GNU bug report logs - #23650
Use of locate-file for directories is underdocumented

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Nikolay Kudryavtsev <nikolay.kudryavtsev <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Use of locate-file for directories is underdocumented
Date: Mon, 30 May 2016 01:44:11 +0300

[Message part 1 (text/plain, inline)]

Hello.

Let's say I have a list of folders A, B, C. I want to find which one of 
them contains subfolder D.

My first idea was using locate-file. While doing so I've found that the 
Elisp reference for it is incomplete and confusing:

1. According to the docstring it would only return a directory if 
PREDICATE returns 'dir-ok. This is not mentioned in the Elisp reference.

2. The reference suggests file-directory-p as a useful predicate and 
this would fail due to 1.

3. It's probably a good idea to mention that there are no bundled 
predicates that return dir-ok, and suggest to use a lamda like this: 
(lambda (f) (and (file-directory-p f) 'dir-ok)) as a PREDICATE.


Here's a working example, just in case:

(locate-file "Git" '("c:/Program Files/") nil (lambda (f) (and 
(file-directory-p f) 'dir-ok)))

-- 
Best Regards,
Nikolay Kudryavtsev

[Message part 2 (text/html, inline)]

Message #8 received at 23650 <at> debbugs.gnu.org (full text, mbox):

From: Noam Postavsky <npostavs <at> users.sourceforge.net>
To: Nikolay Kudryavtsev <nikolay.kudryavtsev <at> gmail.com>
Cc: 23650 <at> debbugs.gnu.org
Subject: Re: bug#23650: Use of locate-file for directories is underdocumented
Date: Tue, 30 Jan 2018 22:40:59 -0500

tags 23650 fixed
close 23650 26.1
quit

Nikolay Kudryavtsev <nikolay.kudryavtsev <at> gmail.com> writes:

> 1. According to the docstring it would only return a directory if
> PREDICATE returns 'dir-ok. This is not mentioned in the Elisp
> reference.
>
> 2. The reference suggests file-directory-p as a useful predicate and
> this would fail due to 1.
>
> 3. It's probably a good idea to mention that there are no bundled
> predicates that return dir-ok, and suggest to use a lamda like this:
> (lambda (f) (and (file-directory-p f) 'dir-ok)) as a PREDICATE.
>
>
> Here's a working example, just in case:
>
> (locate-file "Git" '("c:/Program Files/") nil (lambda (f) (and
> (file-directory-p f) 'dir-ok)))

Added a clarifiction and a similar example (though not one with w32
path) in emacs-26.

[1: f706c59093]: 2018-01-30 22:14:02 -0500
  Update manual description of locate-file (Bug#23650)
  https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=f706c59093645a6306dd907833d597884e69c0ac

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