bug#48356: 28.0.50; choose-completion discards the suffix after the completion boundary

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

>>> ...which translates to "/" because of the double slash -- the filesystem
>>>   root directory (*). But that's the same data which would be used by any
>>>   other proposed solution, too.
>> More or less, tho the "ideal" solution is to do that in the
>> completion-style code, which has a bit more knowledge about it.
> Doing it in completion-style, though, would either require a relatively
> awkward change in most/all styles (e.g. the "new dynamic variable" route),
> or a more straightforward change in styles together with an incompatible
> change in completion-all-completions.

Yup, hence the quotes around "ideal".

> So on balance, would you say it's a good idea to a) use this approach in
> minibuffer-completion-help, b) create a named function for it, for other
> callers to take advantage of it as well?

Yes, while waiting for a new API it seems like a good stop gap.

> Looks like completion--merge-suffix is the helper to use.

Yup.

>> In theory this approach can "do the wrong thing" with some completion
>> styles, but AFAIK they haven't been written yet.  🙂
> So you figure that such theoretical style would return adjusted base-suffix
> in -all-completions method, not just in -try-completion?

A completion style could make use of (and list) things after the
boundary.  E.g. completing a file name like

    foo/ba<|>ar/baz

could decide to list all the files that match

    *f*o*o*/*b*a*a*r*/*b*a*z*

in which case the "end boundary" of the `completion-all-completions`
output should not be the `cdr` of the `completion-boundaries`.

I wouldn't worry about it, tho.


        Stefan