bug#69584: 29.2.50; project-find-functions should have access to maybe-prompt

[Dmitry Gutov <dmitry@gutov.dev>]

On 02/04/2024 20:54, Spencer Baugh wrote:
> Spencer Baugh <sbaugh@janestreet.com> writes:
>> So when you open up a branch overview, you'll usually assume there's a
>> local copy, and so your first action will probably some command which
>> uses project-current.  But if there's no working copy, then you'll get
>> dropped to a prompt to choose a project, instead of (say) a
>> project-find-file prompt, which you might not immediately notice, which
>> is confusing, and you'll have to C-g out of it, and then run some other
>> command to create the working copy.  All that is a hassle.
> 
> Oh, I've thought of a different resolution to this which may be better.
> 
> When project-current fails to find a project in default-directory, if
> maybe-prompt=t, project-current will run project-prompter.
> 
> So I can just have a buffer-local project-prompter in the branch
> overview buffer.  And that project-prompter knows it's in a branch
> overview buffer, and can prompt "Would you like to make a working copy
> for [some branch]?".
> 
> That's elegant and doesn't change the semantics of project-current at
> all: project-prompter already can return an arbitrary directory.
> 
> Except... I suppose this would make project-switch-project behave worse,
> because hitting C-x p p in a branch overview buffer would now prompt to
> create a working copy for that branch, when what you probably want to do
> is switch to a different project entirely.
> 
> I guess there are two use cases for project-prompter: one is "fallback
> for project-current" and the other is "switch to a different project".
> Maybe we could support them being different?

I'm not sure how we'd do that. A new, optional, argument to 
project-prompter? Two different variables?

Right now we have two well-defined steps:

- Run a hook, where the current project can be detected,
- Or call the prompter, which will let the user choose a project 
manually (from the history, or from the file system).

That helps the prompter have a compact, focused interface. If it can 
also ask about other things, that makes things more complicated.

But for your own system, I suppose you could implement the described 
workflow right now with the current tools, using add-function: your 
project-find-functions element would itself return nil but add an 
around-advice for project-prompter, which would do more work, prompt the 
user, and ultimately return the intended object. And remove the advice 
as the first step, of course. What could require further testing - is 
the scenario where the prompter is called twice (when you invoke 
project-switch-project), but it'll probably work too, since the calls 
are not recursive.

To take a step back, I wonder if you have tried using the newly added 
binding for 'non-essential' yet. It seems like it should allow a simpler 
implementation.