How to define xref-find-definitions for a new mode?

How to define xref-find-definitions for a new mode?

[Marcin Borkowski]

Hi all,

I'd like to define xref-find-definitions for LaTeX (in AUCTeX).  Where
should I start?  Is there any documentation on how to add a new mode
support to xref?

TIA,

-- 
Marcin Borkowski
http://mbork.pl

Re: How to define xref-find-definitions for a new mode?

[Eli Zaretskii]

> From: Marcin Borkowski <mbork@mbork.pl>
> Date: Sat, 09 Jun 2018 08:46:07 +0200
> 
> I'd like to define xref-find-definitions for LaTeX (in AUCTeX).  Where
> should I start?  Is there any documentation on how to add a new mode
> support to xref?

The only documentation is in xref.el itself.  In a nutshell, you need
to implement a couple of methods in a way that is specific to LaTeX.

(Btw, doesn't it already work?  Etags is an existing back-end for
Xref, and 'etags' the program already supports TeX and its
derivatives, so it is able to create TAGS tables for LaTeX files.)

Re: How to define xref-find-definitions for a new mode?

[Marcin Borkowski]

On 2018-06-09, at 10:47, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Marcin Borkowski <mbork@mbork.pl>
>> Date: Sat, 09 Jun 2018 08:46:07 +0200
>> 
>> I'd like to define xref-find-definitions for LaTeX (in AUCTeX).  Where
>> should I start?  Is there any documentation on how to add a new mode
>> support to xref?
>
> The only documentation is in xref.el itself.  In a nutshell, you need
> to implement a couple of methods in a way that is specific to LaTeX.

Thanks.  Are there other places I could look into, like xref
implementation for a concrete language?

> (Btw, doesn't it already work?  Etags is an existing back-end for
> Xref, and 'etags' the program already supports TeX and its
> derivatives, so it is able to create TAGS tables for LaTeX files.)

Well, possibly, but I'd like it to work like for Elisp or JavaScript,
without a TAGS table.  Also, I want it to go to \label when on \ref, to
\bib / \bibitem when on \cite etc.

Thanks,

-- 
Marcin Borkowski
http://mbork.pl

Re: How to define xref-find-definitions for a new mode?

[Eli Zaretskii]

> From: Marcin Borkowski <mbork@mbork.pl>
> Cc: help-gnu-emacs@gnu.org
> Date: Sat, 09 Jun 2018 11:10:22 +0200
> 
> Thanks.  Are there other places I could look into, like xref
> implementation for a concrete language?

In the sources for the respective languages, notably Lisp.  Search for
"xref-".

> > (Btw, doesn't it already work?  Etags is an existing back-end for
> > Xref, and 'etags' the program already supports TeX and its
> > derivatives, so it is able to create TAGS tables for LaTeX files.)
> 
> Well, possibly, but I'd like it to work like for Elisp or JavaScript,
> without a TAGS table.

Is this likely to happen?  Lisp and JavaScript know where to find
functions and variables because they keep that information as part of
defining them.  I don't think TeX does anything similar, does it?

> Also, I want it to go to \label when on \ref, to \bib / \bibitem
> when on \cite etc.

Are you sure it doesn't work already?  E.g., if \label is tagged, then
"M-." on the tag's name at \ref should go to the label's definition.

Re: How to define xref-find-definitions for a new mode?

[Marcin Borkowski]

On 2018-06-09, at 11:48, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Marcin Borkowski <mbork@mbork.pl>
>> Cc: help-gnu-emacs@gnu.org
>> Date: Sat, 09 Jun 2018 11:10:22 +0200
>>
>> Thanks.  Are there other places I could look into, like xref
>> implementation for a concrete language?
>
> In the sources for the respective languages, notably Lisp.  Search for
> "xref-".
>
>> > (Btw, doesn't it already work?  Etags is an existing back-end for
>> > Xref, and 'etags' the program already supports TeX and its
>> > derivatives, so it is able to create TAGS tables for LaTeX files.)
>>
>> Well, possibly, but I'd like it to work like for Elisp or JavaScript,
>> without a TAGS table.
>
> Is this likely to happen?  Lisp and JavaScript know where to find
> functions and variables because they keep that information as part of
> defining them.  I don't think TeX does anything similar, does it?

Why couldn't it (at least in theory)?  If etags can do it, why not
Emacs?  Also, I'm not sure JS does that.

>> Also, I want it to go to \label when on \ref, to \bib / \bibitem
>> when on \cite etc.
>
> Are you sure it doesn't work already?  E.g., if \label is tagged, then
> "M-." on the tag's name at \ref should go to the label's definition.

Well, apparently it doesn't without the TAGS file.  And even with it,
I couldn't make it to work.  Also, amsrefs is not suppported.

Best,

--
Marcin Borkowski
http://mbork.pl

Re: How to define xref-find-definitions for a new mode?

[Eli Zaretskii]

> From: Marcin Borkowski <mbork@mbork.pl>
> Cc: help-gnu-emacs@gnu.org
> Date: Mon, 11 Jun 2018 05:22:26 +0200
> 
> >> > (Btw, doesn't it already work?  Etags is an existing back-end for
> >> > Xref, and 'etags' the program already supports TeX and its
> >> > derivatives, so it is able to create TAGS tables for LaTeX files.)
> >>
> >> Well, possibly, but I'd like it to work like for Elisp or JavaScript,
> >> without a TAGS table.
> >
> > Is this likely to happen?  Lisp and JavaScript know where to find
> > functions and variables because they keep that information as part of
> > defining them.  I don't think TeX does anything similar, does it?
> 
> Why couldn't it (at least in theory)?  If etags can do it, why not
> Emacs?

You said "no TAGS", so do you mean you want to rewrite the TeX part of
etags in Lisp, and make that run in real-time, when the user types
"M-."?  Won't this be too slow.

> Also, I'm not sure JS does that.

Me neither, but it was you who mentioned JS, not me ;-)

> >> Also, I want it to go to \label when on \ref, to \bib / \bibitem
> >> when on \cite etc.
> >
> > Are you sure it doesn't work already?  E.g., if \label is tagged, then
> > "M-." on the tag's name at \ref should go to the label's definition.
> 
> Well, apparently it doesn't without the TAGS file.  And even with it,
> I couldn't make it to work.  Also, amsrefs is not suppported.

Then my suggestion would be to extend etags to support that.  That way
you won't be starting from scratch.

Re: How to define xref-find-definitions for a new mode?

[Marcin Borkowski]

On 2018-06-11, at 17:13, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Marcin Borkowski <mbork@mbork.pl>
>> Cc: help-gnu-emacs@gnu.org
>> Date: Mon, 11 Jun 2018 05:22:26 +0200
>>
>> >> > (Btw, doesn't it already work?  Etags is an existing back-end for
>> >> > Xref, and 'etags' the program already supports TeX and its
>> >> > derivatives, so it is able to create TAGS tables for LaTeX files.)
>> >>
>> >> Well, possibly, but I'd like it to work like for Elisp or JavaScript,
>> >> without a TAGS table.
>> >
>> > Is this likely to happen?  Lisp and JavaScript know where to find
>> > functions and variables because they keep that information as part of
>> > defining them.  I don't think TeX does anything similar, does it?
>>
>> Why couldn't it (at least in theory)?  If etags can do it, why not
>> Emacs?
>
> You said "no TAGS", so do you mean you want to rewrite the TeX part of
> etags in Lisp, and make that run in real-time, when the user types
> "M-."?  Won't this be too slow.

Well, it works with JS pretty well (I don't know how it's implemented,
though).

>> >> Also, I want it to go to \label when on \ref, to \bib / \bibitem
>> >> when on \cite etc.
>> >
>> > Are you sure it doesn't work already?  E.g., if \label is tagged, then
>> > "M-." on the tag's name at \ref should go to the label's definition.
>>
>> Well, apparently it doesn't without the TAGS file.  And even with it,
>> I couldn't make it to work.  Also, amsrefs is not suppported.
>
> Then my suggestion would be to extend etags to support that.  That way
> you won't be starting from scratch.

Well, in that case I'll pass for now.  Etags is written in C, which
I don't speak very well.  (Learning it better would be great, but
I don't have enough time for that now.)

Thanks,

--
Marcin Borkowski
http://mbork.pl

Re: How to define xref-find-definitions for a new mode?

[Eli Zaretskii]

> From: Marcin Borkowski <mbork@mbork.pl>
> Cc: help-gnu-emacs@gnu.org
> Date: Fri, 15 Jun 2018 06:49:43 +0200
> 
> >> > Are you sure it doesn't work already?  E.g., if \label is tagged, then
> >> > "M-." on the tag's name at \ref should go to the label's definition.
> >>
> >> Well, apparently it doesn't without the TAGS file.  And even with it,
> >> I couldn't make it to work.  Also, amsrefs is not suppported.
> >
> > Then my suggestion would be to extend etags to support that.  That way
> > you won't be starting from scratch.
> 
> Well, in that case I'll pass for now.  Etags is written in C, which
> I don't speak very well.  (Learning it better would be great, but
> I don't have enough time for that now.)

You could instead file bug reports with reproducible recipes and with
requests for what should 'etags' the program add to TAGS to support
your features.  Then someone else could implement these changes in
'etags'.  It's known to have happened, including fairly recently.

Re: How to define xref-find-definitions for a new mode?

[Marcin Borkowski]

On 2018-06-15, at 09:41, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Marcin Borkowski <mbork@mbork.pl>
>> Cc: help-gnu-emacs@gnu.org
>> Date: Fri, 15 Jun 2018 06:49:43 +0200
>> 
>> >> > Are you sure it doesn't work already?  E.g., if \label is tagged, then
>> >> > "M-." on the tag's name at \ref should go to the label's definition.
>> >>
>> >> Well, apparently it doesn't without the TAGS file.  And even with it,
>> >> I couldn't make it to work.  Also, amsrefs is not suppported.
>> >
>> > Then my suggestion would be to extend etags to support that.  That way
>> > you won't be starting from scratch.
>> 
>> Well, in that case I'll pass for now.  Etags is written in C, which
>> I don't speak very well.  (Learning it better would be great, but
>> I don't have enough time for that now.)
>
> You could instead file bug reports with reproducible recipes and with
> requests for what should 'etags' the program add to TAGS to support
> your features.  Then someone else could implement these changes in
> 'etags'.  It's known to have happened, including fairly recently.

Thanks, this gives some hope!

-- 
Marcin Borkowski
http://mbork.pl

Re: How to define xref-find-definitions for a new mode?

[Dmitry Gutov]

On 6/9/18 12:10 PM, Marcin Borkowski wrote:

> Thanks.  Are there other places I could look into, like xref
> implementation for a concrete language?

etags and elisp-mode implenentations are built-in. They're a bit 
non-trivial though, so I'd look into reusing etags first, like Eli suggests.