Re: master 431f8ff1e38: * lisp/imenu.el: Support more values for imenu-flatten (bug#70846)

[Juri Linkov <juri@linkov.net>]

>> > Note that when minibuffer-allow-text-properties is non-nil, you can
>> > already get the same original text properties from completing-read if
>> > you "select" your candidate by cycling, since that doesn't go through
>> > choose-completion which strips text properties.  It feels a bit
>> > surprising to have this separate variable that affects one kind of
>> > selection ("choosing") and not other kinds ("cycling", "expanding").
>> > IMO, it'd be better, if possible, to just cease stripping text
>> > properties in choose-completion altogether.  Note that choose-completion
>> > calls completion--replace to do the actual insertion, and that function
>> > already respects minibuffer-allow-text-properties.
>>
>> I agree that a new variable is unnecessary, so it would be better just
>> to preserve text properties in choose-completion unconditionally.
>> Unless there are objections this looks like the right thing to do.
>
> Does that mean completion candidates will always appear with their
> original text properties?  If so, I don't think it's TRT in all cases.
> Whether it's TRT depends on the use case, so a variable definitely
> seems like the way to go.

Like Eshel noted, the text properties are already discarded from the completion
candidate by default since the default value of minibuffer-allow-text-properties
is nil.

> However, AFAIU Eshel didn't mean to say we should always preserve text
> properties, he said we already have a variable to indicate whether
> properties are to be preserved.  So the issue, AFAIU, is whether we
> need _another_ variable, or should use a single one in both cases.

Indeed, the existing variable minibuffer-allow-text-properties
can be used for both cases.  So when choose-completion will preserve
text properties, then completion--replace will decide whether to
discard them based on the value of minibuffer-allow-text-properties.

But there is another separate problem: Eshel asked to replace
let-bindings around completing-read with the minibuffer-local value
of minibuffer-allow-text-properties.  However, this is impossible to do
because read-from-minibuffer called from completing-read can't use
a minibuffer-local value of minibuffer-allow-text-properties.