Re: Subprojects in project.el (Was: Eglot, project.el, and python virtual environments)

[Dmitry Gutov]

On 24/11/22 10:42, João Távora wrote:
> On Thu, Nov 24, 2022 at 2:49 AM Dmitry Gutov <dgutov@yandex.ru 
> <mailto:dgutov@yandex.ru>> wrote:
>
>     On 23/11/22 22:33, João Távora wrote:
>      > For my idea to work, project-current would have to be changed to
>      >
>      > 1. Call all members of project-find-functions: return the innermost
>      >     project found thus far.
>      > 2. Not call project-find-functions recursively when called from
>     within a
>      > function
>      >     in project-find-functions, just return the innermost project
>     found
>      >     thus far.
>      >
>      > I don't see any big performance problems in this alternative.
>
>     Might not be much of a difference in a simple configuration, but going
>     up and down dirs is not free even on a fast SSD, especially as the
>     number of the elements on this hook grows.
>
>     But where you will definitely see a difference, is when using this with
>     Tramp.
>
>
> Have you seen the code I posted? You'll notice that it doesn't do
> any file system operations, it just does file name operations. And
> those run in CPU/memory, not file system. So I cannot understand
> your argument.  But I am happy to measure performance in different
> scenarios, if you'd like to suggest a particularly problematic one.

I am commenting here on the idea to "Call all members of 
project-find-functions". Members of project-find-functions do file 
system operations.

And that's what your piece of code does (call all members):

+(defvar project--overriding-projects nil)
+
 (defun project--find-in-directory (dir)
-  (run-hook-with-args-until-success 'project-find-functions dir))
+  "Find projects that directory DIR belongs to.
+Return them as a list.  If more than one is found, the first is
+usually the innermost."
+  (or project--overriding-projects
+      (let (projects)
+        (run-hook-wrapped
+         'project-find-functions
+         (lambda (fn)
+           (let* ((project--overriding-projects projects)
+                  (prj (funcall fn dir)))
+             (when prj (push prj projects)))
+           nil))
+        projects)))