bug#64902: 30.0.50; REQUIRE-MATCH completing-read arg in describe-* commands

[Thierry Volpiatto <thievol@posteo.net>]

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Stefan Monnier <monnier@iro.umontreal.ca> writes:

>>>> The problem is that with Helm completion I have an extra unknown
>>>> symbol on top of list when I start typing (this is expected when
>>>> require-match is non-nil),
>>> Could you characterize this "unknown symbol" a bit more?  I'm having
>>> trouble guessing why/how/where `confirm` would have such an effect.
>> In Helm, if require-match is 'confirm, when you write in minibuffer something
>> that doesn't match one of the candidates this string is appended on top
>> of list and is prefixed (with display prop) with [?]. By contrast when
>> require-match is nil nothing is appended on top of list and pressing RET
>> doesn't exit minibuffer (helm-buffer is empty in such case).
>> IOW the behavior of require-match is the same than with vanilla Emacs.
>
> I see.  So IIUC every piece works "correctly", but since it's *very*
> rare to want to use this ?-prefixed option in the case of
> `describe-function`, it looks/feels like a bug.

No, it is just annoying.

> The core of the problem is that in the normal UI, `confirm` is very
> lightweight (you'll basically only notice it when you do try to enter
> the name of a function that's not defined) whereas in the Helm UI it's
> harder to hide it.

I think 'confirm doesn't help, having to press twice on RET doesn't
explain what's going wrong to the user, I would expect something like:

i foo-test Not already defined

with "i" like invalid, foo-test highlighted, and "Not already defined"
explaining briefly what the symbol is.
This would show up only when completions-detailed is non nil.
See attached screenshot of C-h f with completions-detailed non nil.

> And I guess for other cases (like `find-file`) the use of the ?-prefixed
> option is sufficiently common to deserve being more visible?

For files the prefix is [+], which mean create a new file or directory
when pressing RET (will create a dir when new filename ends with "/"),
when using icons, the prefix is an icon for dir or file instead of [+].

>
>
>         Stefan


-- 
Thierry

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