Re: Opaque objects and Emacs documentation

[Dmitry Gutov <dgutov@yandex.ru>]

On 21.07.2020 17:34, Eli Zaretskii wrote:
> So the type returned by each hook could
> be documented in the doc string of that hook in terms suggested by
> Richard (or something similar).

It could. It would not be a significant problem.

> Similarly, the "transient" project instance returned by
> project-current itself, when a project doesn't yet exist, is also
> known, and its structure could be similarly documented without
> impediment to extensibility.

If you say that, could you give an example of something that *would* be 
an impediment to extensibility? I'd like to see where we stand now.

> Whether the structure is obvious from the implementation may or may
> not be true (and the author of the code is usually not the best judge
> of that), but doesn't solve the issue at hand, IMO.

So have we moved on from trying to document the examples in the 
docstrings of project-find-functions or project-current?

> A good
> documentation of an interface should allow a developer to write code
> that uses the interface without looking at the interface's
> implementation.

Right. But there won't be any third-party callers of project-try-vc, 
this function's only purpose is to be inside project-find-functions.

Or at least there shouldn't be any until we're reasonably certain we 
want to support it as a public function, and we understand in what 
circumstances it might be called.

So as things currently stand, the responsibility for it being correct 
and accepting the right argument lies on its author, and not on any 
third-party developers.

> If it is necessary to consult the implementation,
> that is an indication of some deficiency in the docs, and we should
> try to avoid that as much as possible.

No disagreement there, as long as we're talking about public functions.