bug#61283: 29.0.60; pcomplete-completions-at-point loses text properties, breaking pcomplete-from-help annotations

[Gregory Heytings <gregory@heytings.org>]

>
> 1. Start emacs -Q
> 2. Evaluate the following two test commands in the scratch buffer:
>
> (defun good ()
>  (interactive)
>  (pp (all-completions "" (nth 2 (pcomplete-completions-at-point)))))
>
> (defun bad ()
>  (interactive)
>  (pp (all-completions "-" (nth 2 (pcomplete-completions-at-point)))))
>
> 3. Run shell or eshell
> 4. Enter `xargs --' in order to complete command line options via
> `pcomplete-from-help'.
> 5. M-x good -> Printed completion strings will have pcomplete-annotation
> and pcomplete-help text properties. These are used by the
> :annotation-function and the :company-docsig function.
> 6. M-x bad -> Returned completion strings are stripped of their text
> properties.
> 7. When triggering completion manually by pressing TAB, there are
> no annotations displayed in the *Completions* buffer.
>
> If I recall correctly, this functionality worked at some point and the 
> text properties were not removed, such that annotations worked. The 
> culprit, which destroys the properties, seems to be 
> `completion-table-with-quoting' in `pcomplete-completions-at-point', but 
> I wasn't able to figure out which commit caused this (I did not do any 
> bisecting).
>

Sorry, I missed your earlier post.  There is no need to bisect in this 
case: 'pcomplete-from-help' was added in a994126968 (which means that it's 
new in Emacs 29), and the recipe above already gave the exact same result 
at that point.  I took a sample of four revisions between 
emacs-29/c18f9f155f and a994126968 (f102145d38, 07127e9c29, 4f114c0d95, 
809afde01d), and the result is always the same.