Re: progmodes/project.el and search paths

[Eric Ludlam]

On 08/03/2015 06:47 PM, Dmitry Gutov wrote:
> > My
> > experience has been that tools that depend on a project to ask what the
> > current project is do so a lot.  As such, I cache the current project,
> > and current root project as buffer local variables.  Those project
> > structures then have relevant meta data as well.  Another tactic is
> > initializing each buffer into a project as it is created.  That moves
> > search time into a different timing that is less noticeable than
> > on-demand when the user makes a request.
>
> IME, (vc-call-backend backend 'root dir) takes a negligible amount of 
> time, so we might as well call it once per command. Of course, it 
> might be different when using Tramp, but both Tramp and VC do some 
> caching of their own. Other project implementations are free to employ 
> their own caching methods (might be buffer-local, or if the 
> implementation considers that only one project might be enabled at a 
> time, simply in its own variables). 

That is true now for project.el.  Once you support 20+ project 
definitions as in EDE where vc is just one of them, all that negligible 
time adds up.

Asking all 20+ project definitions to do their own caching is something 
EDE used to do, and it was a pain to maintain.  I recommend against it.

Eric