bug#8897: `completion--insert-strings' clobbers user-added text properties

[Štěpán Němec]

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

>> #+begin_src elisp
>> (let ((req (assoc-default n minibuffer-completion-table)))
>>   (concat " "
>>           (propertize (plist-get req :title)
>>                       'fontified t
>>                       'button '(t)
>>                       'category 'default-button
>>                       'help-echo "RET or mouse-2 for details"
>>                       'pr-data req
>>                       'action (lambda (b) (magithub-pull-request-details
>>                                            (button-get b 'pr-data))))))
>> #+end_src
>
> I must be missing something: where is a `face' or `mouse-face' property
> added?  The above code should not be affected by your patch, AFAICT.
> And I don't understand your comment about "but the button functions seem
> to set up the button face automatically" since I don't see where you
> call a button function before insertion.

Sorry for my confusing description. What I meant is that there is
apparently some magic involved that makes a string manufactured with a
`propertize' form like the one above appear as if it had the button face
(underlined), even though it's not explicitely among its text properties
(maybe the `category' does it? I don't know).

In any case, without my patch the face is overridden to become the usual
annotation italic, so it _does_ suffer from the problem I describe.

>> With my patch I haven't noticed any problems you mention -- clicking
>> or RET on the completion itself selects it, clicking or RET on the
>> annotation displays further details, the button face is preserved.
>
> I guess click&RET work OK because they're locally overridden, but if you
> run M-x choose-completion while on the button or if you hit `left' or
> `right' to skip from one completion to the next, you might see some
> problem (although not with the code quoted above which should not
> suffer from any of the problems discussed in this thread, AFAICT).

Indeed. I don't use the cursor keys, but you're right in that they seem
to include the button-like annotations among their jump targets; as for
`choose-completion', that seems to be bound to RET in the *Completions*
buffer, but as I said and in line with your guess, pressing RET on an
annotation actually invokes the button action as desired, so this
problem doesn't seem to occur.

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