find-function-source-directory

find-function-source-directory

[Richard Copley]

I want 'find-function' to go to the .el files in my build directory
"c:/projects/emacs/", not the installed .el.gz files
in "c:/msys64/mingw64/share/emacs/27.0.50/". The docstring for
'find-function' suggests it's possible (but doesn't give an example):

    The library where FUNCTION is defined is searched for in
    ‘find-function-source-path’, if non-nil, otherwise in ‘load-path’.

I tried each of these in my init file, with no effect:

(setq find-function-source-path "c:/projects/emacs/")
(setq find-function-source-path "c:/projects/emacs/lisp/")
(setq find-function-source-path
      (mapcar
       (lambda (x)
         (if (string-match "\\`c:/msys64/mingw64/share/emacs/27.0.50/" x)
             (replace-match "c:/projects/emacs/" nil nil x)
           x))
       load-path))

Did I miss something?

Re: find-function-source-directory

[Eli Zaretskii]

> From: Richard Copley <rcopley@gmail.com>
> Date: Sun, 18 Feb 2018 16:16:03 +0000
> 
> I want 'find-function' to go to the .el files in my build directory
> "c:/projects/emacs/", not the installed .el.gz files
> in "c:/msys64/mingw64/share/emacs/27.0.50/". The docstring for
> 'find-function' suggests it's possible (but doesn't give an example):
> 
>     The library where FUNCTION is defined is searched for in
>     ‘find-function-source-path’, if non-nil, otherwise in ‘load-path’.
> 
> I tried each of these in my init file, with no effect:
> 
> (setq find-function-source-path "c:/projects/emacs/")
> (setq find-function-source-path "c:/projects/emacs/lisp/")
> (setq find-function-source-path
>       (mapcar
>        (lambda (x)
>          (if (string-match "\\`c:/msys64/mingw64/share/emacs/27.0.50/" x)
>              (replace-match "c:/projects/emacs/" nil nil x)
>            x))
>        load-path))
> 
> Did I miss something?

Anything that is called "path" should be a list of directories, nopt a
single file name (this is GNU, remember?).  So try something like
this:

  (setq find-function-source-path
    '("c:/projects/emacs/lisp/"
      "c:/projects/emacs/lisp/emacs-lisp/"
      "c:/projects/emacs/lisp/net/"
      ...))

(add more subdirectories instead of the ellipsis).

Re: find-function-source-directory

[Eli Zaretskii]

> Date: Sun, 18 Feb 2018 20:40:50 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> 
>   (setq find-function-source-path
>     '("c:/projects/emacs/lisp/"
>       "c:/projects/emacs/lisp/emacs-lisp/"
>       "c:/projects/emacs/lisp/net/"
>       ...))
> 
> (add more subdirectories instead of the ellipsis).

This notwithstanding, I think that doc string is misleading: what you
want to accomplish isn't possible, because find-function-source-path
cannot override load-path in this use case.  Or maybe I'm missing
something.

Re: find-function-source-directory

[Richard Copley]

On 18 February 2018 at 19:35, Eli Zaretskii <eliz@gnu.org> wrote:
>> Date: Sun, 18 Feb 2018 20:40:50 +0200
>> From: Eli Zaretskii <eliz@gnu.org>
>>
>>   (setq find-function-source-path
>>     '("c:/projects/emacs/lisp/"
>>       "c:/projects/emacs/lisp/emacs-lisp/"
>>       "c:/projects/emacs/lisp/net/"
>>       ...))
>>
>> (add more subdirectories instead of the ellipsis).
>
> This notwithstanding, I think that doc string is misleading: what you
> want to accomplish isn't possible, because find-function-source-path
> cannot override load-path in this use case.  Or maybe I'm missing
> something.

Ah, thanks. (Sorry, I missed this message earlier.)
I'm wondering if there is there any use for
find-function-source-path, if not that. Perhaps it
is an ex-feature?

Re: find-function-source-directory

[tomas]

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On Mon, Feb 19, 2018 at 11:13:12AM +0000, Richard Copley wrote:
> On 18 February 2018 at 19:35, Eli Zaretskii <eliz@gnu.org> wrote:
> >> Date: Sun, 18 Feb 2018 20:40:50 +0200
> >> From: Eli Zaretskii <eliz@gnu.org>
> >>
> >>   (setq find-function-source-path
> >>     '("c:/projects/emacs/lisp/"
> >>       "c:/projects/emacs/lisp/emacs-lisp/"
> >>       "c:/projects/emacs/lisp/net/"
> >>       ...))
> >>
> >> (add more subdirectories instead of the ellipsis).
> >
> > This notwithstanding, I think that doc string is misleading: what you
> > want to accomplish isn't possible, because find-function-source-path
> > cannot override load-path in this use case.  Or maybe I'm missing
> > something.
> 
> Ah, thanks. (Sorry, I missed this message earlier.)
> I'm wondering if there is there any use for
> find-function-source-path, if not that. Perhaps it
> is an ex-feature?


Hm. Looking at the elisp sources, it seems to me that this variable
is used (cf. find-library-name) in a way that corresponds with its
docstring. An extract:

  (defun find-library-name (library)
    "Return the absolute file name of the Emacs Lisp source of LIBRARY.
  LIBRARY should be a string (the name of the library)."
    ;; If the library is byte-compiled, try to find a source library by
    ;; the same name.
    (when (string-match "\\.el\\(c\\(\\..*\\)?\\)\\'" library)
      (setq library (replace-match "" t t library)))
    (or
     (locate-file library
                  (or find-function-source-path load-path)
                  (find-library-suffixes))
    [...]

So definitely not an ex-feature (at least not on 27.0.50).

I don't know why ti isn't doing what you expect, though...

Cheers
- -- t
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Re: find-function-source-directory

[Eli Zaretskii]

> Date: Mon, 19 Feb 2018 12:44:20 +0100
> From: <tomas@tuxteam.de>
> 
> > > This notwithstanding, I think that doc string is misleading: what you
> > > want to accomplish isn't possible, because find-function-source-path
> > > cannot override load-path in this use case.  Or maybe I'm missing
> > > something.
> > 
> > Ah, thanks. (Sorry, I missed this message earlier.)
> > I'm wondering if there is there any use for
> > find-function-source-path, if not that. Perhaps it
> > is an ex-feature?
> 
> 
> Hm. Looking at the elisp sources, it seems to me that this variable
> is used (cf. find-library-name) in a way that corresponds with its
> docstring. An extract:

Yes, I've seen that as well.  But it turns out the code pulls a few
rabbits out of its hat before it even gets there: it uses load-history
and other related stuff, which gives absolute file names, so no need
to search any directories.

I propose to step in Edebug through the function and its subroutines,
and see what happens.  It looks like it uses different approaches for
preloaded symbols, autoloaded symbols, and the rest.  I didn't have
enough time to figure out all the details, but one thing that tripped
me was that, even if I start with a symbol that is neither preloaded
nor autoloaded, fairly soon it becomes boundp or fboundp, which means
Emacs loads its package, and at that time, there's no reason for Emacs
to do any path search.

If someone actually figures out what the code does, please tell the
details, as I'm quite sure we will have to update the doc string.

Thanks.

Re: find-function-source-directory

[tomas]

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On Mon, Feb 19, 2018 at 05:36:31PM +0200, Eli Zaretskii wrote:
> > Date: Mon, 19 Feb 2018 12:44:20 +0100
> > From: <tomas@tuxteam.de>

> > Hm. Looking at the elisp sources, it seems to me that this variable
> > is used [...]

> Yes, I've seen that as well.  But it turns out the code pulls a few
> rabbits out of its hat before it even gets there [...]

Uh, oh. Rabbits in Emacs ;-/

I'll try to have a look this afternoon. No guarantees, though :-)

Cheers&thanks
- -- tomás
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RE: find-function-source-directory

[Drew Adams]

> Anything that is called "path" should be a list of directories, nopt a
> single file name (this is GNU, remember?).  So try something like
> this:
> 
>   (setq find-function-source-path
>     '("c:/projects/emacs/lisp/"
>       "c:/projects/emacs/lisp/emacs-lisp/"
>       "c:/projects/emacs/lisp/net/"
>       ...))

FWIW, I don't think Emacs calls even such a list a "path".

I'd suggest a name such as `find-function-source-dirs'
or `find-function-source-directories' or
`find-function-source-dir-list'.

The value is a list of directories.  If you want the
name to also reflect the usage, then add a words such
as "lookup" (or whatever is most appropriate for the use).

Re: find-function-source-directory

[Eli Zaretskii]

> Date: Sun, 18 Feb 2018 11:53:19 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> 
> > Anything that is called "path" should be a list of directories, nopt a
> > single file name (this is GNU, remember?).  So try something like
> > this:
> > 
> >   (setq find-function-source-path
> >     '("c:/projects/emacs/lisp/"
> >       "c:/projects/emacs/lisp/emacs-lisp/"
> >       "c:/projects/emacs/lisp/net/"
> >       ...))
> 
> FWIW, I don't think Emacs calls even such a list a "path".
> 
> I'd suggest a name such as `find-function-source-dirs'
> or `find-function-source-directories' or
> `find-function-source-dir-list'.
> 
> The value is a list of directories.

In GNU, a "path" is a list of directories.  The separator is
colon/semi-colon in a shell, but in Lisp it's a simple list.  Cf.
load-path, exec-path, image-load-path, etc.

RE: find-function-source-directory

[Drew Adams]

> In GNU, a "path" is a list of directories.  The separator is
> colon/semi-colon in a shell, but in Lisp it's a simple list.  Cf.
> load-path, exec-path, image-load-path, etc.

Oops; yes, that's true.  It's generally a list of
directories that are searched, or otherwise processed,
in order.

Re: find-function-source-directory

[Richard Copley]

On 18 February 2018 at 21:56, Drew Adams <drew.adams@oracle.com> wrote:
>> In GNU, a "path" is a list of directories.  The separator is
>> colon/semi-colon in a shell, but in Lisp it's a simple list.  Cf.
>> load-path, exec-path, image-load-path, etc.
>
> Oops; yes, that's true.  It's generally a list of
> directories that are searched, or otherwise processed,
> in order.

I know, thanks. I have already tried that and it didn't
work -- see the last lisp expression in my OP.