Add IsModulePreferred

Bug: 177892522
Test: m nothing
Change-Id: I47268b81359d6fceb60e899a730b3b6034e09814

android/prebuilt.go

@@ -213,6 +213,26 @@ type PrebuiltInterface interface {
 	Prebuilt() *Prebuilt
 }
 
+// IsModulePreferred returns true if the given module is preferred.
+//
+// A source module is preferred if there is no corresponding prebuilt module or the prebuilt module
+// does not have "prefer: true".
+//
+// A prebuilt module is preferred if there is no corresponding source module or the prebuilt module
+// has "prefer: true".
+func IsModulePreferred(module Module) bool {
+	if module.IsReplacedByPrebuilt() {
+		// A source module that has been replaced by a prebuilt counterpart.
+		return false
+	}
+	if prebuilt, ok := module.(PrebuiltInterface); ok {
+		if p := prebuilt.Prebuilt(); p != nil {
+			return p.UsePrebuilt()
+		}
+	}
+	return true
+}
+
 func RegisterPrebuiltsPreArchMutators(ctx RegisterMutatorsContext) {
 	ctx.BottomUp("prebuilt_rename", PrebuiltRenameMutator).Parallel()
 }

java/boot_jars.go

@@ -56,16 +56,7 @@ func isActiveModule(module android.Module) bool {
 	if !module.Enabled() {
 		return false
 	}
-	if module.IsReplacedByPrebuilt() {
-		// A source module that has been replaced by a prebuilt counterpart.
-		return false
-	}
-	if prebuilt, ok := module.(android.PrebuiltInterface); ok {
-		if p := prebuilt.Prebuilt(); p != nil {
-			return p.UsePrebuilt()
-		}
-	}
-	return true
+	return android.IsModulePreferred(module)
 }
 
 func (b *bootJarsSingleton) GenerateBuildActions(ctx android.SingletonContext) {

java/platform_compat_config.go

@@ -232,15 +232,7 @@ func isModulePreferredByCompatConfig(module android.Module) bool {
 		}
 	}
 
-	// A prebuilt module should only be used when it is preferred.
-	if pi, ok := module.(android.PrebuiltInterface); ok {
-		if p := pi.Prebuilt(); p != nil {
-			return p.UsePrebuilt()
-		}
-	}
-
-	// Otherwise, a module should only be used if it has not been replaced by a prebuilt.
-	return !module.IsReplacedByPrebuilt()
+	return android.IsModulePreferred(module)
 }
 
 func (p *platformCompatConfigSingleton) GenerateBuildActions(ctx android.SingletonContext) {