Re: project.el semantics

[Dmitry Gutov]

On 11/13/2015 12:04 AM, Dmitry Gutov wrote:

> Please feel free to submit a patch across these lines (adding
> project-metadata). It might be moot now, given that John decided to pull
> project.el from Emacs 25.1, but it could at least serve as a point of
> comparison for his project API proposal.

Scratch that. John and I had a chat, and it seems project.el has a 
chance in Emacs 25.1, provided it's changed along the lines we've been 
discussing here.

I've had some thoughts since.

Some minor things:

- We'll probably want to rename `project-roots' to 
`project-directories'. Even though they'll be treated like "roots" 
(traversed recursively) most of the time, a project backend can return 
different kinds of directories in this list, including certain 
subdirectories of the project root(s).

For instance, in can include the test roots in there. Or, I don't know, 
some other kinds of directories that aren't supposed to be traversed 
recursively.

- If we're only documenting the "categories" key inside 
project-metadata, why not have a project-directory-categories method 
instead? We can add the -metadata method, too, now or later.

- What's the category name for the directories that are the project 
roots in the current interpretation? Internal?

Bigger one:

- If each directory is supposed to be categorized, and the set of 
categories is flexible, what's going to be the counterpart to 
`project-library-roots-function'?

Do we call it project-roots-function, and allow it to return a list of 
uncategorized strings, which each project-directories impl must merge in?

Or do we allow a new variable which would return a buffer-local project 
(adhering to the same API), which the "real" project would delegate to?

Alternatively, I'm inclined to mix the first option with demoting 
project-roots-function to project-vc-directories (a mixed list of 
strings and functions). One fewer wart in the API, and the list would be 
directory-local, instead of buffer-local.

We can also mix 2 and 3 (project-vc-directories might contain 
language-specific backends, as well as strings), but that's probably too 
weird.