bug#50508: 27.2; find-function ignore find-function-source-path

bug#50508: 27.2; find-function ignore find-function-source-path

[Thierry Volpiatto]

Hello,

according its docstring, find-function should honor
find-function-source-path but it doesn't, here from emacs -Q:

    (let ((find-function-source-path '("/home/thierry/tmp/emacs/lisp/emacs-lisp/")))
      (find-function 'find-function))
Jump to the definition of find-function in /usr/local/share/.../find-func.el.gz

However find-library-name is using it:

    (let ((find-function-source-path '("/home/thierry/tmp/emacs/lisp/emacs-lisp/")))
      (find-library-name "find-func"))
;; => "/home/thierry/tmp/emacs/lisp/emacs-lisp/find-func.el"

So either it is a bug or I misunderstand something.

Thanks. 
 


In GNU Emacs 27.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30, cairo version 1.15.10)
 of 2021-03-25 built on IPadS340
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Linux Mint 19.3

Recent messages:
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[mu4e] Indexing completed; processed 0, updated 0, cleaned-up 0
Imenu indexing buffers...done
Mark set [2 times]
Saving file /home/thierry/.emacs.d/save-scratch.el...
Wrote /home/thierry/.emacs.d/save-scratch.el
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-- 
Thierry

bug#50508: 27.2; find-function ignore find-function-source-path

[Lars Ingebrigtsen]

Thierry Volpiatto <thievol@posteo.net> writes:

> according its docstring, find-function should honor
> find-function-source-path but it doesn't, here from emacs -Q:
>
>     (let ((find-function-source-path '("/home/thierry/tmp/emacs/lisp/emacs-lisp/")))
>       (find-function 'find-function))
> Jump to the definition of find-function in /usr/local/share/.../find-func.el.gz
>
> However find-library-name is using it:
>
>     (let ((find-function-source-path '("/home/thierry/tmp/emacs/lisp/emacs-lisp/")))
>       (find-library-name "find-func"))
> ;; => "/home/thierry/tmp/emacs/lisp/emacs-lisp/find-func.el"
>
> So either it is a bug or I misunderstand something.

I'm not a sure whether it's a bug or not, but the functions certainly
don't work the way they're documented.  There's a lot of functions
involved here, but it looks like this has been broken for many years
(since before Emacs 25.1, at least).

Currently the implementation basically just looks a load-history, so
this is wrong:

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

That is, it doesn't do any searching at all, as far as I can tell.

`find-library-name', on the other hand, does search.

There's several different issues here.

1) If the function is defined, say, with `M-: (defun foo ())'
then `find-function-library' will return nil (which is correct), which
means that `find-function-search-for-symbol' will give up immediately.
But it's hard to say what it should do otherwise -- look in all .el
files in the load path to find it?  This is what it's documented to do:

---
If the file where FUNCTION is defined is not known, then it is
searched for in `find-function-source-path' if non-nil, otherwise
in `load-path'."
---

This functionality was apparently lost in this change

commit 2cd6a032aa501a3964be9d222e65bb44ba9960f7
Author:     Richard M. Stallman <rms@gnu.org>
AuthorDate: Mon Jun 29 17:23:25 1998 +0000

or...  well, I'm not sure, but it stopped doing regexp searches through
all .el files at some point, and instead just uses the load history.

I think fixing this isn't...  useful.

2) If the function was defined in a .el file (as this bug report
describes), then Emacs knows the name of the library.  But it doesn't
then use `find-library-name' to locate the library, but just uses
load-history.  Fixing this is pretty easy -- just use
`find-library-name' and use that instead of the value from
`load-history'.

Anybody else have any insights here?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#50508: 27.2; find-function ignore find-function-source-path

[Thierry Volpiatto]

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Lars Ingebrigtsen <larsi@gnus.org> writes:

> 2) If the function was defined in a .el file (as this bug report
> describes), then Emacs knows the name of the library.  But it doesn't
> then use `find-library-name' to locate the library, but just uses
> load-history.  Fixing this is pretty easy -- just use
> `find-library-name' and use that instead of the value from
> `load-history'.

Yes, this is working fine, it is what I am using actually.
https://github.com/emacs-helm/helm/blob/master/helm-lib.el#L1230


-- 
Thierry

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bug#50508: 27.2; find-function ignore find-function-source-path

[Lars Ingebrigtsen]

Thierry Volpiatto <thievol@posteo.net> writes:

> Lars Ingebrigtsen <larsi@gnus.org> writes:
>
>> 2) If the function was defined in a .el file (as this bug report
>> describes), then Emacs knows the name of the library.  But it doesn't
>> then use `find-library-name' to locate the library, but just uses
>> load-history.  Fixing this is pretty easy -- just use
>> `find-library-name' and use that instead of the value from
>> `load-history'.
>
> Yes, this is working fine, it is what I am using actually.
> https://github.com/emacs-helm/helm/blob/master/helm-lib.el#L1230

I'm just wondering whether it makes sense to fix 2) if we're not fixing
1), and I don't think fixing 1) is a good idea (it'd make the function
massively slower).

Instead I'm wondering whether we should just fix the doc strings here to
not mention `find-function-source-path' in `find-function' (etc), so
that the doc string matches the implementation, and instead mention
`find-library-name' (in the doc string) for your use case.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#50508: 27.2; find-function ignore find-function-source-path

[Thierry Volpiatto]

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Lars Ingebrigtsen <larsi@gnus.org> writes:

> Thierry Volpiatto <thievol@posteo.net> writes:
>
>> Lars Ingebrigtsen <larsi@gnus.org> writes:
>>
>>> 2) If the function was defined in a .el file (as this bug report
>>> describes), then Emacs knows the name of the library.  But it doesn't
>>> then use `find-library-name' to locate the library, but just uses
>>> load-history.  Fixing this is pretty easy -- just use
>>> `find-library-name' and use that instead of the value from
>>> `load-history'.
>>
>> Yes, this is working fine, it is what I am using actually.
>> https://github.com/emacs-helm/helm/blob/master/helm-lib.el#L1230
>
> I'm just wondering whether it makes sense to fix 2) if we're not fixing
> 1), and I don't think fixing 1) is a good idea (it'd make the function
> massively slower).
>
> Instead I'm wondering whether we should just fix the doc strings here to
> not mention `find-function-source-path' in `find-function' (etc), so
> that the doc string matches the implementation, and instead mention
> `find-library-name' (in the doc string) for your use case.

Yes sure, that's ok for me, I was just surprized to not be able to
let-bound `find-function-source-path` and run find-function just after
with the expected effect described in docstring, once you know it, you
can just write a function using `find-library-name` like I did.

Thanks.

-- 
Thierry

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bug#50508: 27.2; find-function ignore find-function-source-path

[Lars Ingebrigtsen]

Thierry Volpiatto <thievol@posteo.net> writes:

> Yes sure, that's ok for me, I was just surprized to not be able to
> let-bound `find-function-source-path` and run find-function just after
> with the expected effect described in docstring, once you know it, you
> can just write a function using `find-library-name` like I did.

Yup.  So I've now updated the documentation here, and I've also renamed
the variable to find-library-source-path (but kept the old name as an
obsolete variable alias).

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#50508: 27.2; find-function ignore find-function-source-path

[Thierry Volpiatto]

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Lars Ingebrigtsen <larsi@gnus.org> writes:

> Thierry Volpiatto <thievol@posteo.net> writes:
>
>> Yes sure, that's ok for me, I was just surprized to not be able to
>> let-bound `find-function-source-path` and run find-function just after
>> with the expected effect described in docstring, once you know it, you
>> can just write a function using `find-library-name` like I did.
>
> Yup.  So I've now updated the documentation here, and I've also renamed
> the variable to find-library-source-path (but kept the old name as an
> obsolete variable alias).

Great, thanks.

-- 
Thierry

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