Empty "{posargs:foo}" gets replaced by "."

[pytoxbot]

• Bitbucket: https://bitbucket.org/hpk42/tox/issue/240
• Originally reported by: @blueyed
• Originally created at: 2015-04-28T09:29:36.818

Given the following tox.ini:

#!ini
[tox]
skipsdist = true
[testenv]
commands = echo {posargs:foo}
whitelist_externals = echo

Just using tox outputs foo, but when trying to pass no positional arguments . (a single dot) get passed:

  % tox -- ""
  python runtests: PYTHONHASHSEED='456438988'
  python runtests: commands[0] | echo .
  .
  _____________________________________ summary ______________________________________
    python: commands succeeded
    congratulations :)

[pytoxbot]

Original comment by @hpk42

fix issue240: allow to specify empty argument list without it being
rewritten to ".". Thanks Daniel Hahler.

→ <<cset 790d8f87af00>>

[pytoxbot]

Original comment by @blueyed

This gets triggered by the args_are_paths setting, which defaults to true.

The following patch fixes it:

diff -r 6210dea5abf1 tox/_config.py
--- a/tox/_config.py    Tue Apr 28 09:10:54 2015 +0200
+++ b/tox/_config.py    Tue Apr 28 09:48:58 2015 +0200
@@ -373,9 +373,10 @@
             if vc.args_are_paths:
                 args = []
                 for arg in config.option.args:
-                    origpath = config.invocationcwd.join(arg, abs=True)
-                    if origpath.check():
-                        arg = vc.changedir.bestrelpath(origpath)
+                    if arg != '':
+                        origpath = config.invocationcwd.join(arg, abs=True)
+                        if origpath.check():
+                            arg = vc.changedir.bestrelpath(origpath)
                     args.append(arg)
             reader.addsubstitutions(args)
         setenv = {}