bug#35564: 27.0.50; [PATCH] Tweak dired-do-shell-command warning about "wildcard" characters

[Kévin Le Gouguec]

Hello,

The function dired-do-shell-command checks the user's command for any
star or question mark not surrounded by whitespace or backquotes,
asking whether they are deliberate, since the character will then be
sent as-is to the shell, instead of being replaced with the marked
file(s).

A silly example:

- Open a Dired buffer
- M-! echo "Foobar." > foo RET
- g
- with point on foo:
    - ! sed 's/\./?/' RET

The way the question is phrased bothers me:

> Confirm--do you mean to use `?' as a wildcard?

The first time I met this prompt was when I included a quoted '?' in
my command as in the example above, so I definitely did *not* mean to
use '?' as a shell wildcard.

Even now, knowing what the question really means, it still trips my
brain that I must answer "yes" (as in, "yes, I know Dired will not
substitute the marked files") when I mean "no" (as in, "no, I don't
mean to use '?' as a wildcard, what is this even ab- oh wait no right
I meant yes! Yes! 🤦").

I can think of a few ways to solve this:

1. Rephrase the question to be more general, specifically without
   calling the characters "wildcards"; for example:

> Confirm--do you mean to send `?' to the shell without substitution?

2. Parse the command to find out whether the shell will actually use
   these characters as wildcards.
    - not sure how portable this would be across different shells
    - AFAICT the aim of this prompt is simply to warn the user that
      Dired will not expand these characters; whether the shell will
      process them as wildcards is irrelevant

3. Add an option to skip this question (more of a workaround than a
   solution).

Favoring option #1, I tried to find alternative questions, but none of
the ones I came up with sounded satisfying (most of them included some
form of double-negation, which is not the kind of puzzle I want to
solve when I'm about to run a hastily-put-together Bash oneliner).

I played around with the idea of actually *showing* the
"unsubstituted" characters to the user in order to be able to say
something like…

> Confirm--the highlighted characters will not be substituted.
> Proceed?

… and ended up with the attached patch, which I am not entirely
satisfied with (for one, it replaces `y-or-n-p' with `yes-or-no-p'
merely because the former seems to strip my prompt's text attributes
somehow[1]).

0001-Make-dired-do-shell-command-highlight-unsubstituted-.patch
Description: Text Data

WDYT?  Assuming that Dired calling unsubstituted characters
"wildcards" is indeed a problem,

- can someone come up with a better phrasing?
- is the highlighting, as implemented in this patch, helpful?
- does anybody know why `y-or-n-p' prompts lose their face property?


Thank you for your time.

Kévin


[1] Compare:

(let ((prompt "foobar "))
  (add-face-text-property 3 6 'warning nil prompt)
  (yes-or-no-p prompt))

With:

(let ((prompt "foobar "))
  (add-face-text-property 3 6 'warning nil prompt)
  (y-or-n-p prompt))


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