[OE-core] Passing additional data from packages to be used during image creation

[Pascal Bach]

On 21.01.2017 12:44, Richard Purdie wrote:
> On Thu, 2017-01-19 at 10:16 +0100, Pascal Bach wrote:
>> I would like to pass some additional data generated during the
>> creation of a package to the image creation step.
>> The idea is to use this data to generate a more detailed manifest of
>> what is included in the image. In the concrete case
>> I would like to pass a list of required copyright files that need to
>> be checked for during image creation.
>>
>> My current approach is to add this list as a new variable COPYRIGHTS
>> to the pkgdata of each package.
>> Using the image manifest to determine the package this allows me to
>> compile a list of all required copyrights.
>>
>> The following patch allows to add extra variables to pkgdata and thus
>> allows to pass additional data
>>
>> - [PATCH] package.bbclass: allow additional variables to be added to
>>
>> Is this a valid approach or did a miss a simpler way to access any
>> package data during image creation?
> I'm curious if adding something to PACKAGEVARS would work or if not,
> why not?
Just adding it to PACKAGEVARS is not enough as the list of variables written to the pkgdata files is hard coded in emit_pkgdata here: https://github.com/openembedded/openembedded-core/blob/master/meta/classes/package.bbclass#L1365

However I notices an issue with the code as it seams the do_package step is not triggered if a variable in PACKAGE_EXTRA_PKGDATA changes. I'm not sure why as it should be
added as a vardeps to the do_package task. For example if I add "COPYRIGHTS" to PACKAGE_EXTRA_PKGDATA and than change the COPYRIGHTS variable in a recipe the do_package step doesn't get executed.
I'm trying to figure out why but if somebody can spot what I did wrong this would be appreciated.

Pascal