Consider other locations when resolving IUs from updatesites

Currently the IULocation can only consider units from other locations if
these are also of type IU location but other target types might be able
to supply items in a way not know to the IULocation.

This adds the necessary infrastructure to support this usecase by using
the adapter pattern.

Fix #207

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/target/P2TargetUtils.java

@@ -32,11 +32,13 @@
 import java.util.WeakHashMap;
 import java.util.concurrent.ConcurrentHashMap;
 
+import org.eclipse.core.runtime.Adapters;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IPath;
 import org.eclipse.core.runtime.IProgressMonitor;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.MultiStatus;
+import org.eclipse.core.runtime.NullProgressMonitor;
 import org.eclipse.core.runtime.Platform;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.core.runtime.SubMonitor;
@@ -59,6 +61,7 @@
 import org.eclipse.equinox.p2.engine.spi.ProvisioningAction;
 import org.eclipse.equinox.p2.metadata.IArtifactKey;
 import org.eclipse.equinox.p2.metadata.IInstallableUnit;
+import org.eclipse.equinox.p2.metadata.IInstallableUnitQueryable;
 import org.eclipse.equinox.p2.metadata.IProvidedCapability;
 import org.eclipse.equinox.p2.metadata.IRequirement;
 import org.eclipse.equinox.p2.metadata.MetadataFactory;
@@ -1084,6 +1087,7 @@ private void resolveWithPlanner(ITargetDefinition target, IProgressMonitor monit
 		context.setProperty(ProvisioningContext.FOLLOW_REPOSITORY_REFERENCES, Boolean.toString(true));
 		context.setMetadataRepositories(getMetadataRepositories(target));
 		context.setArtifactRepositories(getArtifactRepositories(target));
+		context.setExtraInstallableUnits(getAdditionalProvisionIUs(target));
 
 		IProvisioningPlan plan = planner.getProvisioningPlan(request, context, subMonitor.split(20));
 		IStatus status = plan.getStatus();
@@ -1547,6 +1551,24 @@ private URI[] getMetadataRepositories(ITargetDefinition target) throws CoreExcep
 		return result.toArray(new URI[result.size()]);
 	}
 
+	private List<IInstallableUnit> getAdditionalProvisionIUs(ITargetDefinition target) {
+		List<IInstallableUnit> result = new ArrayList<>();
+		ITargetLocation[] containers = target.getTargetLocations();
+		if (containers != null) {
+			for (ITargetLocation container : containers) {
+				if (container instanceof IUBundleContainer) {
+					// this is already handled by getMetadataRepositories(..)
+					continue;
+				}
+				IInstallableUnitQueryable queryable = Adapters.adapt(container, IInstallableUnitQueryable.class);
+				if (queryable != null) {
+					queryable.query(QueryUtil.ALL_UNITS, new NullProgressMonitor()).forEach(result::add);
+				}
+			}
+		}
+		return result;
+	}
+
 	private static final String NATIVE_ARTIFACTS = "nativeArtifacts"; //$NON-NLS-1$
 	private static final String NATIVE_TYPE = "org.eclipse.equinox.p2.native"; //$NON-NLS-1$
 	private static final String PARM_OPERAND = "operand"; //$NON-NLS-1$