bypass arguments parsing when target type is a map

This allows for unparsed forwarding of graphql arguments, in the case something application specific has to be done with the arguments.

Author: koenpunt

spring-graphql/src/main/java/org/springframework/graphql/data/method/annotation/support/ArgumentMethodArgumentResolver.java

@@ -74,10 +74,19 @@ public Object resolveArgument(MethodParameter parameter, DataFetchingEnvironment
 		if (CollectionFactory.isApproximableCollectionType(rawValue.getClass())) {
 			Assert.isAssignable(Collection.class, parameterType.getType(),
 					"Argument '" + name + "' is a Collection while the @Argument method parameter is " + parameterType.getType());
+
+			if (parameterType.getElementTypeDescriptor().getType() == Map.class) {
+				return rawValue;
+			}
+
 			Class<?> elementType = parameterType.getElementTypeDescriptor().getType();
 			return this.instantiator.instantiateCollection(elementType, (Collection<Object>) rawValue);
 		}
 
+		if (parameterType.isMap()) {
+			return rawValue;
+		}
+
 		MethodParameter nestedParameter = parameter.nestedIfOptional();
 		Object value = convert(rawValue, nestedParameter.getNestedParameterType());
 		return returnValue(value, parameterType.getType());

spring-graphql/src/test/java/org/springframework/graphql/data/method/annotation/support/ArgumentMethodArgumentResolverTests.java

@@ -18,6 +18,7 @@
 
 
 import java.lang.reflect.Method;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -98,6 +99,32 @@ void shouldResolveListOfJavaBeansArgument() throws Exception {
 				.extracting("name").containsExactly("first", "second");
 	}
 
+    @Test
+    void shouldPassArgumentAsMap() throws Exception {
+        Method updateBook = ClassUtils.getMethod(BookController.class, "updateBook", Long.class, Map.class);
+        String payload = "{\"id\": 43, \"input\": { \"name\": \"new name\", \"description\": null, \"authorId\": 42} }";
+        DataFetchingEnvironment environment = initEnvironment(payload);
+        MethodParameter methodParameter = getMethodParameter(updateBook, 1);
+        Object result = resolver.resolveArgument(methodParameter, environment);
+        assertThat(result).isNotNull().isInstanceOf(Map.class);
+        assertThat(result)
+                .hasFieldOrPropertyWithValue("name", "new name")
+                .hasFieldOrPropertyWithValue("description", null)
+                .hasFieldOrPropertyWithValue("authorId", 42);
+    }
+
+    @Test
+    void shouldPassArgumentAsList() throws Exception {
+        Method updateBook = ClassUtils.getMethod(BookController.class, "updateBooks", List.class);
+        String payload = "{\"input\": [{ \"id\": 1, \"name\": \"first\" }, { \"id\": 2, \"name\": \"second\" }] }";
+        DataFetchingEnvironment environment = initEnvironment(payload);
+        MethodParameter methodParameter = getMethodParameter(updateBook, 0);
+        Object result = resolver.resolveArgument(methodParameter, environment);
+        assertThat(result).isNotNull().isInstanceOf(List.class);
+        assertThat(result).asList().allMatch(item -> item instanceof Map)
+                .extracting("name").containsExactly("first", "second");
+    }
+
 	private MethodParameter getMethodParameter(Method method, int index) {
 		MethodParameter methodParameter = new MethodParameter(method, index);
 		methodParameter.initParameterNameDiscovery(new DefaultParameterNameDiscoverer());
@@ -132,6 +159,16 @@ public List<Book> addBooks(@Argument List<Book> books) {
 			return null;
 		}
 
+		@MutationMapping
+		public List<Book> updateBook(@Argument Long id, @Argument Map<String, ?> input) {
+			return null;
+		}
+
+        @MutationMapping
+        public List<Book> updateBooks(@Argument List<Map<String, ?>> input) {
+            return null;
+        }
+
 	}
 
 	static class BookInput {