bug#16334: 24.3.50; company-capf eats the first char in IELM filename completions

[Stefan Monnier]

>>>>> `completion-file-name-table' is more of an exception, I think.  But if
>>>>> it was only passed the segment of STRING after the last path
>>>>> separator, it could still look behind it in the buffer and see the
>>>>> full path.
>>>> But the completion may actually want to *change* the text before
>>>> the boundary.  E.g. completion of /u/s/d to /usr/share/doc.
> Maybe I didn't ask the right question. If the completion may want to change
> the text outside of its defined boundaries, doesn't that subvert the meaning
> of the "boundaries"?

There are 2 levels: the level of try-completion, all-completions, an
completion-boundaries.  At that level, the completion should not affect
the text outside of the boundaries.  This is the level at which
completion-tables operate.

Then there's the level of completion-try-completion and
completion-all-completions.  This uses the info from the previous level
to implement completion according to completion-styles.  It can change
things outside of the boundaries.  This is part of the UI, not of
the backends.

>>> In that case, "/usr/share/doc" is the completion candidate, not "doc",
>>> right?
>> Not sure what you mean by "completion candidate":
> Elements returned by the completion table?

Then "/u/s/d" returns no completion candidates.

> Already done:
> https://github.com/company-mode/company-mode/compare/b70540b5fcd062c4670dea7004453de326ff4f70...8ecec3594931ae8e2329fec4b793ad4ba392e4ef

It's not in elpa yet.

> On the other hand, the backend is free to try all completion styles it

The backends know nothing about completion styles.

> We currently deal with that by only using the backends that respond with the
> same prefix as the first one that returned non-nil. Guess we could add the
> boundaries to the comparison list, too...

Exactly.


        Stefan