[LEDE-DEV] [PATCH] metadata: compile dependencies only when the package is selected

[Yousong Zhou]

On 2 March 2018 at 17:19, Felix Fietkau <nbd at nbd.name> wrote:
> On 2018-03-02 10:07, Yousong Zhou wrote:
>> On 1 March 2018 at 17:36, Felix Fietkau <nbd at nbd.name> wrote:
>>> To give you a better example, I just took another look at our packages
>>> and found one that would directly be affected by your change:
>>>
>>> Take a look at libs/elektra/Makefile in packages.git
>>> It has various plugins with their own dependencies.
>>> One depends on boost, one on python, one on openssl, etc.
>>> No PKG_BUILD_DEPENDS or PKG_CONFIG_DEPENDS.
>>>
>>> Let's run the same scenario as above:
>>> - do a clean build with just libelektra-core selected
>>> - select libelektra-boost and run make again
>>>
>>> Now there's two possibilities. Either the build fails on the first round
>>> already, because the package was expecting to be built with boost, which
>>> isn't available.
>>> Or, the build fails on the second round because the first one had built
>>> elektra without the boost plugins and there's nothing that triggers a
>>> rebuild.
>>
>> I see.  I can fix the 2nd case by letting STAMP_CONFIGURED depend on
>> selection state of subpackages.  It's indeed pain if packagers need to
>> guess whether they should put each CONFIG_PACKAGE_xx symbol into
>> PKG_CONFIG_DEPENDS.
> That will not work in all cases. For some packages, using
> STAMP_CONFIGURED might not be enough (it might cache previous values).
> Different packages need different ways of dealing with this, which is a
> strong reason to not use this patch and keep the behavior opt-in (either
> via the existing conditional depend syntax, or by adding some new
> syntactic sugar).
>

Well, I thought for autotools we the autoreconf fixup can workaround
this, but it seems maybe the situation is just not that simple ;)

>> As for PKG_BUILD_DEPENDS, if any error happens it's not "random"
>> right?  Can we be more strict here by requiring packagers to put
>> correct values for this symbol?
> I don't know of any case where we need to add PKG_BUILD_DEPENDS, it
> could only serve as a workaround for breakage caused by your patch. But
> I don't think we should go that route.
>
> - Felix

Got it.  At least the current behaviour provides a consistent
configure environment for each package.  That's a good feature to
have.

Thanks,
                yousong