Allow binding raw map to Map<String,?>

Closes gh-554

Author: rstoyanchev

spring-graphql/src/main/java/org/springframework/graphql/data/GraphQlArgumentBinder.java

@@ -245,10 +245,9 @@ private Map<?, Object> bindMapToMap(
 			ArgumentsBindingResult bindingResult) {
 
 		ResolvableType valueType = targetType.asMap().getGeneric(1);
-		Class<?> valueClass = valueType.resolve();
-		if (valueClass == null) {
-			bindingResult.rejectArgumentValue(name, null, "unknownType", "Unknown Map value type");
-			return Collections.emptyMap(); // Keep going, to record more errors
+		Class<?> valueClass = valueType.resolve(Object.class);
+		if (valueClass == Object.class) {
+			return rawMap;
 		}
 
 		Map<String, Object> map = CollectionFactory.createMap(targetClass, rawMap.size());

spring-graphql/src/test/java/org/springframework/graphql/data/GraphQlArgumentBinderTests.java

@@ -318,7 +318,7 @@ void primaryConstructorBindingErrorWithNestedBeanList() {
 	}
 
 	@Test
-	void primaryConstructorWithMapArgument() throws Exception {
+	void primaryConstructorWithItemMapArgument() throws Exception {
 
 		Object result = bind(
 				"{\"map\":{\"item1\":{\"name\":\"Jason\",\"age\":\"21\"},\"item2\":{\"name\":\"James\",\"age\":\"22\"}}}",
@@ -336,6 +336,25 @@ void primaryConstructorWithMapArgument() throws Exception {
 		assertThat(item2.getAge()).isEqualTo(22);
 	}
 
+	@Test // gh-554
+	void primaryConstructorWithRawMapArgument() throws Exception {
+
+		Object result = bind(
+				"{\"map\":{\"item1\":{\"name\":\"Jason\",\"age\":\"21\"},\"item2\":{\"name\":\"James\",\"age\":\"22\"}}}",
+				ResolvableType.forClass(PrimaryConstructorRawMapBean.class));
+
+		assertThat(result).isNotNull().isInstanceOf(PrimaryConstructorRawMapBean.class);
+		Map<String, ?> map = ((PrimaryConstructorRawMapBean) result).getMap();
+
+		Map<String, Object> item1 = (Map<String, Object>) map.get("item1");
+		assertThat(item1).containsEntry("name", "Jason");
+		assertThat(item1).containsEntry("age", "21");
+
+		Map<String, Object> item2 = (Map<String, Object>) map.get("item2");
+		assertThat(item2).containsEntry("name", "James");
+		assertThat(item2).containsEntry("age", "22");
+	}
+
 	@Test // gh-447
 	@SuppressWarnings("unchecked")
 	void primaryConstructorWithGenericObject() throws Exception {
@@ -476,6 +495,20 @@ public Map<String, Item> getMap() {
 	}
 
 
+	static class PrimaryConstructorRawMapBean {
+
+		private final Map<String, ?> map;
+
+		public PrimaryConstructorRawMapBean(Map<String, ?> map) {
+			this.map = map;
+		}
+
+		public Map<String, ?> getMap() {
+			return this.map;
+		}
+	}
+
+
 	@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
 	static class PrimaryConstructorOptionalItemBean {