[JCW] Throw error if user tries to override a Kotlin name-mangled method. (#534)

src/Java.Interop.Tools.Diagnostics/Java.Interop.Tools.Diagnostics/Diagnostic.cs

@@ -103,6 +103,7 @@ namespace Java.Interop.Tools.Diagnostics {
 	//					XA4210 "You need to add a reference to Mono.Android.Export.dll when you use ExportAttribute or ExportFieldAttribute."
 	//					XA4211  AndroidManifest.xml //uses-sdk/@android:targetSdkVersion '{0}' is less than $(TargetFrameworkVersion) '{1}'. Using API-{1} for ACW compilation.
 	//					XA4212  Type `{0}` implements `Android.Runtime.IJavaObject` but does not inherit `Java.Lang.Object` or `Java.Lang.Throwable`. This is not supported.
+	//					XA4213  Cannot override Kotlin-generated method '{0}' because it is not a valid Java method name. This method can only be overridden from Kotlin."
 	// XA5xxx	GCC and toolchain
 	//			XA32xx	.apk generation
 	//					XA4300  Unsupported $(AndroidSupportedAbis) value '{0}'; ignoring.

src/Java.Interop.Tools.JavaCallableWrappers/Java.Interop.Tools.JavaCallableWrappers/JavaCallableWrapperGenerator.cs

@@ -362,6 +362,10 @@ void AddMethod (MethodDefinition registeredMethod, MethodDefinition implementedM
 		{
 			if (registeredMethod != null)
 				foreach (RegisterAttribute attr in GetRegisterAttributes (registeredMethod)) {
+					// Check for Kotlin-mangled methods that cannot be overridden
+					if (attr.Name.Contains ("-impl") || (attr.Name.Length > 7 && attr.Name[attr.Name.Length - 8] == '-'))
+						Diagnostic.Error (4213, LookupSource (implementedMethod), $"Cannot override Kotlin-generated method '{attr.Name}' because it is not a valid Java method name. This method can only be overridden from Kotlin.");
+
 					var msig = new Signature (implementedMethod, attr);
 					if (!registeredMethod.IsConstructor && !methods.Any (m => m.Name == msig.Name && m.Params == msig.Params))
 						methods.Add (msig);

tests/Java.Interop.Tools.JavaCallableWrappers-Tests/Java.Interop.Tools.JavaCallableWrappers/JavaCallableWrapperGeneratorTests.cs

@@ -30,6 +30,28 @@ public void ConstructorExceptions ()
 			Assert.AreEqual (4200, e.Code);
 		}
 
+		[Test]
+		public void KotlinInvalidImplRegisterName ()
+		{
+			Action<string, object []> logger = (f, o) => { };
+
+			// Contains invalid [Register] name of "foo-impl"
+			var td = SupportDeclarations.GetTypeDefinition (typeof (KotlinInvalidImplRegisterName));
+			var e = Assert.Throws<XamarinAndroidException> (() => new JavaCallableWrapperGenerator (td, logger));
+			Assert.AreEqual (4213, e.Code);
+		}
+
+		[Test]
+		public void KotlinInvalidHashRegisterName ()
+		{
+			Action<string, object []> logger = (f, o) => { };
+
+			// Contains invalid [Register] name of "foo-f8k2a13"
+			var td = SupportDeclarations.GetTypeDefinition (typeof (KotlinInvalidHashRegisterName));
+			var e = Assert.Throws<XamarinAndroidException> (() => new JavaCallableWrapperGenerator (td, logger));
+			Assert.AreEqual (4213, e.Code);
+		}
+
 		[Test]
 		public void GenerateApplication (
 				[Values (null, "android.app.Application", "android.support.multidex.MultiDexApplication")] string applicationJavaClass

tests/Java.Interop.Tools.JavaCallableWrappers-Tests/Java.Interop.Tools.JavaCallableWrappers/SupportDeclarations.cs

@@ -227,6 +227,34 @@ public class OverrideNestedName : Java.Lang.Object
 		}
 	}
 
+	[Register ("Kotlin.InvalidRegisterName")]
+	class KotlinInvalidRegisterName : Java.Lang.Object
+	{
+		[Register ("foo-impl")]
+		public virtual void Foo ()
+		{
+		}
+
+		[Register ("foo-f8k2a13")]
+		public virtual void Bar ()
+		{
+		}
+	}
+
+	[Register ("Kotlin.InvalidRegisterNameSubclass")]
+	class KotlinInvalidImplRegisterName : KotlinInvalidRegisterName
+	{
+		[Register ("foo-impl")]
+		public override void Foo () => base.Foo ();
+	}
+
+	[Register ("Kotlin.InvalidRegisterNameSubclass")]
+	class KotlinInvalidHashRegisterName : KotlinInvalidRegisterName
+	{
+		[Register ("foo-f8k2a13")]
+		public override void Bar () => base.Foo ();
+	}
+
 	[Service (Name = "service.Name")]
 	class ServiceName : Java.Lang.Object
 	{