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

[Liu Hui <liuhui1610@gmail.com>]

Hi,

> 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

I cannot find a working commit after a9941269683, which adds the two
text properties.

> 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).

I agree that completion-table-with-quoting is responsible.
pcomplete-annotation and pcomplete-help text properties can be
successfully shown by the completion UI (corfu/company) by applying
the following patch:

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index a3dc1b0cfbf..b0c32b938a0 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -700,6 +700,7 @@ completion--twq-all
            ;;  (concat (substring ustring 0 boundary)
            ;;          completion))
            ;; t)
+                   (add-text-properties 0 1 (text-properties-at 0
completion) qcompletion)
                    qcompletion))
                completions)
        qboundary))))

It just re-adds text properties to completions produced by
`completion-table-with-quoting', but I'm not sure it is the proper
fix. What do you think?