Re: Adding support for xref jumping to headers/interfaces

[Dmitry Gutov <dmitry@gutov.dev>]

On 11/11/2023 13:44, João Távora wrote:
> On Sat, Nov 11, 2023 at 12:58 AM Dmitry Gutov <dmitry@gutov.dev> wrote:
>>
>> On 09/11/2023 22:44, João Távora wrote:
>>> So I thought, that about 6 months ago we had established that
>>> "definition" and "reference" are two relatively safe concept to
>>> keep in xref.el, but other concepts should not be in there,
>>> because this doesn't scale well and could imposes awkward
>>> structure and hacks into an unknown number of backends.
>>>
>>> Has everyone changed their mind?
>>
>> My impression is that the first feedback from our patches actually made
>> people excited about things that _weren't_ included in the
>> previously-discussed plan, so it seems like a good idea to re-evaluate
>> it. Though not necessarily redo it all.
>>
>> Though I guess this particular mailing list might be biased in favor of
>> particular type of users (keyboard-driven, faster interaction as a
>> priority).
> 
> yeah, the sample size is so small that's it's more than certainly
> biased.

Most likely. It's too bad our actual audience here is quite small, and 
we don't have other reliable ways to collect feedback to prototypes.

Dropping an implementation into master is one way to test out a 
hypothesis, but it has inherent problems: the feedback comes late 
anyway, and quite often we'd end up having to maintain half-bakes 
features or unfortunate capabilities this way simply because they had 
been added and time had passed.

>>> What exactly bothers you
>>> about eglot-find-declaration/implementation/typeDefinition?
>>> In LSP-land these concepts_do_  make sense, because the
>>> LSP standard prescribes what servers should do with them.
>>
>> I think we've actually discovered that these kind of make sense for
>> Elisp too. They might not match the current implementation, but
>> conceptually, in some future, they might.
> 
> Yeah, they "kind of" make sense, but not very well and IMHO that's
> not a detail, but a big red flag.  It's clear, and I understand
> your point, that if we were to squint to contort to them we could
> have xref provide a consistent "works everywhere" UI.  But as
> Spencer noted it would be "works _mostly_ everywhere".  And, as I
> noted, the contortion might lead us up awkward alley, such as
> finding a list mixing `declare-function` and `declare (compiler-macro`
> in the bag of xref-find-declarations.

Why contort? From where I'm standing, 
declarations/implementations/typeDefinitions apply to almost any 
object-oriented language (C++/Java/Ruby/Python/JS), and even some 
functional ones.

Declarations might be less of a thing in some of those (mostly dynamic 
ones), but overall the list even makes a certain sense for Elisp (and 
similarly CL, I guess), at least in the OOP parts of them. And where 
they don't, one or two of these commands will fail to work, big deal.

What's the alternative? To have many similar commands

   ruby-find-implementation
   c++-find-implementations
   python-find-implementations
   js-find-implementations

that all do the same thing inside: call the Xref backend's "find 
implementations" mechanism? It will be especially great to use if some 
major mode authors bind that command to one key, and others to another.

> And Spencer even wanted to put cl-defgeneric in that bag, which I
> can fully understand, as cl-defgeneric can also be viewed as a
> declaration.  But its a completely different concept from those
> two.

If Elisp doesn't have any other kind of declarations, what is the worry? 
Let's put the ones it has.

Elisp's bag is different in that it will have separate kinds for 
faces/features/methods and, potentially, variables as well. But those 
are already in find-func.el and don't need new bindings.