GNU bug report logs - #74208
31.0.50; minibuffer read-file-name-default mutates global value of default-directory incorrectly

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Madhu <enometh <at> meer.net>
Subject: bug#74208: closed (Re: bug#74208: 31.0.50; minibuffer
 read-file-name-default mutates global value of default-directory
 incorrectly)
Date: Mon, 09 Dec 2024 08:18:02 +0000

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Your bug report

#74208: 31.0.50; minibuffer read-file-name-default mutates global value of default-directory incorrectly

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 74208 <at> debbugs.gnu.org.

-- 
74208: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=74208
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Michael Albinus <michael.albinus <at> gmx.de>
To: Madhu <enometh <at> meer.net>
Cc: 74208-done <at> debbugs.gnu.org
Subject: Re: bug#74208: 31.0.50; minibuffer read-file-name-default mutates
 global value of default-directory incorrectly
Date: Mon, 09 Dec 2024 09:17:20 +0100

Version: 31.1

Madhu <enometh <at> meer.net> writes:

Hi Madhu,

> I meant the defaulting use in the call to get_current_directory in
> callproc.c

I see. But as said, it isn't a robust setting:

--8<---------------cut here---------------start------------->8---
# env HOME=/foo emacs -Q --batch --eval '(let ((default-directory (expand-file-name "~"))) (shell-command "ls"))'

Error: file-missing ("Setting current directory" "No such file or directory" "/foo")
  call-shell-region(1 1 "ls" nil #<buffer *Shell Command Output*>)
  shell-command-on-region(1 1 "ls" nil nil nil)
  shell-command("ls")
  (let ((default-directory (expand-file-name "~"))) (shell-command "ls"))
  eval((let ((default-directory (expand-file-name "~"))) (shell-command "ls")) t)
  command-line-1(("--eval" "(let ((default-directory (expand-file-name \"~\"))) (shell-command \"ls\"))"))
  command-line()
  normal-top-level()

(Shell command failed with error)
Setting current directory: No such file or directory, /foo
--8<---------------cut here---------------end--------------->8---

> Speaking for myself: no. I'm a bit dissapointed that the setq doesn't
> get fixed, but I think the main problem has been addressed.

Thanks, so I'm closing the bug.

Best regards, Michael.

[Message part 3 (message/rfc822, inline)]

From: Madhu <enometh <at> meer.net>
To: bug-gnu-emacs <at> gnu.org
Subject: 31.0.50; minibuffer read-file-name-default mutates global value of
 default-directory incorrectly
Date: Tue, 05 Nov 2024 07:39:24 +0530 (IST)

minibuffer.el: (read-file-name-default) has the following code:
```
                     (minibuffer-with-setup-hook
                         (lambda ()
                           (setq default-directory dir)
		   ...
			  (set-syntax-table minibuffer-local-filename-syntax))
```

This mutates the global binding of default-directory which is incorrect.

To demonstrate the problem, in emacs -Q

(insert "http://example.com")
(setq enable-recursive-minibuffers t)

position point at in the middle of the string  http://example.com
M-: (ffap)

;; while waiting for input
M-: default-directory
;; => default-directory is bound to "http://example.com"
M-: (shell-command "echo foo")
; ;=>
;; Debugger entered--Lisp error: (file-missing "Setting current directory" "No such file or directory" "http://example.com/")

I think this can be addressed by binding default-directory before
modifying it.

```
diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -3671,6 +3671,7 @@ read-file-name-default
                               (expand-file-name dir))))
                     (minibuffer-with-setup-hook
                         (lambda ()
+                         (let ((default-directory default-directory))
                           (setq default-directory dir)
                           ;; When the first default in `minibuffer-default'
                           ;; duplicates initial input `insdef',
@@ -3689,7 +3690,7 @@ read-file-name-default
                                  (with-current-buffer
                                      (window-buffer (minibuffer-selected-window))
 				   (read-file-name--defaults dir initial))))
-			  (set-syntax-table minibuffer-local-filename-syntax))
+			  (set-syntax-table minibuffer-local-filename-syntax)))
                       (completing-read prompt 'read-file-name-internal
                                        pred require-match insdef
                                        'file-name-history default-filename)))
```

[I'm sending this before I forget so it can be reviewed, but I can
send this patch as as attachment if needed, and it'll take some more
time until I figure out how to write a test for it and test it.]

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