'descend' argument in 'walk' method in twisted.python.filepath._PathHelper class doesn't work well

New submission from Markon <None>:

The 'walk' method in the class _PathHelper, located in twisted/python/filepath.py doesn't work according to the 'descend' argument passed.
This is an example:

{{{
>>> import twisted.python.filepath as FP
>>> filep = FP.FilePath("/home/marco/Desktop")
>>> for x in filep.walk(lambda path: not path.islink()):
...     print x
...
FilePath('/home/marco/Desktop')
FilePath('/home/marco/Desktop/amarok.desktop')
[...]
FilePath('/home/marco/Desktop/MyFolder')
FilePath('/home/marco/Desktop/MyFolder/myfile.txt')
[...]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/site-packages/twisted/python/filepath.py", line 214, in walk
    raise LinkError("Cycle in file graph.")
twisted.python.filepath.LinkError: Cycle in file graph.

}}}

In the Desktop directory there's a symlink "Risorse", which points to "/home/marco". So it creates a cycle, ok. But I've specified the descend argument and it shouldn't follow the link.

However, I've also provided a patch, and if I use it, the argument 'descend' is read fine:


{{{
>>> import filepath as FP
>>> filep = FP.FilePath("/home/marco/Desktop")
>>> for x in filep.walk(lambda path: not path.islink()):
...     print x
...
FilePath('/home/marco/Desktop')
FilePath('/home/marco/Desktop/amarok.desktop')
[...]
FilePath('/home/marco/Desktop/MyFolder')
FilePath('/home/marco/Desktop/MyFolder/myfile.txt')
[...]
FilePath('/home/marco/Desktop/Risorse') <<<---- this is the cyclic symlink
[... other files ...]

}}}

I should write the tests, but in the meantime I attach the patch I've written.






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Type     : defect
Component: core
Keywords : 
Priority : high
Nosy     : 
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http://twistedmatrix.com/trac/ticket/3911