RE: C-x C-f, Tab (in)completion and visiting the wrong, new files

[Drew Adams]

> > In that case, you want TAB to complete only against existing files,
> > no? Then why not bind `file-file-existing'? That's what it's for.
>
> I think I suggested this originally. However, this would prevent
> users from creating new buffers as intended,

C-x b has lax completion.

It does not, however, follow `auto-mode-alist'. But see the recent
discussion about adding something similar for buffer names
(`buffer-auto-mode-alist').

> or it would require us
> to come up with a new (and short) key combination.

Just rebind C-x C-f, if that's your preference.

> I also thought that the input errors with the incomplete matches may
> be part of a common pattern that does not just apply to file names.
> In other completion cases where there is an ambiguity (e.g., M-x tex
> RET), the input is not accepted, and if there is no ambiguity, the
> input is autocompleted (e.g., M-x text RET).

Those are cases of strict completion, where the completed input must match a
candidate. They are equivalent to passing a non-nil REQUIRE-MATCH arg to
`completing-read'. `find-file' provides lax completion, and
`find-file-existing' provides strict completion - both are available.