bug#66224: [PATCH] Add optional PREDICATE argument to read-directory-name

[Joseph Turner]

Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Tue, 26 Sep 2023 18:16:40 -0700
>> From:  Joseph Turner via "Bug reports for GNU Emacs,
>>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>>
>> This patch makes read-directory-name accept an optional PREDICATE arg
>> so it can be used like read-file-name.
>
> Any rationale?

Mainly code clarity. If you want to prompt for a certain type of
directory, then IMO the intent is more clear like this:

(read-directory-name "Prompt: " "~/" nil nil nil #'my/predicate)

than like this:

(read-file-name "Prompt: " "~/" nil nil nil
                (lambda (filename)
                  (and (funcall #'file-directory-p filename)
                       (funcall #'my/predicate filename))))

Also, I think that it would follow the principle of least suprise to
have read-file-name and read-directory-name accept the same args.

>> @@ -1719,7 +1719,9 @@ combining @var{directory} (or the current buffer's 
>> default directory
>>  if @var{directory} is @code{nil}) and @var{initial}.  If both
>>  @var{default} and @var{initial} are @code{nil}, this function uses
>>  @var{directory} as substitute default, or the current buffer's default
>> -directory if @var{directory} is @code{nil}.
>> +directory if @var{directory} is @code{nil}.  The union of sixth arg
>> +@code{predicate} and @code{file-directory-p} is passed as the
>
> This should be elaborated: what is meant by "the union of sixth arg
> and 'file-directory-p'"?
>
>> +@code{predicate} argument to ‘read-file-name’.
>                                 ^^^^^^^^^^^^^^^^
> That should be @code{read-file-name}
>
>> +** 'read-directory-name' now accepts an optional PREDICATE argument.
>> +The union of sixth arg PREDICATE and 'file-directory-p' is passed
>> +as the PREDICATE argument to 'read-file-name'.
>
> Likewise here, regarding the "union" part.
>
> Also, since you submit the patch for the manual, this NEWS entry
> should be marked with "+++".
>
>>  Fifth arg INITIAL specifies text to start with.
>>  DIR should be an absolute directory name.  It defaults to
>> -the value of `default-directory'."
>> +the value of `default-directory'.
>> +The union of sixth arg PREDICATE and `file-directory-p' is passed
>> +as the PREDICATE argument to `read-file-name'."
>
> The "union" part again.

Thanks for the review!! Please see attached patch.

Best,

Joseph

0001-Add-optional-PREDICATE-argument-to-read-directory-na.patch
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