bug#45474: Icomplete exhibiting in recursive minibuffer when it shouldn’t

[Gregory Heytings <gregory@heytings.org>]

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>>> If the M-: is not in a recursive minibuffer, everything is OK since 
>>> icomplete-simple-completing-p returns nil.
>>
>> Indeed; patch attached.  Ideally this should be done inside 
>> icomplete-minibuffer-setup, but if we did this (by checking 
>> minibuffer-completing-symbol), it would prevent icomplete-mode from 
>> being active in the opposite situation: M-: followed by C-x C-f.
>>
>> @@ -1754,7 +1754,9 @@ read--expression
>>            (set-syntax-table emacs-lisp-mode-syntax-table)
>>            (add-hook 'completion-at-point-functions
>>                      #'elisp-completion-at-point nil t)
>> -          (run-hooks 'eval-expression-minibuffer-setup-hook))
>> +          (run-hooks 'eval-expression-minibuffer-setup-hook)
>> +          ;; if we enter a recursive minibuffer, disable icomplete (bug#45474)
>> +          (setq-local icomplete-mode nil))
>
> Is this really specific only to read--expression? I can reproduce the 
> same issue with any command that doesn't use completion, e.g. C-x C-f 
> C-x f.
>

Indeed, but the bug report was only about read-expression.  It's far more 
annoying to see completion candidates when you want to type a complete 
expression than when you just have to enter a short argument.

Anyway, given that you asked for it, here's a more general solution.  I 
did not check all places where read-from-minibuffer is used, but adapting 
them is straightforward.

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From 7fc38f2a66f5545c276836d62a7e3a8669c3eb10 Mon Sep 17 00:00:00 2001
From: Gregory Heytings <gregory@heytings.org>
Date: Thu, 15 Apr 2021 22:27:08 +0000
Subject: [PATCH] Make it possible to disable icomplete-mode in recursive
 minibuffers

* lisp/icomplete.el (minibuffer-disable-icomplete-mode): New internal
variable.
(icomplete-minibuffer-setup): Disable icomplete-mode when
minibuffer-disable-icomplete-mode is non-nil

* lisp/subr.el (read-number, read-char-from-minibuffer, y-or-n-p): Use it.

* lisp/simple.el (read--expression): Use it.
---
 lisp/icomplete.el |  5 +++++
 lisp/simple.el    |  3 +++
 lisp/subr.el      | 17 ++++++++++++-----
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/lisp/icomplete.el b/lisp/icomplete.el
index d5b6f76d7b..551b8bdc4a 100644
--- a/lisp/icomplete.el
+++ b/lisp/icomplete.el
@@ -442,10 +442,15 @@ icomplete-simple-completing-p
                (eq icomplete-with-completion-tables t)
                (member table icomplete-with-completion-tables))))))
 
+(defvar minibuffer-disable-icomplete-mode nil)
+
 ;;;_ > icomplete-minibuffer-setup ()
 (defun icomplete-minibuffer-setup ()
   "Run in minibuffer on activation to establish incremental completion.
 Usually run by inclusion in `minibuffer-setup-hook'."
+  (when minibuffer-disable-icomplete-mode
+    (setq-local icomplete-mode nil)
+    (setq minibuffer-disable-icomplete-mode nil))
   (when (and icomplete-mode (icomplete-simple-completing-p))
     (setq-local icomplete--initial-input (icomplete--field-string))
     (setq-local completion-show-inline-help nil)
diff --git a/lisp/simple.el b/lisp/simple.el
index 999755a642..9626b3605f 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1739,6 +1739,8 @@ eval-expression-print-format
 (defvar eval-expression-minibuffer-setup-hook nil
   "Hook run by `eval-expression' when entering the minibuffer.")
 
+(defvar minibuffer-disable-icomplete-mode)
+
 (defun read--expression (prompt &optional initial-contents)
   "Read an Emacs Lisp expression from the minibuffer.
 
@@ -1755,6 +1757,7 @@ read--expression
           (add-hook 'completion-at-point-functions
                     #'elisp-completion-at-point nil t)
           (run-hooks 'eval-expression-minibuffer-setup-hook))
+      (setq minibuffer-disable-icomplete-mode t)
       (read-from-minibuffer prompt initial-contents
                             read-expression-map t
                             'read-expression-history))))
diff --git a/lisp/subr.el b/lisp/subr.el
index c2be26a15f..bc25fe234f 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2794,6 +2794,8 @@ read-passwd
 (defvar read-number-history nil
   "The default history for the `read-number' function.")
 
+(defvar minibuffer-disable-icomplete-mode)
+
 (defun read-number (prompt &optional default hist)
   "Read a numeric value in the minibuffer, prompting with PROMPT.
 DEFAULT specifies a default value to return if the user just types RET.
@@ -2812,6 +2814,7 @@ read-number
 					prompt t t))))
     (while
 	(progn
+	  (setq minibuffer-disable-icomplete-mode t)
 	  (let ((str (read-from-minibuffer
 		      prompt nil nil nil (or hist 'read-number-history)
 		      (when default
@@ -3052,8 +3055,10 @@ read-char-from-minibuffer
          ;; Protect this-command when called from pre-command-hook (bug#45029)
          (this-command this-command)
          (result
-          (read-from-minibuffer prompt nil map nil
-                                (or history 'empty-history)))
+          (progn
+            (setq minibuffer-disable-icomplete-mode t)
+            (read-from-minibuffer prompt nil map nil
+                                  (or history 'empty-history))))
          (char
           (if (> (length result) 0)
               ;; We have a string (with one character), so return the first one.
@@ -3247,9 +3252,11 @@ y-or-n-p
                        map))
              ;; Protect this-command when called from pre-command-hook (bug#45029)
              (this-command this-command)
-             (str (read-from-minibuffer
-                   prompt nil keymap nil
-                   (or y-or-n-p-history-variable 'empty-history))))
+             (str (progn
+                    (setq minibuffer-disable-icomplete-mode t)
+                    (read-from-minibuffer
+                     prompt nil keymap nil
+                     (or y-or-n-p-history-variable 'empty-history)))))
         (setq answer (if (member str '("y" "Y")) 'act 'skip)))))
     (let ((ret (eq answer 'act)))
       (unless noninteractive
-- 
2.30.2