Re: Subprojects in project.el

[Dmitry Gutov <dgutov@yandex.ru>]

On 26/11/22 11:23, João Távora wrote:
> Dmitry Gutov <dgutov@yandex.ru> writes:
> 
>> On 26/11/22 02:00, João Távora wrote:
> 
>> We aren't even close to top efficiency WRT file operations now. And
>> your idea is also based on hand-crafting project-find-functions to
>> only contain the necessary items.
> 
> project-find-functions is part of project.el's API.  So it makes a lot
> of sense to use, otherwise why would it be there?  We can provide some
> pre-baked functions to put there, or already put there for users.  The
> key point is that functions bail out early if they don't the adequate
> context.  One of them is the one I proposed earlier, which uses a local
> project-subproject-prefixes variable.  Another would search for marker
> files and consult a tramp-specific user variable for opt-out.

project-find-functions up until now has worked like many other hooks we 
have (e.g. completion-at-point-functions): the first element that 
returns non-nil is used, the others are not paid attention.

That allows these hooks to be used by major and minor modes, rather than 
having the user curate the full list. As long as priorities are set 
correctly, the system works. E.g. projectile-mode can just add its own 
element at the beginning, and not worry about stuff that already exists 
there.

>> As opposed to real-life scenario of Projectile just adding its
>> function at the front.
>>
>>>> I don't entirely understand the algorithm you're proposing here, but
>>>> it sounds vaguely like what I'm writing now, so you might like the
>>>> result.
>>> Where/when can I find this code?
>>
>> You and others can now find it here: https://debbugs.gnu.org/41572#186
> 
> That thread has a latest patch that allows marker files to designate
> top-level projects: I'm not interested in using marker files
> specifically, so I don't see the relevance.  I can't deduce from the
> patch what you're trying to solve or if it solves my use case.

Previously you said:

 > Fwiw, Danny's tip is what I used at a recent day job gig for defining 
subprojects in a 400k files repo.

where Danny's snippet looked like:

   (defun project-find-project.el (dir)
     "Returns a `manual-project' instance if the project of the current
   DIR has a .project.el file in its root directory."
     (let ((root (locate-dominating-file dir ".project.el")))
       (when root
         (cons 'transient root))))

   (add-hook 'project-find-functions #'project-find-project.el)

...but you didn't use marker files? Or you don't want to use them 
anymore? I'm really confused here.