[generator] Handle Kotlin metadata when only one metadata exists for multiple Java methods.

src/Xamarin.Android.Tools.Bytecode/Kotlin/KotlinFixups.cs

@@ -47,11 +47,13 @@ public static void Fixup (IList<ClassFile> classes)
 					FixupJavaMethods (c.Methods);
 
 					if (metadata.Functions != null) {
-						foreach (var met in metadata.Functions)
-							FixupFunction (FindJavaMethod (metadata, met, c), met, class_metadata);
+						// We work from Java methods to Kotlin metadata because they aren't a 1:1 relation
+						// and we need to find the "best" match for each Java method.
+						foreach (var java_method in c.Methods)
+							if (FindKotlinFunctionMetadata (metadata, java_method) is KotlinFunction function_metadata)
+								FixupFunction (java_method, function_metadata, class_metadata);
 					}
 
-
 					if (metadata.Properties != null) {
 						foreach (var prop in metadata.Properties) {
 							var getter = FindJavaPropertyGetter (metadata, prop, c);
@@ -334,40 +336,40 @@ static void FixupField (FieldInfo? field, KotlinProperty metadata)
 			return null;
 		}
 
-		static MethodInfo? FindJavaMethod (KotlinFile kotlinFile, KotlinFunction function, ClassFile klass)
+		static KotlinFunction? FindKotlinFunctionMetadata (KotlinFile? kotlinFile, MethodInfo javaMethod)
 		{
-			var possible_methods = klass.Methods.Where (method => method.Name == function.JvmName).ToArray ();
-			var signature = function.JvmSignature;
+			if (kotlinFile?.Functions is null)
+				return null;
+
+			var java_descriptor = javaMethod.Descriptor;
 
-			// If the Descriptor/Signature match, that means all parameters and return type match
-			if (signature != null && possible_methods.SingleOrDefault (method => method.Descriptor == signature) is MethodInfo m)
-					return m;
+			// The method name absolutely has to match
+			var possible_functions = kotlinFile.Functions.Where (f => f.JvmName == javaMethod.Name).ToArray ();
+
+			// If we have metadata with a Descriptor/JvmSignature match, that means all parameters and return type match
+			if (possible_functions.SingleOrDefault (f => f.JvmSignature != null && f.JvmSignature == java_descriptor) is KotlinFunction kf)
+				return kf;
 
 			// Sometimes JvmSignature is null (or unhelpful), so we're going to construct one ourselves and see if they match
-			signature = function.ConstructJvmSignature ();
+			if (possible_functions.SingleOrDefault (f => f.ConstructJvmSignature () == java_descriptor) is KotlinFunction kf2)
+				return kf2;
 
-			if (possible_methods.SingleOrDefault (method => method.Descriptor == signature) is MethodInfo m2)
-				return m2;
+			// If that didn't work, let's try it the hard way!
+			// This catches cases where Kotlin only wrote one metadata entry for multiple methods with the same mangled JvmName (ex: contains-WZ4Q5Ns)
+			var java_param_count = javaMethod.GetFilteredParameters ().Length;
 
-			// If that didn't work, let's do it the hard way!
-			// I don't know if this catches anything additional, but it was the original code we shipped, so
-			// we'll keep it just in case something in the wild requires it.
-			foreach (var method in possible_methods.Where (method => method.GetFilteredParameters ().Length == function.ValueParameters?.Count)) {
+			foreach (var function in possible_functions.Where (f => f.ValueParameters?.Count == java_param_count)) {
 				if (function.ReturnType == null)
 					continue;
-				if (!TypesMatch (method.ReturnType, function.ReturnType, kotlinFile))
+				if (!TypesMatch (javaMethod.ReturnType, function.ReturnType, kotlinFile))
 					continue;
 
-				if (!ParametersMatch (kotlinFile, method, function.ValueParameters!))
+				if (!ParametersMatch (kotlinFile, javaMethod, function.ValueParameters!))
 					continue;
 
-				return method;
+				return function;
 			}
 
-			// Theoretically this should never be hit, but who knows. At worst, it just means
-			// Kotlin niceties won't be applied to the method.
-			Log.Debug ($"Kotlin: Could not find Java method to match '{function.Name} ({function.ConstructJvmSignature ()})'");
-
 			return null;
 		}
 

tests/Xamarin.Android.Tools.Bytecode-Tests/KotlinFixupsTests.cs

@@ -374,5 +374,27 @@ public void MatchParametersWithStaticThis ()
 			Assert.AreEqual (1, start);
 			Assert.AreEqual (2, end);
 		}
+
+		[Test]
+		public void MatchMetadataToMultipleMethodsWithSameMangledName ()
+		{
+			var klass = LoadClassFile ("UByteArray.class");
+			var meta = GetClassMetadataForClass (klass);
+
+			// There is only one Kotlin metadata for Java method "contains-7apg3OU"
+			var kotlin_function = meta.Functions.Single (m => m.Name == "contains");
+
+			// However there are 2 Java methods named "contains-7apg3OU"
+			// - public boolean contains-7apg3OU (byte element)
+			// - public static boolean contains-7apg3OU (byte[] arg0, byte element)
+			var java_methods = klass.Methods.Where (m => m.Name == "contains-7apg3OU");
+			Assert.AreEqual (2, java_methods.Count ());
+
+			KotlinFixups.Fixup (new [] { klass });
+
+			// Ensure the fixup "fixed" the parameter "element" type to "ubyte"
+			Assert.AreEqual ("ubyte", java_methods.ElementAt (0).GetParameters ().Single (p => p.Name == "element").KotlinType);
+			Assert.AreEqual ("ubyte", java_methods.ElementAt (1).GetParameters ().Single (p => p.Name == "element").KotlinType);
+		}
 	}
 }