Add java_system_modules to sdk/module_exports

Adds an SdkMemberType implementation for java_system_modules. It
specifies that java_system_modules can be used with sdk as well as
module_exports, and also that the libs property should be included
as transitive members in the sdk.

It also adds support for treating appropriate tagged properties in
the snapshot prebuilts module as references to sdk members so that
they are correctly transformed when creating the versioned modules.

Bug: 142940300
Test: m nothing
Change-Id: Ic10b5a6d5b92b6018334fe876f06feaf79cc55e9
diff --git a/java/system_modules.go b/java/system_modules.go
index 92297c4..731503f 100644
--- a/java/system_modules.go
+++ b/java/system_modules.go
@@ -31,6 +31,15 @@
 	RegisterSystemModulesBuildComponents(android.InitRegistrationContext)
 
 	pctx.SourcePathVariable("moduleInfoJavaPath", "build/soong/scripts/jars-to-module-info-java.sh")
+
+	// Register sdk member types.
+	android.RegisterSdkMemberType(&systemModulesSdkMemberType{
+		android.SdkMemberTypeBase{
+			PropertyName:         "java_system_modules",
+			SupportsSdk:          true,
+			TransitiveSdkMembers: true,
+		},
+	})
 }
 
 func RegisterSystemModulesBuildComponents(ctx android.RegistrationContext) {
@@ -66,6 +75,10 @@
 		},
 	},
 		"classpath", "outDir", "workDir")
+
+	// Dependency tag that causes the added dependencies to be added as java_header_libs
+	// to the sdk/module_exports/snapshot.
+	systemModulesLibsTag = android.DependencyTagForSdkMemberType(javaHeaderLibsSdkMemberType)
 )
 
 func TransformJarsToSystemModules(ctx android.ModuleContext, jars android.Paths) (android.Path, android.Paths) {
@@ -107,6 +120,7 @@
 type SystemModules struct {
 	android.ModuleBase
 	android.DefaultableModuleBase
+	android.SdkBase
 
 	properties SystemModulesProperties
 
@@ -125,7 +139,7 @@
 func (system *SystemModules) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 	var jars android.Paths
 
-	ctx.VisitDirectDepsWithTag(libTag, func(module android.Module) {
+	ctx.VisitDirectDepsWithTag(systemModulesLibsTag, func(module android.Module) {
 		dep, _ := module.(Dependency)
 		jars = append(jars, dep.HeaderJars()...)
 	})
@@ -136,7 +150,7 @@
 }
 
 func (system *SystemModules) DepsMutator(ctx android.BottomUpMutatorContext) {
-	ctx.AddVariationDependencies(nil, libTag, system.properties.Libs...)
+	ctx.AddVariationDependencies(nil, systemModulesLibsTag, system.properties.Libs...)
 }
 
 func (system *SystemModules) AndroidMk() android.AndroidMkData {
@@ -173,6 +187,7 @@
 	android.InitPrebuiltModule(module, &module.properties.Libs)
 	android.InitAndroidArchModule(module, android.HostAndDeviceSupported, android.MultilibCommon)
 	android.InitDefaultableModule(module)
+	android.InitSdkAwareModule(module)
 	return module
 }
 
@@ -188,3 +203,37 @@
 func (system *systemModulesImport) Prebuilt() *android.Prebuilt {
 	return &system.prebuilt
 }
+
+type systemModulesSdkMemberType struct {
+	android.SdkMemberTypeBase
+}
+
+func (mt *systemModulesSdkMemberType) AddDependencies(mctx android.BottomUpMutatorContext, dependencyTag blueprint.DependencyTag, names []string) {
+	mctx.AddVariationDependencies(nil, dependencyTag, names...)
+}
+
+func (mt *systemModulesSdkMemberType) IsInstance(module android.Module) bool {
+	if _, ok := module.(*SystemModules); ok {
+		// A prebuilt system module cannot be added as a member of an sdk because the source and
+		// snapshot instances would conflict.
+		_, ok := module.(*systemModulesImport)
+		return !ok
+	}
+	return false
+}
+
+func (mt *systemModulesSdkMemberType) BuildSnapshot(sdkModuleContext android.ModuleContext, builder android.SnapshotBuilder, member android.SdkMember) {
+	variants := member.Variants()
+	if len(variants) != 1 {
+		sdkModuleContext.ModuleErrorf("sdk contains %d variants of member %q but only one is allowed", len(variants), member.Name())
+		for _, variant := range variants {
+			sdkModuleContext.ModuleErrorf("    %q", variant)
+		}
+	}
+	variant := variants[0]
+	systemModule := variant.(*SystemModules)
+
+	pbm := builder.AddPrebuiltModule(member, "java_system_modules_import")
+	// Add the references to the libraries that form the system module.
+	pbm.AddPropertyWithTag("libs", systemModule.properties.Libs, builder.SdkMemberReferencePropertyTag())
+}