Re: [gentoo-dev] RFD: EAPI specification in ebuilds

[Brian Harring <ferringb@gmail.com>]

On Sat, Mar 10, 2012 at 08:06:50AM -0800, Zac Medico wrote:
> On 03/09/2012 11:20 AM, Ciaran McCreesh wrote:
> > On Fri, 09 Mar 2012 11:49:44 -0500
> > Michael Orlitzky <michael@orlitzky.com> wrote:
> >>>> isnt the whole point of the proposal to get eapi without sourcing ?
> >>>>
> >>>> so that we can use new bash features at local or global scope
> >>>> without risking that people with an old bash get syntax errors
> >>>> trying to get the eapi
> >>>
> >>> Right. Michael has lost sight of the goal and is moving off on a
> >>> tangent.
> >>
> >> The point was to be able to get the EAPI without crashing if the
> >> ebuild uses newer features.
> > 
> > No, it's not. There's more to it than that.
> > 
> > Some EAPIs really require defining certain environment variables, shell
> > options, sandbox things etc *before* the sourcing starts. It's a massive
> > pain in the ass to try to handle setting that kind of thing on the fly
> > once the sourcing has already started. Knowing the EAPI before having
> > to spawn a bash process isn't just about performance, it's also about
> > making ebuilds much less difficult to deal with.
> 
> Yeah. Another way of putting it is that the requirement to spawn a bash
> process and source the ebuild adds a ridiculous amount of unnecessary
> complexity, in violation of the KISS principle [1].

This statement is incorrect.

Even if EAPI could be parsed via some non sourcing approach, we 
*still* have to source the ebuild to get the metadata for when the 
EAPI is supported (the vast majority of usage).  That complexity is 
there one way or another- we wouldn't be trying to extract the EAPI 
from the ebuild unless the cache was invalid/missing.

Phrasing it more bluntly: you can only avoid the sourcing step if you 
can isolate that the EAPI is unsupported (which is extremely rare in 
terms of actual user experience).  For the rest of the time (well past 
the 99% mark) sourcing is the immediate step following.


Also, stop referencing wikipedia.  People know what "trivial 
objection" and "KISS" is.  Pointing at random wikipedia links when
people object is just a form of fallacious argument from authority 
( http://en.wikipedia.org/wiki/Argument_from_authority ). :P

~brian