[OE-core] [PROPOSAL] Package feature switches, redux.

[Richard Purdie]

On Mon, 2011-07-04 at 12:54 +0100, Chris Elston wrote:
> Since responses to my previous mail were generally positive, I've
> reworked the package feature switches so that the interface is as RP
> suggested.
> 
> In the recipe for foo you would have a set of features defined like
> this:
> 
> PACKAGE_CONFIG[bar] = "--enable-bar, --disable-bar, libbar"
> PACKAGE_CONFIG[baz] = "--enable-baz, --disable-baz, libbaz"
> 
> The default set of features for the package would be defined with:
> 
> PACKAGE_FEATURES ?= "bar baz" 
> 
> Perhaps this set of features could go into a metadata field in the .ipk
> - would this be helpful for feed users?
> 
> The package features can then be tailored in a config/layer with
> something like:
> 
> PACKAGE_FEATURES_pn-foo = "baz pop"
> 
> If a layer requests a feature not supported by the recipe, you get a
> warning (should help distro maintainers detect bitrot in their layer):
> 
> WARNING: foo: Unknown feature 'pop' requested
> 
> The patch below uses gstreamer as an example of something which would
> benefit from this:

Looks good, thanks.

My main concern is still the PACKAGE_FEATURES variable. I've been
meaning to reply to your original email about this.

I understand your issue that you want to be able to do this on a per
package basis. I suspect you also see my concern about maintain this
centrally as a distro decision primarily rather than letting things
descend into more of a free for all.

FWIW, even if done centrally using DISTRO_FEATURES, you can customise on
a per recipe basis if you ever needed to, e.g.:

DISTRO_FEATURES = "a b c ${MYDISTROTWEAKS}"
MYDISTROTWEAKS = "d e f"
MYDISTROTWEAKS_pn-gstreamer = "e"

Now I'd agree this is a bit ugly but I think it would encourage less
misuse of the variable.

Any thoughts on that?

Cheers,

Richard