Re: force initialization of a datatype?

[Dmitry Gutov]

On 11/07/2015 08:30 PM, Stephen Leake wrote:

> > Why can't we reuse the contents of those variables?
>
> `help-fns-describe-function-functions' is intended to be called from
> 'describe-function'; it puts the results in a buffer.

Indeed, I (mistakenly) meant the other one.

> `elisp-xref-find-def-functions' puts the results in a list of xrefs. So
> the code is different.

After looking at it more, I mostly agree. It has a distinct value: 
determining additional "type-and-file" combinations corresponding to the 
symbol in question, or something along these lines. (1)

Which extend the behavior of elisp--xref-find-definitions, which 
currently iterates over variables, functions, faces and aliases.

> Not all entries on `elisp-xref-find-def-functions' have a corresponding
> entry in `find-function-regexp-alist'; they are not equivalent.

The other entries seem to have their equivalents inside the 
elisp--xref-find-definitions definition. That probably means something.

> A difference between the list of things xref can display and those that
> describe-function can display is a bug (that includes more than just
> those two lists).

What about M-x find-function not finding certain definitions that 
xref-find-definitions can? I don't exactly have a solid idea for 
improvement, but it seems like xref-mode-local-overload returns a set of 
xrefs pointing to locations that M-x find-function can't jump to.

It'll only jump to the "original" function definition, right?

> ...
> There were a lot of such bugs when xref was introduced.
>
> I've fixed some of them with `elisp-xref-find-def-functions', others
> with other code in elisp--xref-find-definitions. There are still
> a few remaining; see the FIXMEs in elisp-mode.el.

Thank you.

The only relevant FIXME I see now mentions advised functions.

> You seem to be suggesting that there should be a way to write one
> function for both lists; that's certainly not possible.

You're right.

> We might be able to switch to a dispatching "display-function", with
> one backend for help buffers and one for xrefs. But that does not change
> the essential point that different code needs to be written for both.

Yes, we need different code to "display" the entities: convert them to 
xrefs on one side, and convert them to help buffer contents on the other 
side.

The code that produces the list of the entities, however, could be unified.

I'm not sure that help-fns-describe-function-functions is a close 
counterpart to elisp--xref-find-definitions, however (2). 
describe-symbol-backends seems to be closer to that.

(1) For that reason, the current name of this variable doesn't seem 
fitting: the functions don't find "definitions", they find distinct 
entities bearing the given name. The actual finding of definitions is 
delegated to find-func and its hooks.

(2) help-fns-describe-function-functions's purpose seems to be more 
along the lines of adding extra blurbs to the description of the same 
entity.