[PATCHv5,2/2] pkg-generic: improve incorrectly used package detection

The package infrastructure now detects when a target package is being
built even if its corresponding Config.in option is not enabled, and
aborts with an error. However, it does not indicate *which* package is
improperly depending on the current package without selecting it at
the kconfig level.

So, in this commit, in addition to displaying an error, we try to help
the user by saying which packages could be the culprit. To achieve
this, we register the reverse dependencies of each package in a
variable called <pkg>_DEPENDENT_OF, and display this variable for the
problematic package when the error is detected. Many thanks to Yann
E. Morin for the idea and implementation!

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
 package/pkg-generic.mk | 8 ++++++++
 1 file changed, 8 insertions(+)

Thomas, All,

On 2015-10-09 11:15 +0200, Thomas Petazzoni spake thusly:
> The package infrastructure now detects when a target package is being
> built even if its corresponding Config.in option is not enabled, and
> aborts with an error. However, it does not indicate *which* package is
> improperly depending on the current package without selecting it at
> the kconfig level.
> 
> So, in this commit, in addition to displaying an error, we try to help
> the user by saying which packages could be the culprit. To achieve
> this, we register the reverse dependencies of each package in a
> variable called <pkg>_DEPENDENT_OF, and display this variable for the
> problematic package when the error is detected. Many thanks to Yann
> E. Morin for the idea and implementation!
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> ---
>  package/pkg-generic.mk | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
> index a831199..1266a47 100644
> --- a/package/pkg-generic.mk
> +++ b/package/pkg-generic.mk
> @@ -150,6 +150,8 @@ ifeq ($(MAKECMDGOALS),)
>  	@if test "$($(PKG)_TYPE)" = "target" -a -z "$($($(PKG)_KCONFIG_VAR))" ; then \
>  		echo "ERROR: A package must have added $($(PKG)_NAME) to its _DEPENDENCIES line but" ; \
>  		echo "forgot to add the corresponding select / depends on $($(PKG)_KCONFIG_VAR)." ; \
> +		echo "Potential culprits:" ; \
> +		for p in $($(PKG)_DEPENDENT_OF) ; do echo " - $$p" ; done ; \

This does only work for first-level culprits.

For example, I added;
    BUSYBOX_DEPENDENCIES += exim

And I get:

    >>> berkeleydb 5.3.28 Patching libtool
    ERROR: A package must have added berkeleydb to its _DEPENDENCIES line but
    forgot to add the corresponding select / depends on BR2_PACKAGE_BERKELEYDB.
    Potential culprits:
    make[1]: *** [.../berkeleydb-5.3.28/.stamp_configured] Error 1
    make: *** [_all] Error 2

That's because the real culprit is not directly the cause of the
berkeleydb dependency; the depenency chain is two-or-more levels deep.

So, NAK on this patch (even though that was my idea originally, IIRC).

I'll (later!) to find a solution...

Regards,
Yann E. MORIN.

>  		exit 1 ; \
>  	fi
>  endif
> @@ -777,6 +779,12 @@ endif # ifneq ($$(call qstrip,$$($(2)_SOURCE)),)
>  # configuration
>  ifeq ($$($$($(2)_KCONFIG_VAR)),y)
>  
> +# Store reverse build-dependency information: we add the name of the
> +# current package to the <pkg>_DEPENDENT_OF variable of all packages
> +# the current package depends on.
> +$$(eval $$(foreach d,$$($(2)_FINAL_ALL_DEPENDENCIES),\
> +	$$(call UPPERCASE,$$(d))_DEPENDENT_OF += $(1)$$(sep)))
> +
>  # Ensure the calling package is the declared provider for all the virtual
>  # packages it claims to be an implementation of.
>  ifneq ($$($(2)_PROVIDES),)
> -- 
> 2.6.1
> 
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