Re: Add completion to compilation-read-command

[Spyros Roum <spyros.roum@posteo.net>]

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Philip Kaludercic wrote:
>> To make sure I understand correctly, when using `completing-read` to
>> read user input, that is narrowing,
>> while the `C-x <up>` and *Completions* buffer is completion.
> No, `completing-read' just invokes an interface, that frontends can
> implement a UI for.  The default UI provides a completing/expanding
> interface, while Vertico, Helm, Ivy, etc. do selecting/narrowing.  When
> using `completing-read' you cannot really assume one or the other, so in
> effect one has to find a middle ground.  It is best you try your code in
> emacs -Q without any changes and see how it behaves.  Things like SPC
> doing something else than you would expect is just one pitfall, others
> I can recall are providing text that is difficult to input (I wrote a
> package a few years back called "insert-kaomoji" that used
> `completing-read' to prompt the user eastern-style emoticons; it is easy
> to use with a selecting framework, but more inconvenient if the user is
> first made to complete a string that is difficult to write, as most of
> the characters are not easy to type).

I tried the attached patch with `emacs -q` and now I understand how this 
would be very annoying without something like vertico installed haha. 
Nevertheless, it seems to work!

I'm attaching a patch based on the conversation so far to get feedback on.

I believe I should also write something to the NEWS file.

Also, I'm wondering if this counts as non-trivial enough that I would 
need to sign the FSF copyright.

Regarding testing, as far as I can tell, there are currently no tests 
for `compilation-read-command`.
Should I add anything? If yes, I'll probably need someone to point to 
existing tests for similar things that I can copy from.

Am I forgetting anything else?

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From e1068206662913978d541f924205a0615f8d2d95 Mon Sep 17 00:00:00 2001
From: Spyros Roum <spyros.roum@posteo.net>
Date: Wed, 25 Dec 2024 17:32:31 +0200
Subject: [PATCH] Add option for making compilation-read-command use
 completing-read

---
 lisp/progmodes/compile.el | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/lisp/progmodes/compile.el b/lisp/progmodes/compile.el
index 6784a12fd63..a318937e96d 100644
--- a/lisp/progmodes/compile.el
+++ b/lisp/progmodes/compile.el
@@ -1797,12 +1797,34 @@ compilation-mode-font-lock-keywords
    '((compilation--ensure-parse))
    compilation-mode-font-lock-keywords))
 
-(defun compilation-read-command (command)
+(defun compilation-prompt-read-shell-command (command)
   (read-shell-command "Compile command: " command
                       (if (equal (car compile-history) command)
                           '(compile-history . 1)
                         'compile-history)))
 
+(defun compilation-prompt-read-command-with-completion (command)
+  (completing-read "Compile command: " compile-history
+                   nil nil command
+                   (if (equal (car compile-history) command)
+                       '(compile-history . 1)
+                     'compile-history)))
+
+(defcustom compilation-read-command-function
+  'compilation-prompt-read-shell-command
+  "Function used by `compilation-read-command' to get user's input.
+Defaults to `compilation-prompt-read-shell-command',
+but `compilation-prompt-read-command-with-completion' can be used instead for
+a completing version based on past runs."
+  :version "31.0"
+  :type 'function
+  :options '(compilation-prompt-read-command-with-completion))
+
+(defun compilation-read-command (command)
+  "Prompt user for command to run.
+`compilation-read-command-function' controls the way input is read from the minibuffer."
+  (funcall compilation-read-command-function command))
+
 \f
 ;;;###autoload
 (defun compile (command &optional comint)
-- 
2.47.1