Create public stub for platform's sysprop_library

Java modules using SystemAPI can now link against platform owned
sysprop_library with public stub. This allows modules to use platform's
public sysprops (which should be regarded as an API) without any hidden
API usages, if using dynamic linking and boot class path.

This doesn't affect any vendor or odm owned sysprop_library.

Bug: 141246285
Bug: 145167888
Test: m
Change-Id: I99824fb24a75cc8282211c2ad6c6296ae9fca393

1 files changed, 60 insertions, 0 deletions

diff --git a/java/sysprop.go b/java/sysprop.go
new file mode 100644
index 000000000..1a70499b8
--- /dev/null
+++ b/java/sysprop.go
@@ -0,0 +1,60 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package java
+
+import (
+	"sync"
+
+	"android/soong/android"
+)
+
+type syspropLibraryInterface interface {
+	BaseModuleName() string
+	Owner() string
+	HasPublicStub() bool
+	JavaPublicStubName() string
+}
+
+var (
+	syspropPublicStubsKey  = android.NewOnceKey("syspropPublicStubsJava")
+	syspropPublicStubsLock sync.Mutex
+)
+
+func init() {
+	android.PreDepsMutators(func(ctx android.RegisterMutatorsContext) {
+		ctx.BottomUp("sysprop_java", SyspropMutator).Parallel()
+	})
+}
+
+func syspropPublicStubs(config android.Config) map[string]string {
+	return config.Once(syspropPublicStubsKey, func() interface{} {
+		return make(map[string]string)
+	}).(map[string]string)
+}
+
+// gather list of sysprop libraries owned by platform.
+func SyspropMutator(mctx android.BottomUpMutatorContext) {
+	if m, ok := mctx.Module().(syspropLibraryInterface); ok {
+		if m.Owner() != "Platform" || !m.HasPublicStub() {
+			return
+		}
+
+		syspropPublicStubs := syspropPublicStubs(mctx.Config())
+		syspropPublicStubsLock.Lock()
+		defer syspropPublicStubsLock.Unlock()
+
+		syspropPublicStubs[m.BaseModuleName()] = m.JavaPublicStubName()
+	}
+}