tmpdir names get too long on Windows (exceeding PATH_MAX)

[pytestbot]

Originally reported by: Torsten Landschoff (BitBucket: bluehorn, GitHub: bluehorn)

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Hi pytest Team,

we run into a lot of error in our release tests lately, which do not occur in nightly an on-commit tests. Looking into this, I discovered that path names get too long when we are using tmpdir:

c:\users\dynamore\appdata\local\temp\pytest-21\test_change_own_private_components_public_incoming_conflict_pull_C__jenkins_workspace_loco2_win7_32_client_release_testdata_testdb_dump_0\vaultdir\zipped\00\005292e500e4e76be18e798eccee423dec2e24c57db4b030348e67a7

On (german) Windows this results into

WindowsError: [Error 3] Das System kann den angegebenen Pfad nicht finden

which would point to a bug in our implementation.

It is unobvious to me that tmpdir includes the following info in the path:

• the full function name
• the parameters of the test call (full path to testdb.dump over here)

This can make the temporary path arbitrary long which causes problems on Windows. I think, py.test should shorten the path automatically (at least on Windows). We can work around this by passing relative filenames (less robust in case the code does a chdir, but that would break other tests anyway) and by shorting the names of our test functions. However, I would like to keep the test function names expressive.

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• Bitbucket: https://bitbucket.org/pytest-dev/pytest/issue/291

[pytestbot]

Original comment by holger krekel (BitBucket: hpk42, GitHub: hpk42):

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tmpdir should grow more intelligent about constructing its name, agreed. up for a patch? (_pytest/tmpdir.py and testing/test_tmpdir.py are affected i think).

[pytestbot]

Original comment by Nenad Ognjanovic (BitBucket: bgr_, GitHub: bgr_):

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Hi,
I've managed to overcome the limit on Windows by prefixing the path with \\?\ (as specified here). What do you think about this approach (and do you think it would be the right thing to integrate this workaround in py.path instead, since it looks like it fits there)?

[nicoddemus]

This has been fixed for awhile now, tmpdir automatically truncates directory names to around 30 chars:

def test_tmpdir_test_change_own_private_components_public_incoming_conflict_pull_C__jenkins_workspace_loco2_win7_32_client_release_testdata_testdb_dump(tmpdir):
    print(tmpdir)
    assert 0 

Generates this path:

C:\Users\Bruno\AppData\Local\Temp\pytest-of-Bruno\pytest-173\test_tmpdir_test_change_own_pr0

So I'm closing this. 😄

cc @Bluehorn

[Bluehorn]

Agreed, looks fixed to me :-)