Re: Unified project interface

[Dmitry Gutov]

On 07/11/2015 04:43 PM, Bozhidar Batsov wrote:
> I finally took a quick look at the current code (and the discussion so
> far) and I have a few remarks:
>
> * even within source directories it's useful to be able to exclude
> certain subdirs from project-level operations. How is this going to be
> handled?

A new function (or two?) will be needed for that. Is there a particular 
reason Projectile has both ignored-directories and ignored-files?

I'm also undecided on what it (or they) should return. Should that be 
just a list of shell globs? That would integrate fine with grep-find.

It also has both grep-find-ignored-directories and 
grep-find-ignored-directories. I wonder if that was done for performance.

> * it's not 100% clear to me what are major mode writes supposed to
> provide as "project implementations"

major modes aren't really supposed to. Since the current project is 
dependent on the directory and not a specific files, it's best left to 
minor modes.

An implementation is a new project-find-functions element and a set of 
cl-defmethod forms to go with it. Maybe also a cl-struct definition for 
the project structure, but as you can see from the current project.el 
contents, you can do without it.

> * In 24.4 a `vc-root-dir` was added. Seems it overlaps a bit with
> `project.el`

Only if the project is based on VC. As you can see project-try-vc uses 
that backend action, if not the function itself.

> * how can Projectile (or a similar package) leverage `project.el`?

Do something along these lines:

(defun project-try-projectile ()
  (when (projectile-project-root) 'projectile)

(add-hook 'project-find-functions #'project-try-projectile)

(cl-defmethod project-root (project (eql projectile))
  (projectile-project-root))

...and so on.

The first difficulty will be that cl-generic (and hence, cl-defmethod) 
are unavailable in the previous Emacs versions. Maybe put all this in a 
separate file and (require ...) it conditionally on the Emacs version.