collectstatic --link causes IOError when dangling symlink exists

[Diederik van der Boor]

When a symlink file already exists, but it's source was moved/renamed, collectstatic ends with an IOError.

Here is a trackback example:

Linking '/srv/www/virtualenvs/demo.example.org/src/django-filebrowser-no-grappelli-django14/filebrowser/static/filebrowser/js/FB_TinyMCE.js'
Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/srv/www/virtualenvs/demo.example.org/lib/python2.6/site-packages/django/core/management/__init__.py", line 443, in execute_from_command_line
    utility.execute()
  File "/srv/www/virtualenvs/demo.example.org/lib/python2.6/site-packages/django/core/management/__init__.py", line 382, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/srv/www/virtualenvs/demo.example.org/lib/python2.6/site-packages/django/core/management/base.py", line 196, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/srv/www/virtualenvs/demo.example.org/lib/python2.6/site-packages/django/core/management/base.py", line 232, in execute
    output = self.handle(*args, **options)
  File "/srv/www/virtualenvs/demo.example.org/lib/python2.6/site-packages/django/core/management/base.py", line 371, in handle
    return self.handle_noargs(**options)
  File "/srv/www/virtualenvs/demo.example.org/lib/python2.6/site-packages/django/contrib/staticfiles/management/commands/collectstatic.py", line 163, in handle_noargs
    collected = self.collect()
  File "/srv/www/virtualenvs/demo.example.org/lib/python2.6/site-packages/django/contrib/staticfiles/management/commands/collectstatic.py", line 113, in collect
    handler(path, prefixed_path, storage)
  File "/srv/www/virtualenvs/demo.example.org/lib/python2.6/site-packages/django/contrib/staticfiles/management/commands/collectstatic.py", line 275, in link_file
    os.symlink(source_path, full_path)
OSError: [Errno 17] File exists

I switched moduled here, hence the symlinks of the previous "filebrowser" were still there, but no longer pointed to an existing file.
The same also happens when one reorganized the project layout, while.

How to reproduce:

• Have a project with 1 app.
• run ./manage.py collectstatic --link
• Rename that app, or move it to a sub package.
• run ./manage.py collectstatic --link again.

[wim@…]

Hehe I ran into the same issue not too long ago, when I too was dealing with a filebrowser.

[wim@…]

Hi John, does your patch not leave the broken link, in stead of replacing it by the new one?

[John Giannelos]

Hi, sorry for not showing a sign of progress after that long time.
Yes, the patch I had sent left the broken link instead of replacing it.
I am attaching an updated patch that removes the dangling symlink first.

[John Giannelos]

Updated patch with tests.

[Jannis Leidel <jannis@…>]

In f90be002d9d3c10b87c74741986e2cbf9f2b858e:

Fixed #20780 -- Get rid of stale symlinks when using collectstatic.

Thanks to John Giannelos for the initial patch.