[webkit-dev] RFC: Removing feature flag defaults in build-webkit

[Tim Horton]

> On Sep 21, 2017, at 11:57, Konstantin Tokarev <annulen at yandex.ru> wrote:
> 
> 
> 
> 21.09.2017, 21:54, "Tim Horton" <timothy_horton at apple.com>:
>> Hi, all!
>> 
>> Would anybody mind if build-webkit stopped being a source of default values of feature flags?
>> 
>> We have defaults for feature flags in FeatureDefines.xcconfig for Xcode, WebKitFeatures.cmake (and Options*.cmake for platform overrides) for CMake, and FeatureDefines.h for everyone. This is already a mess. But it gets worse!
>> 
>> Right now, for both the Xcode and CMake builds, build-webkit overrides those with its own set of defaults (in FeatureList.pm). There is also currently an argument to fall back to the CMake defaults (--default-cmake-features) and ignore build-webkit’s defaults.
>> 
>> It doesn’t make sense that build-webkit enables a different set of features than a plain ol’ ‘xcodebuild’ or ‘cmake’ in the root directory. It seems like we’ve mostly tried to keep them in sync, but that’s silly busywork for seemingly little benefit.
>> 
>> If we do this, the effective changes would be as follows:
>> 
>>> 1) The default values of feature flags would be specified in all of the usual places except FeatureList.pm
>>> 2) build-webkit --help will no longer list the default value of feature flags
>>> 3) It will be easier (but still not easy, yet) to reason about the default value of feature flags, and keep them in sync between different ways people build
>>> 4) --default-cmake-features will go away, because it will always be true
>> 
>> And things that wouldn’t change:
>> 
>>> 1) You will still be able to use --FEATURE, --no-FEATURE, and --minimal arguments to build-webkit
>> 
>> Any objections or things I’ve overlooked?
> 
> I think it would be more useful to have a single file (e.g. JSON) with options and their default values, and  generate all other lists from it.

I agree, but it is a much, much bigger project to get us to 1 list than to reduce us by 1 list.

>> 
>> —Tim
>> ,
>> 
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> 
> 
> -- 
> Regards,
> Konstantin