Treat core_platform as stable unless module uses legacy

The sdk_version: "core_platform" refers to the stable core platform
unless the module is in the exception list. This change makes sure that
CheckStableSdkVersion() reflects that behavior.

Bug: 180399951
Test: m nothing
Change-Id: Ia0b1e13322352b87f5a3c6621e37f23ba637ffb6

apex/apex_test.go

@@ -1971,7 +1971,7 @@ func TestJavaStableSdkVersion(t *testing.T) {
 				java_library {
 					name: "myjar",
 					srcs: ["foo/bar/MyClass.java"],
-					sdk_version: "core_platform",
+					sdk_version: "test_current",
 					apex_available: ["myapex"],
 				}
 			`,
@@ -2018,13 +2018,16 @@ func TestJavaStableSdkVersion(t *testing.T) {
 				java_library {
 					name: "myjar",
 					srcs: ["foo/bar/MyClass.java"],
-					sdk_version: "core_platform",
+					sdk_version: "test_current",
 					apex_available: ["myapex"],
 				}
 			`,
 		},
 		{
-			name:          "Updatable apex with non-stable transitive dep",
+			name: "Updatable apex with non-stable transitive dep",
+			// This is not actually detecting that the transitive dependency is unstable, rather it is
+			// detecting that the transitive dependency is building against a wider API surface than the
+			// module that depends on it is using.
 			expectedError: "compiles against Android API, but dependency \"transitive-jar\" is compiling against private API.",
 			bp: `
 				apex {

java/java.go

@@ -122,7 +122,16 @@ func (j *Module) CheckStableSdkVersion() error {
 	if sdkVersion.stable() {
 		return nil
 	}
-	return fmt.Errorf("non stable SDK %v", sdkVersion)
+	if sdkVersion.kind == sdkCorePlatform {
+		if useLegacyCorePlatformApiByName(j.BaseModuleName()) {
+			return fmt.Errorf("non stable SDK %v - uses legacy core platform", sdkVersion)
+		} else {
+			// Treat stable core platform as stable.
+			return nil
+		}
+	} else {
+		return fmt.Errorf("non stable SDK %v", sdkVersion)
+	}
 }
 
 func (j *Module) checkSdkVersions(ctx android.ModuleContext) {

java/legacy_core_platform_api_usage.go

@@ -160,7 +160,11 @@ func init() {
 }
 
 func useLegacyCorePlatformApi(ctx android.EarlyModuleContext) bool {
-	_, found := legacyCorePlatformApiLookup[ctx.ModuleName()]
+	return useLegacyCorePlatformApiByName(ctx.ModuleName())
+}
+
+func useLegacyCorePlatformApiByName(name string) bool {
+	_, found := legacyCorePlatformApiLookup[name]
 	return found
 }