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

[Madhu]

*  Eli Zaretskii <eliz@gnu.org> <86ed3jl63j.fsf@gnu.org>
Wrote on Sun, 10 Nov 2024 12:45:52 +0200
>> I was evaluating it under edebug after calling edebug-defun on
>> read-file-name-default, and ivoking (ffap) on the url.
>>
>> It returns the argument with or without the second parameter to
>> expand-file-name, and I was hoping I could count on this behaviour to
>> separate the urls from the files.
>>
>> The behaviour of expand-file-name is apparenlty modified when it comes
>> to read-file-name-default, but I can't spot what's going on. ?????
>
> Perhaps because TRAMP was loaded?
It's because of the call to
 (ffap-read-file-or-url "foo" "https://example.com/";)

which roughly does the equivalent of

(let ((file-name-handler-alist
       (cl-adjoin (cons ffap-url-regexp #'ffap--url-file-handler)
                  file-name-handler-alist)))
  (expand-file-name "https://example.com"; "~"))

Maybe the idea will still work?