Add a rule about platform_apis

As sdk_check.mk checks, soong starts to check every app.
If sdk_version is empty, platform_apis must be true.
If sdk_version is not empty, platform_apis must be false.

Test: soong test
Test: m
Bug: 132780927
Change-Id: I7ba702d616404d155f8ac40cd008828663ad1488

java/java.go

@@ -52,6 +52,20 @@ func init() {
 	android.RegisterSingletonType("logtags", LogtagsSingleton)
 }
 
+func (j *Module) checkPlatformAPI(ctx android.ModuleContext) {
+	if sc, ok := ctx.Module().(sdkContext); ok {
+		usePlatformAPI := proptools.Bool(j.deviceProperties.Platform_apis)
+		if usePlatformAPI != (sc.sdkVersion() == "") {
+			if usePlatformAPI {
+				ctx.PropertyErrorf("platform_apis", "platform_apis must be false when sdk_version is not empty.")
+			} else {
+				ctx.PropertyErrorf("platform_apis", "platform_apis must be true when sdk_version is empty.")
+			}
+		}
+
+	}
+}
+
 // TODO:
 // Autogenerated files:
 //  Renderscript
@@ -178,8 +192,8 @@ type CompilerDeviceProperties struct {
 	// list of module-specific flags that will be used for dex compiles
 	Dxflags []string `android:"arch_variant"`
 
-	// if not blank, set to the version of the sdk to compile against.  Defaults to compiling against the current
-	// sdk if platform_apis is not set.
+	// if not blank, set to the version of the sdk to compile against.
+	// Defaults to compiling against the current platform.
 	Sdk_version *string
 
 	// if not blank, set the minimum version of the sdk that the compiled artifacts will run against.
@@ -190,7 +204,8 @@ type CompilerDeviceProperties struct {
 	// Defaults to sdk_version if not set.
 	Target_sdk_version *string
 
-	// if true, compile against the platform APIs instead of an SDK.
+	// It must be true only if sdk_version is empty.
+	// This field works in only android_app, otherwise nothing happens.
 	Platform_apis *bool
 
 	Aidl struct {