_pytest._argcomplete.FastFilesCompleter fails when no prefix specified

[evanunderscore]

The overall effect of this is that pytest <tab> ends up using bash's default completer which completes just the files (no flags). This can be fixed by modifying the offending line to check if the prefix is non-empty, but I'm not sure if the current behavior (when _ARC_DEBUG is unset) actually desired.

To fix this and retain the current behavior, you could also modify try_argcomplete to call argcomplete.autocomplete(parser, always_complete_options=False).

$ export _ARC_DEBUG=1
$ pytest <tab>
[Trimmed argcomplete debug output]
Traceback (most recent call last):
  File "/usr/bin/pytest", line 11, in <module>
    sys.exit(main())
  File "/usr/lib/python2.7/site-packages/_pytest/config.py", line 49, in main
    config = _prepareconfig(args, plugins)
  File "/usr/lib/python2.7/site-packages/_pytest/config.py", line 168, in _prepareconfig
    pluginmanager=pluginmanager, args=args)
  File "/usr/lib/python2.7/site-packages/_pytest/vendored_packages/pluggy.py", line 745, in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
  File "/usr/lib/python2.7/site-packages/_pytest/vendored_packages/pluggy.py", line 339, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/usr/lib/python2.7/site-packages/_pytest/vendored_packages/pluggy.py", line 334, in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
  File "/usr/lib/python2.7/site-packages/_pytest/vendored_packages/pluggy.py", line 613, in execute
    return _wrapped_call(hook_impl.function(*args), self.execute)
  File "/usr/lib/python2.7/site-packages/_pytest/vendored_packages/pluggy.py", line 250, in _wrapped_call
    wrap_controller.send(call_outcome)
  File "/usr/lib/python2.7/site-packages/_pytest/helpconfig.py", line 68, in pytest_cmdline_parse
    config = outcome.get_result()
  File "/usr/lib/python2.7/site-packages/_pytest/vendored_packages/pluggy.py", line 280, in get_result
    _reraise(*ex)  # noqa
  File "/usr/lib/python2.7/site-packages/_pytest/vendored_packages/pluggy.py", line 265, in __init__
    self.result = func()
  File "/usr/lib/python2.7/site-packages/_pytest/vendored_packages/pluggy.py", line 614, in execute
    res = hook_impl.function(*args)
  File "/usr/lib/python2.7/site-packages/_pytest/config.py", line 957, in pytest_cmdline_parse
    self.parse(args)
  File "/usr/lib/python2.7/site-packages/_pytest/config.py", line 1126, in parse
    args = self._parser.parse_setoption(args, self.option, namespace=self.option)
  File "/usr/lib/python2.7/site-packages/_pytest/config.py", line 562, in parse_setoption
    parsedoption = self.parse(args, namespace=namespace)
  File "/usr/lib/python2.7/site-packages/_pytest/config.py", line 542, in parse
    try_argcomplete(self.optparser)
  File "/usr/lib/python2.7/site-packages/_pytest/_argcomplete.py", line 101, in try_argcomplete
    argcomplete.autocomplete(parser)
  File "/usr/lib/python2.7/site-packages/argcomplete/__init__.py", line 218, in __call__
    completions = self._get_completions(comp_words, cword_prefix, cword_prequote, last_wordbreak_pos)
  File "/usr/lib/python2.7/site-packages/argcomplete/__init__.py", line 248, in _get_completions
    completions = self.collect_completions(active_parsers, parsed_args, cword_prefix, debug)
  File "/usr/lib/python2.7/site-packages/argcomplete/__init__.py", line 461, in collect_completions
    completions)
  File "/usr/lib/python2.7/site-packages/argcomplete/__init__.py", line 415, in _complete_active_option
    prefix=cword_prefix, action=active_action, parser=parser, parsed_args=parsed_args)
  File "/usr/lib/python2.7/site-packages/_pytest/_argcomplete.py", line 81, in __call__
    if prefix[-1] == os.path.sep:  # we are on unix, otherwise no bash
IndexError: string index out of range

I'm using pytest 3.2.1.

(Be aware that kislyuk/argcomplete#225 may impact your ability to test this if you have installed pytest from a wheel.)

[nicoddemus]

Thanks @evanunderscore, would you like to open a PR with a fix?

[evanunderscore]

Sure, although I need someone to decide whether to suggest flags when there is no prefix.

Current:

$ pytest <tab><tab>
bar  baz  foo

Fixed:

$ pytest <tab><tab>
--assert                         --disable-warnings               --help                           --noconftest                     --setuponly
bar                              --doctest-glob                   --ignore                         -o                               --setup-only
--basetemp                       --doctest-ignore-import-errors   --import-mode                    --override-ini                   --setupplan
baz                              --doctest-modules                --junitprefix                    -p                               --setup-plan
-c                               --doctest-report                 --junit-prefix                   --pastebin                       --setupshow
--cache-clear                    --durations                      --junitxml                       --pdb                            --setup-show
--cache-show                     --exitfirst                      --junit-xml                      --pdbcls                         --showlocals
--capture                        --failed-first                   -k                               --pyargs                         --strict
--collect-in-virtualenv          --ff                             --keepduplicates                 --pythonwarnings                 --tb
--collectonly                    --fixtures                       --keep-duplicates                -q                               --traceconfig
--collect-only                   --fixtures-per-test              -l                               --quiet                          --trace-config
--color                          foo                              --last-failed                    -r                               -v
--confcutdir                     --fulltrace                      --lf                             --resultlog                      --verbose
--continue-on-collection-errors  --full-trace                     -m                               --result-log                     --version
--debug                          --funcargs                       --markers                        --runxfail                       -W
--disable-pytest-warnings        -h                               --maxfail                        -s                               -x

Alternate fixed:

$ pytest <tab><tab>
bar  baz  foo

[pavelrad]

argcomplete suggests flags too when there is no prefix, and this looks right, as you can use flags as well as paths/positional args in any order. But in this case, it makes sense to sort positional args after (or before) flags. But curl, git, bash, ping, for example, don't suggest options until you put a dash in command and this seems to be a best practice in Linux command-line tools.

[RonnyPfannschmidt]

i believe for now we should simply try to keep current pytest behaviour