Show all completions based on substring search

[Rudolf Adamkovič]

Howdy smart folks!

I noticed that Emacs (v29, 5b9b393c61) does not always show all
completions, the way I would like.

Given

  1. emacs -Q
  2. C-h f
  3. warning TAB,

I get the following 3 completions:

  warning-numeric-level
  warning-suppress-p
  warnings-suppress

Instead, I would like to see all candidates that contain the substring
`warning', such as `display-warning'.

I noticed that if I move the point to the beginning of the word
`warning' and type `TAB' there, then I get all candidates that contain
the substring `warning', including `display-warning'.

How can make the completion system *always* do this on `TAB', without
moving the point?  (Or using word completion, or typing the Orderless
separator, or anything else like that.)

I tried to set the `completion-styles' to the various documented values,
but I never seem to get all candidates I expect.

Thank you in advance for any help!

Rudy
-- 
"Logic is a science of the necessary laws of thought, without which no
employment of the understanding and the reason takes place."
-- Immanuel Kant, 1785

Rudolf Adamkovič <salutis@me.com> [he/him]
Studenohorská 25
84103 Bratislava
Slovakia