Wordbreak issue when completing before end of line

repro.py

#!/usr/bin/env python
# PYTHON_ARGCOMPLETE_OK

import argparse
import argcomplete

parser = argparse.ArgumentParser()
parser.add_argument('--pass', choices=('name_one', 'name_two'))
parser.add_argument('--fail', choices=('name:one', 'name:two'))
parser.add_argument('--other')
argcomplete.autocomplete(parser)

The following completion in the middle of the line results in faulty completion:

$ ./repro.py --fail name:<TAB> --other

It becomes this:

$ ./repro.py --fail name:name: --other

Instead I’d expect to need to double-tab for this output:

$ ./repro.py --fail name:<TAB><TAB> --other
one  two  

For comparison, it works fine at the end of the line:

$ ./repro.py --fail name:<TAB><TAB>
one  two  

If an underscore is used instead of a colon, it works in the middle of the line or at the end:

$ ./repro.py --pass name_<TAB><TAB>
name_one  name_two  
$ ./repro.py --pass name_<TAB><TAB> --other
name_one  name_two  

This appears to be due to the lexer clearing last_wordbreak_pos here: https://github.com/kislyuk/argcomplete/blob/5a20d6165fbb4d4d58559378919b05964870cc16/argcomplete/my_shlex.py#L296-L297

Commenting out those two lines resolved the issue.

[kislyuk]

great point @evanunderscore, let’s leave that behavior as is.

[kislyuk]

Thanks for confirming @evanunderscore. I’ve been thinking about this and while I think we should proceed with #352 in the short term, I also hope we can enable a future where arguments after the cursor can affect parser state. This can be useful with mutually exclusive arguments, etc.

I’ll merge #352 and then try to scope out a design for what would be necessary to enable that, in a separate PR/issue.