rename > succeedsIfDestinationExistsAsLinkToNotFound',
• 'File > rename > succeedsIfSourceExistsAsLinkToFile',
• 'File > copy > succeedsIfDestinationExistsAsLinkToFile',
• 'File > copy > succeedsIfSourceExistsAsLinkToFile',
• 'File > copy > succeedsIfSourceIsLinkToFileInDifferentDirectory',
• 'File > copy > succeedsIfDestinationIsLinkToFileInDifferentDirectory',
• 'File > openRead > succeedsIfExistsAsLinkToFile',
• 'File > openWrite > succeedsIfExistsAsLinkToFile',
• 'File > openWrite > ioSink > throwsIfEncodingIsNullAndWriteObject',
• 'File > openWrite > ioSink > allowsChangingEncoding',
• 'File > openWrite > ioSink > succeedsIfAddRawData',
• 'File > openWrite > ioSink > succeedsIfWrite',
• 'File > openWrite > ioSink > succeedsIfWriteAll',
• 'File > openWrite > ioSink > succeedsIfWriteCharCode',
• 'File > openWrite > ioSink > succeedsIfWriteln',
• 'File > openWrite > ioSink > addStream > succeedsIfStreamProducesData',
• 'File > openWrite > ioSink > addStream > blocksCallToAddWhileStreamIsActive',
• 'File > openWrite > ioSink > addStream > blocksCallToWriteWhileStreamIsActive',
• 'File > openWrite > ioSink > addStream > blocksCallToWriteAllWhileStreamIsActive',
• 'File > openWrite > ioSink > addStream > blocksCallToWriteCharCodeWhileStreamIsActive',
• 'File > openWrite > ioSink > addStream > blocksCallToWritelnWhileStreamIsActive',
• 'File > openWrite > ioSink > addStream > blocksCallToFlushWhileStreamIsActive',
• 'File > readAsBytes > succeedsIfExistsAsLinkToFile',
• 'File > readAsString > succeedsIfExistsAsLinkToFile',
• 'File > writeAsBytes > succeedsIfExistsAsLinkToFile',
• 'File > writeAsString > succeedsIfExistsAsLinkToFile',
• 'File > stat > isFileIfExistsAsLinkToFile',
• 'File > delete > succeedsIfExistsAsLinkToFileAndRecursiveFalse',
• 'Link > uri > whenTargetIsDirectory',
• 'Link > uri > whenTargetIsFile',
• 'Link > uri > whenLinkDoesntExist',
• 'Link > stat > isFileIfTargetIsFile',
• 'Link > stat > isDirectoryIfTargetIsDirectory',
• 'Link > create > succeedsIfLinkDoesntExistViaTraversalAndRecursiveTrue',
• 'Link > rename > returnsCovariantType',
• 'Link > rename > succeedsIfDestinationExistsAsLinkToFile',
• 'Link > rename > throwsIfDestinationExistsAsLinkToDirectory',
• 'Link > rename > succeedsIfDestinationExistsAsLinkToNotFound',

[tvolkert]

either fail when they should succeed or succeed when they should fail

... or return an unexpected value (e.g. when we expect true from exists(), but the result is false)

[goderbauer]

We have the first report from a Flutter user who was experiencing a crash on Windows, which was most likely caused by resolveSymbolicLinks not working properly on Windows (see flutter/flutter#8882).

[bkonyi]

I've started looking at some of these in my spare time. I have a feeling some of these tests are failing solely due to differences in behavior between how Windows and other OSes do things. For example, FileSystem > currentDirectory > throwsIfHasNonExistentPathInComplexChain is failing on Windows since cd invalid_dir/../valid_dir will change directory to valid_dir on Windows but fail on Linux. In those cases, we don't intend to try and artificially match behavior between platforms, right?

[bkonyi]

I don't foresee myself having the bandwidth to look at this any time in the near future, so I'm going to unassign myself.

[Xiphoseer]

I just dug into possibly related problem, because I had issues with a build_runner builder / glob pattern not traversing a symlink. I posted some of my findings in PowerShell/PowerShell#15235 (comment). The bottom line is that

sdk/runtime/bin/directory_win.cc

Lines 112 to 114 in 7f85661

	CreateFileW(listing->path_buffer().AsStringW(), 0,
	FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
	NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);

fails on symlinks to directories that were not created with SYMBOLIC_LINK_FLAG_DIRECTORY.

Specifically, this could be a source for #45981