master 0f7e343: * lisp/international/mule-cmds.el: Fix bug#38642

[Stefan Monnier]

branch: master
commit 0f7e3430bba031a6c5f45e0afe2ddcac197603cf
Author: Stefan Monnier <address@hidden>
Commit: Stefan Monnier <address@hidden>

    * lisp/international/mule-cmds.el: Fix bug#38642
    
    (universal-coding-system-argument): Adjust the code to the way
    `universal-argument` works nowadays.  Handle `prefix-arg` a bit more
    like `command_loop` does.
    
    * test/lisp/international/mule-tests.el
    (mule-cmds--test-universal-coding-system-argument): New test.
---
 lisp/international/mule-cmds.el       | 39 ++++++++++++++++-------------------
 test/lisp/international/mule-tests.el |  8 +++++++
 2 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/lisp/international/mule-cmds.el b/lisp/international/mule-cmds.el
index e4f5bb2..0a8a4aa 100644
--- a/lisp/international/mule-cmds.el
+++ b/lisp/international/mule-cmds.el
@@ -295,10 +295,14 @@ wrong, use this command again to toggle back to the right 
mode."
                (format "Coding system for following command (default %s): " 
default)
              "Coding system for following command: ")
            default))))
+  ;; FIXME: This "read-key-sequence + call-interactively" loop is trying to
+  ;; reproduce the normal command loop, but this "can't" be done faithfully so
+  ;; it necessarily suffers from breakage in corner cases (e.g. it fails to run
+  ;; pre/post-command-hook, doesn't properly set this-command/last-command, it
+  ;; doesn't handle keyboard macros, ...).
   (let* ((keyseq (read-key-sequence
                  (format "Command to execute with %s:" coding-system)))
-        (cmd (key-binding keyseq))
-        prefix)
+        (cmd (key-binding keyseq)))
     ;; read-key-sequence ignores quit, so make an explicit check.
     (if (equal last-input-event (nth 3 (current-input-mode)))
        (keyboard-quit))
@@ -309,28 +313,21 @@ wrong, use this command again to toggle back to the right 
mode."
       (while (progn
               (setq keyseq (read-key-sequence nil t)
                     cmd (key-binding keyseq t))
-              (not (eq cmd 'universal-argument-other-key)))
-       (let ((current-prefix-arg prefix-arg)
-             ;; Have to bind `last-command-event' here so that
-             ;; `digit-argument', for instance, can compute the
-             ;; `prefix-arg'.
-             (last-command-event (aref keyseq 0)))
-         (call-interactively cmd)))
-
-      ;; This is the final call to `universal-argument-other-key', which
-      ;; sets the final `prefix-arg'.
-      (let ((current-prefix-arg prefix-arg))
-       (call-interactively cmd))
-
-      ;; Read the command to execute with the given `prefix-arg'.
-      (setq prefix prefix-arg
-           keyseq (read-key-sequence nil t)
-           cmd (key-binding keyseq)))
+              (memq cmd '(negative-argument digit-argument
+                          universal-argument-more)))
+       (setq current-prefix-arg prefix-arg prefix-arg nil)
+       ;; Have to bind `last-command-event' here so that
+       ;; `digit-argument', for instance, can compute the
+       ;; `prefix-arg'.
+       (setq last-command-event (aref keyseq 0))
+       (call-interactively cmd)))
 
     (let ((coding-system-for-read coding-system)
          (coding-system-for-write coding-system)
-         (coding-system-require-warning t)
-         (current-prefix-arg prefix))
+         (coding-system-require-warning t))
+      (setq current-prefix-arg prefix-arg prefix-arg nil)
+      ;; Have to bind `last-command-event' e.g. for `self-insert-command'.
+      (setq last-command-event (aref keyseq 0))
       (message "")
       (call-interactively cmd))))
 
diff --git a/test/lisp/international/mule-tests.el 
b/test/lisp/international/mule-tests.el
index 678cbc2..881d92a 100644
--- a/test/lisp/international/mule-tests.el
+++ b/test/lisp/international/mule-tests.el
@@ -40,6 +40,14 @@
   (should (equal (encode-coding-char ?a 'ebcdic-int) "\201"))
   (should (not (multibyte-string-p (encode-coding-char ?a 'utf-8)))))
 
+(ert-deftest mule-cmds--test-universal-coding-system-argument ()
+  (skip-unless (not noninteractive))
+  (should (equal "ccccccccccccccccab"
+                 (let ((enable-recursive-minibuffers t)
+                       (unread-command-events
+                        (append (kbd "C-x RET c u t f - 8 RET C-u C-u c a b 
RET") nil)))
+                   (read-string "prompt:")))))
+
 ;; Stop "Local Variables" above causing confusion when visiting this file.