8368165: (fs) Path.toRealPath does not perform correctly for symbolic links in a mapped drive (win)

[bplb]

If getFinalPath throws an exception, or converts a drive path to a UNC path, then fall back to the slow path which uses resolveAllLinks.

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Issue

• JDK-8368165: (fs) Path.toRealPath does not perform correctly for symbolic links in a mapped drive (win) (Bug - P4)

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[bplb]

This change was tested successfully with links and files on a local mapped disk and on remote shares on macOS and Windows machines.

It might be that falling back to the slow path should be limited to a certain subset of error codes encountered by GetFinalPathNameByHandle rather than falling back for all exceptions.

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[mlbridge]

Webrevs

• 00: Full (8aacdcc6)

[AlanBateman]

toRealPath is specified to throw if it fails. The error FileSystemException: Z:\link: The name of the file cannot be resolved by the system seems okay. So I'm not yet convinced we need to change anything.

[bplb]

I don't think the current behavior is incorrect, but it does not provide the sought for outcome. The fallback path using resolveAllLinks appears to find the desired answer in these cases where GetFinalPathNameByHandle itself fails.

[AlanBateman]

I don't think the current behavior is incorrect, but it does not provide the sought for outcome. The fallback path using resolveAllLinks appears to find the desired answer in these cases where GetFinalPathNameByHandle itself fails.

We can't fallback unconditionally when GetFinalPathNameByHandle fails. The only reason for this fallback path is for cases where there is a sym link to something that we know doesn't support links. So this is why it is limited to ERROR_INVALID_LEVEL, and even then it is dubious and maybe we need to explore the errors and interop issues further before seeing if anything should be done.

[bplb]

We can't fallback unconditionally when GetFinalPathNameByHandle fails.

Right, I was uncertain about this which is why I commented above that "It might be that falling back to the slow path should be limited to a certain subset of error codes".