Determine whether to add a subparser to completion by its presence in _get_subactions()

[jimporter]

This is just a small change to the logic for when to generate completion for a subparser. The new logic is the same that argparse uses for showing a subparser in the list of options (i.e. if you don't pass help to add_parser, that subparser is omitted from your program's overall help message).

This is particularly important for subparsers which pass add_help=False in order to provide their own help implementation. This is something I do in one of my projects. See here and here for an example.

Note: this is a breaking change, since now subparsers with no help kwarg will no longer have shell-completion generated for them. I think this is the correct behavior though, and fixing this is easy enough for users of shtab: just set help to something like None or '' (or even better, add an actual help message!).

[casperdcl]

what about using help=argparse.SUPPRESS instead?

[jimporter]

what about using help=argparse.SUPPRESS instead?

Unfortunately, that results in myprogram --help printing "==SUPPRESS==" for the subcommand's help string. It seems the only way to hide the subcommand from the help listing is to omit the help argument when calling add_parser: https://github.com/python/cpython/blob/ac87b07a10e0ba2834e8de9cf0ea29a40fd882b1/Lib/argparse.py#L1166-L1170

As a further enhancement here, I notice that shtab uses subparser.description for the shell-completion help string. Since we can use the value of _get_subactions() to get the value of help, maybe it would be better to use that instead of the description (which might be too long to show anything useful in the shell).

Another thing I just noticed that I didn't account for is subcommand aliases. I'll write a test for this and fix the patch as needed...

[casperdcl]

slight tweaks

[codecov-commenter]

Codecov Report

Merging #47 (b1bf591) into master (76c5ead) will increase coverage by 0.22%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #47      +/-   ##
==========================================
+ Coverage   88.57%   88.80%   +0.22%     
==========================================
  Files           3        3              
  Lines         245      250       +5     
==========================================
+ Hits          217      222       +5     
  Misses         28       28              

Impacted Files	Coverage Δ
shtab/__init__.py	92.19% <100.00%> (+0.19%)	⬆️

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[casperdcl]

/tag v1.4.0 1e1d6ef

[jimporter]

Thanks for the quick review/merge!

[casperdcl]

Thanks for the contribution!