Re: [PATCH v2 1/1] completion: load completion file for external subcommand

From: SZEDER Gábor <szeder.dev@gmail.com>
Date: Apr 25, 2018, 14:40 UTC
Message-ID: <CAM0VKj=MVY15SbRanfhXP3pPjNEuhZ=dbQmhXox6n5AOFyz2oQ@mail.gmail.com>
In-Reply-To: <CAM0VKjmJBzBFDAi1FQAgytb82-Q7JhO+aOfKi=YBZ3YtNxwPTQ@mail.gmail.com>

On Mon, Apr 23, 2018 at 5:12 PM, SZEDER Gábor <szeder.dev@gmail.com> wrote:

Show 15 quoted lines

> On Thu, Apr 19, 2018 at 9:07 PM, Florian Gamböck <mail@floga.de> wrote:
>> On 2018-04-18 21:51, SZEDER Gábor wrote:
>>> I believe the main bash-completion repository can be found at:
>>>
>>>  https://github.com/scop/bash-completion.git
>>>
>>> This repository still contains the branch 'dynamic-loading'; for the
>>> record it points to 3b029892f6f9db3b7210a7f66d636be3e5ec5fa2.
>>>
>>> Two commits on that branch are worth mentioning:
>>>
>>>   20c05b43 (Load completions in separate files dynamically, get rid of
>>>             have()., 2011-10-12)
>>>   5baebf81 (Add _xfunc for loading and calling functions on demand,
>>>             use it in apt-get, cvsps, rsync, and sshfs., 2011-10-13)

Show 6 quoted lines

>>>> I think the easiest method is to use a function that is defined by
>>>> bash-completion v2.0+, namely __load_completion.
>>>
>>> This is wrong, __load_completion() was introduced in cad3abfc
>>> (__load_completion: New function, use in _completion_loader and _xfunc,
>>> 2015-07-15), and the first release tag containg it is '2.2' from 2016-03-03.

Show 7 quoted lines

>>> Would it be possible to use _xfunc() instead to plug that hole?  It seems
>>> the be tricky, because that function not only sources but also _calls_ the
>>> completion function.
>>
>> But isn't this exactly what we want?
>
> No, that's definitely not what we want.

In my previous emails I overlooked the _completion_loader() helper function.

It seems that this function does almost exactly what we want. It was introduced along with dynamic completion loading back in 20c05b43, so it's available for us even in older LTS/Enterprise releases. Since cad3abfc it's a wrapper around __load_completion() and thus benefits from all the improvements, notably searching for completion scripts in a user-specified directory ($BASH_COMPLETION_USER_DIR) or in the user's home directory ($XDG_DATA_HOME or ~/.local/...) as well. It loads the matching completion script, but does not call the completion function unconditionally.

The "almost" refers to he case when _completion_loader() can't find a completion script with a matching name to load, and then registers the _minimal() completion function for the given command to do basic path completion as fallback. I don't think this matters in practice, because in this case the given command is a git command in its dashed form, e.g. 'git-diff-index', and those have been deprecated for a long time.

I think all you need to do is run a s/__load_completion/_completion_loader/ on your patch and update the commit message with relevant bits from the above discussion.