Re: Add cl-defgeneric project-name; first use case eglot

[Dmitry Gutov]

On 22/11/22 11:56, Kévin Le Gouguec wrote:

> > I don't see why the needs of Eglot usage justify another generic in
> > project.el, or should be solved in project.el to begin with.  If Dmitry
> > wants to add such a generic for his own reasons, with some future
> > development of project.el in mind, I won't object, of course.
>
> FWIW, being able to tell project.el "this project is named foobar,
> nevermind the path" would help me in a couple of situations:

I have just added (efe599df3127) a way to set the project name for VC 
backend through dir-locals.

Not sure if this way will be to your liking, but it's the most 
straightforward. Though I suppose we could also make this variable take 
an alist value, associating root dirs with names.

> (1) C-x p p emacs TAB is currently rather crowded, because I stuff a lot
> of things under ~/src/emacs: emacs.git worktrees, elpa.git, upstream
> repos for *ELPA packages…
>
> If I could "name" projects such that only emacs.git worktrees included
> the string "emacs" (rather than all repos under ~/src/emacs), that'd
> make completion more efficient.

You're welcome to experiment with project-prompt-project-dir's code. But 
note that until now that function didn't require to "materialize" 
project instances for every entry, it just works off saved directory names.

The feature you have in mind seems to require fetching a project 
instance for every dir and calling 'project-name' on it. The apparent #1 
gotcha would be with remote filesystems where connection is 
slow/impossible, but it might be possible to skip those when computing 
the names.

> (2) I'd like to be able to give nicknames to projects.  I could make
> project-prompt-project-dir use the flex style to match e.g. "fts" to
> "foo-testsuite", but I can think of other nicknames that wouldn't match
> (e.g. "xfoo" for "cross-foo").
>
> (3) I'd like to stick (project-name) in my frame-title-format; currently
> using "(file-name-base (directory-file-name (project-root
> (project-current))))", but my lack of creativity in worktree naming is
> biting me in the rear ("ah yes, the “master” project 😐").
>
> Granted, I would still need to come up with my own logic for more
> informative project names, but at least I could keep it separate from my
> frame-title-format logic.  E.g. if I had different project-naming
> conventions for $HOBBIES and $DAYJOB, I could keep frame-title-format in
> sync everywhere, but give different machines different project-naming
> code.
>
> Granted², I can already define my own indirection layer today; I don't
> need to wait for project-name to be introduced.
>
> (4) Similar itch with Magit buffer names:
>
> (info "(magit) Naming Buffers")
> https://magit.vc/manual/magit.html#Naming-Buffers
>
> Being able to stick a (project-name) in there (or a "%p") would be
> convenient, for the same reasons as frame-title-format: use the same
> Magit buffer-name config everywhere; keep project-naming logic
> "workplace-bound".

Cool. Hopefully the performance of 'project-current' won't make any of 
these applications unfeasible (like the mode-line which has to refresh 
after every change in any buffer, every keypress, etc).

> ISTM those look like "use-cases" for teaching project.el about "project
> names" untangled from project root paths.  I'd make use of that feature,
> regardless of what Eglot does.
>
> (Can't say whether a defgeneric is the most suited technical answer;
> FWIW I'd expect my project-naming code to look at various things,
> e.g. the project path, the repo's upstream URL, the current branch.  Not
> sure it matters much to me whether we use a defgeneric or a
> project-name-function, but then I'm not very familiar with generics)

The general design is we leave it up to the project implementations how 
to implement things internally. E.g. Projectile might already have its 
own way to specify the name. So we don't have any global vars which 
affect what all projects do.