Extract logic to gather deps added for <apex>:<module> pairs

Trades having to traverse a module's direct dependencies multiple times
for reusable code. While at the minute the amount of duplicated code is
small (checking a tag and appending to a list) follow up changes will
modify the gatherApexModulePairDepsWithTag module to improve error
reporting greatly increasing the benefit of deduping.

The cost of traversing a module's direct dependencies is very small as
there will be only a very few dependencies.

Bug: 177892522
Test: m nothing
Change-Id: I16389102abd8038e1bfa52b63f4153bdf92ff553

1 files changed, 15 insertions, 0 deletions

diff --git a/java/bootclasspath.go b/java/bootclasspath.go
index f1a0bb55c..02833ab66 100644
--- a/java/bootclasspath.go
+++ b/java/bootclasspath.go
@@ -73,6 +73,8 @@ func addDependencyOntoApexVariants(ctx android.BottomUpMutatorContext, propertyN
 // module. This adds dependencies onto the prebuilt and source modules with the specified name,
 // depending on which ones are available. Visiting must use isActiveModule to select the preferred
 // module when both source and prebuilt modules are available.
+//
+// Use gatherApexModulePairDepsWithTag to retrieve the dependencies.
 func addDependencyOntoApexModulePair(ctx android.BottomUpMutatorContext, apex string, name string, tag blueprint.DependencyTag) {
 	var variations []blueprint.Variation
 	if apex != "platform" && apex != "system_ext" {
@@ -118,6 +120,19 @@ func reportMissingVariationDependency(ctx android.BottomUpMutatorContext, variat
 	ctx.AddFarVariationDependencies(variations, nil, name)
 }
 
+// gatherApexModulePairDepsWithTag returns the list of dependencies with the supplied tag that was
+// added by addDependencyOntoApexModulePair.
+func gatherApexModulePairDepsWithTag(ctx android.BaseModuleContext, tag blueprint.DependencyTag) []android.Module {
+	var modules []android.Module
+	ctx.VisitDirectDepsIf(isActiveModule, func(module android.Module) {
+		t := ctx.OtherModuleDependencyTag(module)
+		if t == tag {
+			modules = append(modules, module)
+		}
+	})
+	return modules
+}
+
 // ApexVariantReference specifies a particular apex variant of a module.
 type ApexVariantReference struct {
 	// The name of the module apex variant, i.e. the apex containing the module variant.