Merge ~sylvain-pineau/plainbox-provider-resource:fake_package_res_snappy into plainbox-provider-resource:master

[Sylvain Pineau]

See commit msg for details.

In short this patch makes the package resource to return at least one fake object on snappy.

[Jonathan Cave (jocave)]

It unblocks this particular case using the package resource, so I'm +1 for that.

It sounds like the expression is expecting to search a list of objects to test the expression. Would it not be reasonable to modify plainbox such that a resource job that "passed" but produced no resource objects returns a single "False" outcome rather causing the expression to fail?

review: Approve

[Sylvain Pineau (sylvain-pineau)]

From plainbox ctrl code:

When expressions fail then all the associated resources are
marked as failed since we don't want to get into the analysis
of logic expressions to know any "better".

https://git.launchpad.net/plainbox/tree/plainbox/impl/ctrl.py#n184

diff --git a/jobs/resource.pxu b/jobs/resource.pxu
index 41ea29d..fb5d173 100644
--- a/jobs/resource.pxu
+++ b/jobs/resource.pxu
@@ -121,7 +121,7 @@ id: package
 estimated_duration: 1.16
 plugin: resource
 command:
-    dpkg-query -W -f='name: ${Package}\nversion: ${Version}\nmodalias: ${Modaliases}\n\n' |\
+    dpkg-query -W -f='name: ${Package}\nversion: ${Version}\nmodalias: ${Modaliases}\n\n' || echo name: plainbox |\
     awk 'BEGIN {RS = ""; FS = "\n"}{print $1; print $2; if ($3 ~ /^modalias: .+$/) {print $3}; print "" }'
 _description: Generates a list of packages
 _summary: Collect information about installed software packages