Re: progmodes/project.el and search paths

[Dmitry Gutov]

Hi Eric,

Sorry for the late reply. I wasn't really sure what kind of response is 
expected.

In short, I like your vision as a whole, but whether each particular 
element of it can apply to project.el, should be investigated separately.

On some of them:

* I wonder what's the main use of having hierarchical projects vs. 
simply tracking several currently open projects (or project roots). And 
how the consumers of the API would take advantage of that distinction.

* Project services seem to be the proper way to handle optional traits 
of significant size that some projects have, and others don't.

* "Project Loading safety" are probably out of scope. I'd expect the 
majority of implementations to be based around loading a project build 
(or settings) file of pre-existing format. The popular IDEs don't ask 
the user whether they want to load the project file. On the other hand, 
some project types might need to be enabled/visited explicitly.

* WRT "Detection ordering", the current project-find-functions structure 
might be enough. Any Makefile project implementation will most likely go 
before the VC project anyway (unless the respective add-hook form is 
told to APPEND, for some reason). And it's hard for us to expect for 
third-party implementations to be able to declare priorities between 
themselves.

* "Update meta-data" might be handled by each respective implementation, 
in conjunction with auto-revert-mode.

* "Project browsing" shouldn't need much more than project.el exposes 
already.

* "Project Local Variables" look very similar to project metadata.

* The "'include path' concept" looks very similar to 
project-search-path. This might be the main purpose for the 
project-search-path entries that lie within project-roots.

* WRT cscope, etc, integration, I think the main unsolved problem we 
currently have is that they aren't re-run automatically. Nor do we have 
a command that would do that for the user on demand.

* "Load a project" seems incompatible with the project-find-functions 
approach. Which is unfortunate.

* "navigating between code and doc", as stated, doesn't seem 
particularly useful: if you're reading the source code of a function, 
the docstring is usually right above. Jumping from the doc to the source 
is better, but this is closer to the domain of xref.

* "Language specificity" might be useful, but in practical terms it 
sounds like adding an optional (?) "language" argument to 
project-search-path and any similar method that we add later. Which 
complicates implementations. Or just have an Emacs-global repository of 
file name patterns corresponding to languages? Not sure.

* "commands specific to project implementations" could also be added by 
the minor modes supplied by the implementations' packages.

On 08/05/2015 04:29 AM, Eric Ludlam wrote:

> Emacs has a lot of tools that could use a project service, and sometimes
> all the tool needs is a small push of convenience, and not full project
> management system.  A generic project system will make it easy to add
> small conveniences in lots of places you may not expect because tool
> authors will feel safe using it.

That's the idea, yes.

> The attached is my experience of things I either needed in EDE's base
> classes to implement a project, or that some tool needed, and what I
> learned along the way.  You might think it is too EDE specific,

I wouldn't say the majority of items in the list are EDE specific.

> I consider this file incomplete, but I hope it proves useful as a
> starting point.  I'd be happy to periodically update it for a little
> while if it is useful.

Were we using a nice issue tracker, I'd have asked to create a tracking 
issue (or would've created one myself), but in the present situation, I 
guess you'll have to resend it with updates.

But in any case, I'd say technical proposals on specific features, as 
well as patches, would provide more value here, rather than maintaining 
a high-level overview of things we might get around to someday.