Incorrect case-handling when using find-file (Emacs 31.0.50)

[lmq-10]

• Start Emacs with emacs -Q
• Evaluate the following:

(add-to-list 'load-path "/path/to/vertico/source")
(require 'vertico)
(setq read-file-name-completion-ignore-case t)
(vertico-mode)

• Try to find a file with an upcased name using find-file. The expected behaviour is that downcased letters should match the upcased letters in the file name. However, they actually change the candidate casing instead, so the user most likely ends up finding a non-existent file.

This happens with the development version of Emacs, commit 882c849034a. Info:

GNU Emacs 31.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.49, cairo version 1.18.4) of 2025-05-11

Video showcase:

Videocaptura.de.pantalla_20250512_105419.webm

[minad]

Iirc there has been an upstream regression. Did you check if the problem also exists without Vertico? Please also try Emacs 30 if the problem exists there too. If not, it is an upstream problem.

[lmq-10]

Indeed, now that I test it, this happens without vertico too. This seems to be upstream bug #78323. I should have checked before. Sorry!

[minad]

Thanks for checking. I updated the bug report template, since I do not accept bug reports for unstable Emacs. They are almost always regressions in Emacs itself.