Complete to matching common substring

[plk]

I am using vertico without orderless and want to get back the usual behaviour where tab completion fills the minibuffer with the common matching substring of matches. So, for example I have in the minibuffer:

/some/path/to/a/fi

and vertico is prompting with:

file1
file2
file3

I want TAB to make the minibuffer complete to:

/some/path/to/a/file

as with default emacs completion behaviour. Currently, TAB does nothing but display the vertico matches. Can't work out how to do this with vertico. Any help appreciated.

[minad]

See https://github.com/minad/vertico?tab=readme-ov-file#completion-styles-and-tab-completion. You probably want to bind TAB to minibuffer-complete.

[plk]

For me emacs -Q doesn't have vertico loaded or in the path so the second line just fails. I'll see if I can make a more minimal setup to test. Glad to see you are a biblatex/biber user ...

[plk]

This minimal setup with emacs -Q works and I see that the desired behaviour is fine with this:

(add-to-list 'load-path "~/.config/emacs/.local/straight/repos/vertico/")
(add-to-list 'load-path "~/.config/emacs/.local/straight/repos/compat/")
(require 'vertico)
(package-initialize)
(vertico-mode 1)
(keymap-set vertico-map "TAB" #'minibuffer-complete)

Now I have to try to find out what is stopping this in my config.

[minad]

It could be that you have some other completion styles configured via completion-category-overrides or completion-category-defaults. These will take precedence over the completion-styles variable.

[plk]

No customisation of those two - completion-category-overrides is nil and setting completion-category-defaults to nil doesn't help. I did notice that in the emacs -Q setup, completion-styles is undefined though ...

[minad]

It seems something is off with your setup or installation. By default completion-styles has the value (basic partial-completion emacs22). This variable is preloaded as part of minibuffer.el and certainly not undefined.

[plk]

Found it. Consult mode was being used and so it had to be set like this:

(use-package! consult
  :config
  (consult-customize consult-completion-in-region
                     :completion-styles '(basic))
  )

[plk]

Spoke too soon. It seemed to work but then I restarted Emacs and it doesn't again. Grr. In fact this makes no difference and doesn't seem to be recognised. It falls back on base completion-styles and even when this is set to just (basic) continues to not work for me. It obviously fails somewhere in the guts of consult--with-preview but I can't tell where yet.

[plk]

Finally found the issue. Vertico uses consult-completion-in-region which was the issue. Setting:

  (setq completion-in-region-function 'completion--in-region)

Fixes it. It seems to go into a recursive minibuffer thing with the consult function and you need to press return as many times as you pressed TAB to complete to get the actual file selected to display.