When specifying a customizable variable foo-paths as follows:
(defcustom foo-paths nil
"Paths for foo-related things."
:group 'foo
:options '(foo-1 foo-2)
:type '(alist :key-type symbol :value-type (file :must-match t)))
There doesn't seem to be any enforcement of the value type in the Customize interface. I can enter any text I want for the values, not just a file (let alone an existing file).
Am I missing something here? The manual says:
(file :must-match t)
The value must be a file name for an existing file. The widget provides completion.
What completion is the widget providing? I don't see any; all I see is a plain text box.
I'm using Emacs 25.1.1.
M-TAB(orESC TAB) to complete a partial file name that you type. I think you're right that the:must-matchdoesn't seem to do what one would expect - completion seems to be lax, not strict. And yet the code (forwidget-file-prompt-value) does use(read-file-name prompt2 dir nil must-match file), wheremust-matchis non-nil. Seems like a bug, but likely someone else here will speak better to this. – Drew Feb 10 '17 at 15:16