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

[Zac Medico <zmedico@gentoo.org>]

On 03/09/2012 09:31 AM, Michael Orlitzky wrote:
> On 03/09/12 12:11, Ulrich Mueller wrote:
>>>>>>> On Fri, 09 Mar 2012, Michael Orlitzky wrote:
>>
>>>> What if bash starts to parse the script completely and barfs at
>>>> 'syntax error' before it starts executing stuff?
>>
>>> It doesn't parse the script completely, it executes line-by-line, so
>>> we can bail out early.
>>
>> How can you tell that this behaviour won't be changed in a future bash
>> version?
>>
> 
> Who's to say that in the future my computer won't be made out of
> delicious ice cream, eliminating the need for EAPIs entirely?
> 
> Chances are, this would break thousands of scripts, so we hope they
> wouldn't do it. If it does happen, we either deal with it then, or don't
> upgrade to that version of bash -- the same as we would do with any
> other massive breaking change.

Ulrich is talking about extensions which require a newer version of
bash. These kinds of extensions are quite common and don't cause
"massive breaking" because people simply have to upgrade bash in order
to use the new extensions, and their old scripts continue to run because
the new extensions don't interfere with backward compatibility.

Your eapi() function proposal is especially fragile in this context
because it assumes that the installed version of bash will be able to
execute a script that may target a newer version of bash. This is a
special case that is typically not a problem, although it is a major
problem under the specific conditions that your eapi() function approach
induces.

Anyway, lets focus on our main goal, which is to decide on a way to
obtain the EAPI _without_ sourcing the ebuild.
-- 
Thanks,
Zac