Here are 3 scenarios I tested with fido-mode starting from emacs -Q (all of
these work perfectly with icomplete):
1. Files with spaces.
Run emacs -Q and use `M-x fido-mode' to activate fido-mode.
Create a file with a space in the name. Use find-file to try to open it. As soon as you
have a space in the minibuffer, it says "[No matches]".
For example, I created a file called "one two", and no other file in my home directory starts with
"one". In find-file when I type "one" I see the expected result: "~/one[ two] [Matched]".
If I press TAB to complete I get "one two [No matches]" (from there I can press RET to
open the file, this bug report is about the "[No matches]" which is
clearly wrong).
If after entering "one" I press space, I get "one [No matches]", that it, I no longer
get offered the "one two" completion.
2. Directories with spaces.
In emacs -Q use `M-x fido-mode' to activate fido-mode.
Create a directory with a space in the name. I created a directory called "a b" and put a file called "c" inside. If I run
find-file and type "a " (that's a followed by space), I see "~/a [No matches]". Even typing "a b/" gives me "~/a
b/ [No matches]", and neither TAB nor C-M-i (icomplete-force-complete) will complete the file "~/a b/c".
3. Menu entries in an info buffer.
In emacs -Q use `M-x fido-mode' to activate fido-mode.
Use `C-h i' to open the main info directory, pick an entry with a space in it. I have a "Date input format"
entry from coreutils, for example. Use `m' (bound to Info-menu) and type "Date". fido-mode does offer me the
relevant completions, and in my case, "Date input format" is the only one where "Date" is followed
by a space. If I type the space nothing happens (space is bound to minibuffer-complete-word), no space is entered, the
candidates don't change. Pressing space again pops up the completions buffer.
If I use `C-q SPC` to insert a literal space, I get "Date (No matches)".
If I skip the space and keep typing "inpu", it matches "Date input format", but pressing TAB to
complete it to the full "Date input format" again says "(No matches)" ---pressing RET will however
open the correct manual.
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This was initially meant to be a bug report for
`icomplete-fido-backward-updir', whose source code I read (but didn't run). It
uses `backward-kill-sexp', which means it won't fully go up a directory if it
has spaces in it. I suggest replacing (backward-kill-sexp 1) with
(zap-up-to-char -1 ?/), as follows:
(defun icomplete-fido-backward-updir ()
"Delete char before or go up directory, like `ido-mode'."
(interactive)
(if (and (eq (char-before) ?/)
(eq (icomplete--category) 'file))
(zap-up-to-char -1 ?/)
(call-interactively 'backward-delete-char)))
Before submitting that report I decided to test fido-mode and discovered it has
more fundamental problems with spaces than that.:)