[FileSystem] Bug: Caching IFileInfo, recreating it, will result in stale cache

[pw-sgr]

I've recreated the Microsoft.Extensions.FileProviders.PhysicalFileProvider and use IFileSystem instead of System.IO to mock my service.
To ensure my classes work exactly like the PhysicalFileProvider I also copied the tests. One of the tests fails using the MockFileSystem, but not using the real FileSystem.

Test: UsePollingFileWatcher_UseActivePolling_HasChanged_SymbolicLink_TargetChanged for linkWasBroken is true.

The test with linkWasBroken is false only succeed because it reads file1Path instead of file2Path and file1Path is created, so it's a false positive.

This happens because in the (Custom|Physical)PollingFileChangeToken the (I)FileInfo is cached and only refreshed using the method Refresh().

Afaik this happens because the mocked FileInfo is detached from the storage and thus not updated.

Actual Behavior: detached FileInfo is not updated

Expected Behavior: detached FileInfo is reattached and updated

Possible Solution: Inside IFileInfo.Refresh() check the file system if the file is there and copy the infos

[vbreuss]

I tried to write a failing test, but your example has many dependencies (and the test written by Copilot always succeeded).
Could you help me reproducing it, @pw-sgr?

[pw-sgr]

@vbreuss I'll create an example on monday

[pw-sgr]

@vbreuss the error was on my end.

Due to the bug #812 I created two links. So that I can get the file using link2. What I failed to notice is I deleted helper link link2 and recreated it to point to the second file, I should've deleted link1 and recreated it. With that link2 return for ResolveLinkTarget(true) was null