[PATCH] Question about completion behavior

[Ergus <spacibba@aol.com>]

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Please give a look to the attached patch...

It adds two new values:

visible: to update when visible else do nothing (as Stefan suggested).

always: to always update or show completions (Like bash
show-all-if-ambiguous)

BTW: the lazy value is more like show-all-if-unmodified i think


On Wed, Mar 09, 2022 at 03:30:16PM +0100, Ergus wrote:
>On Wed, Mar 09, 2022 at 03:16:17PM +0200, Eli Zaretskii wrote:
>>>Date: Wed, 9 Mar 2022 12:46:54 +0100
>>>From: Ergus <spacibba@aol.com>
>>>Cc: Stefan Monnier <monnier@iro.umontreal.ca>, emacs-devel@gnu.org
>>>
>>>Look at the attached patch, it may need some small improve to solve the
>>>case 4. but so far it gives a consistent behavior with any value of
>>>completion-auto-help (and it is actually simpler than the current code)
>>>
>>>Alternatively we may add another custom, something like:
>>>
>>>completions-on-complete-action which may have 3 possible values:
>>
>>We don't need a new option, we can add a new value to the
>>completion-auto-help.
>>
>>But yes, I think this behavior you propose _must_ be optional, most
>>probably opt-in for starters.  Not everyone will want it.
>>
>>See also completion-cycle-threshold: this new behavior should not
>>tramp that option.
>
>I tend to agree Eli, but actually I started a thread because the default
>behavior is indeed inconsistent with completion-auto-help as the same
>Stefan mentioned.
>
>The current behavior mixes the completion-auto-help==t with
>completion-auto-help=='lazy when there is some completion and the
>completions are already visible (hiding them).
>
>If we do:
>
>compi<tab> it should be completed, but if the completions list is
>somehow visible, then after the tab it is not correct, so we currently
>hide it, when we must just update it right?
>
>The fix in any case is extremely simple and I think that with a new vale
>for completion-auto-help to 'always it will work, but may be even
>complicated to explain in the documentation...
>
>

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diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 36b8d80841..c6a803cbc4 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -898,7 +898,11 @@ completion-auto-help
 is requested but cannot be done.
 If the value is `lazy', the *Completions* buffer is only displayed after
 the second failed attempt to complete."
-  :type '(choice (const nil) (const t) (const lazy)))
+  :type '(choice (const :tag "Disabled" nil)
+                 (const :tag "Enabled legacy" t)
+                 (const :tag "After a second attempt" lazy)
+                 (const :tag "Visible update" visible)
+                 (const :tag "Always update" always)))
 
 (defvar completion-styles-alist
   '((emacs21
@@ -1343,16 +1347,19 @@ completion--do-completion
               (completion--cache-all-sorted-completions beg end comps)
               (minibuffer-force-complete beg end))
              (completed
-              ;; We could also decide to refresh the completions,
-              ;; if they're displayed (and assuming there are
-              ;; completions left).
-              (minibuffer-hide-completions)
-              (if exact
-                  ;; If completion did not put point at end of field,
-                  ;; it's a sign that completion is not finished.
-                  (completion--done completion
-                                    (if (< comp-pos (length completion))
-                                        'exact 'unknown))))
+              (cond
+               (exact
+                ;; If completion did not put point at end of field,
+                ;; it's a sign that completion is not finished.
+                (minibuffer-hide-completions)
+                (completion--done completion
+                                  (if (< comp-pos (length completion))
+                                      'exact 'unknown)))
+               ((pcase completion-auto-help
+                  ('visible (get-buffer-window "*Completions*" 0))
+                  ('always t))
+                (minibuffer-completion-help beg end))
+               (t (minibuffer-hide-completions))))
              ;; Show the completion table, if requested.
              ((not exact)
 	      (if (pcase completion-auto-help