Re: [Matlab-emacs-discuss] completion and goto-function in matlab-mode (Doom emacs)

[Karthik C. <kar...@gm...>]

Hi Eric,

> I did look at the elisp backend which it advertised as the prime
> example.  That one is quite large compared to your patch.  Do you
> think the below would expand out to be much larger?  I'm considering
> if xref support would move into it's own file or not.

The xref support for MATLAB in my patch is very short (relatively)
because

- I wrote it as a wrapper around `matlab-shell-which-fcn', which does
  the heavy lifing of finding the function in question. Matlab-shell
  already has support for jumping to definitions so I reused it. The
  downside is that matlab-shell needs to be running for xref support to
  work. This is not ideal, but the alternative is to write code to find
  function definitions from scratch.

- Only jump to definition is implemented. Two other xref functions:
  `xref-backend-apropos' and `xref-find-references', are not implemented
  at all. I want to look into adding these, but I'm not sure right now
  how to go about it.

> I also note that the elisp version doesn't use require for xref, and
> your patch depends on the feature existing when the code loads.  I
> think it does so via:
>
>     (declare-function xref-make "xref" (summary location))
>
> Will that work here too?

I think `declare-function' keeps the byte-compiler from complaining and
doesn't do much else. This should help here, though, and checking if
xref is loaded should be unnecessary.

In summary, a slightly modified version of this patch can be included as
preliminary xref support for matlab-mode. It can be its own file if it's
expected to be expanded in the future with `xref-find-references' and
other functionality, and prehaps written in a way as to not require
matlab-shell to be running.

Attached is a patch (as a separate file) with some minor modifications
from last time. For it to be integrated into matlab-mode, one other
piece of configuration is needed:

    (add-hook 'xref-backend-definitions #'matlab-shell-xref-activate)

This needs to be added in the matlab-mode major mode definition in
`define-derived-mode matlab-mode' in matlab.el.

Karthik