Add support for args for DataFetcher declared in method

src/main/java/graphql/annotations/GraphQLAnnotations.java

@@ -188,7 +188,6 @@ public GraphQLInterfaceType.Builder getIfaceBuilder(Class<?> iface) throws Graph
         return builder;
     }
 
-
     public static GraphQLInterfaceType.Builder ifaceBuilder(Class<?> iface) throws GraphQLAnnotationsException,
             IllegalAccessException {
         return getInstance().getIfaceBuilder(iface);
@@ -410,22 +409,7 @@ protected GraphQLFieldDefinition getField(Field field) throws GraphQLAnnotations
         GraphQLDataFetcher dataFetcher = field.getAnnotation(GraphQLDataFetcher.class);
         DataFetcher actualDataFetcher = null;
         if (nonNull(dataFetcher)) {
-            final String[] args;
-            if (dataFetcher.firstArgIsTargetName()) {
-                args = Stream.concat(Stream.of(field.getName()), stream(dataFetcher.args())).toArray(String[]::new);
-            } else {
-                args = dataFetcher.args();
-            }
-            if (args.length == 0) {
-                actualDataFetcher = newInstance(dataFetcher.value());
-            } else {
-                try {
-                    final Constructor<? extends DataFetcher> ctr = dataFetcher.value().getDeclaredConstructor(
-                            stream(args).map(v -> String.class).toArray(Class[]::new));
-                    actualDataFetcher = constructNewInstance(ctr, (Object[]) args);
-                } catch (final NoSuchMethodException e) {
-                }
-            }
+            actualDataFetcher = constructDataFetcher(field.getName(), dataFetcher);
         }
 
         if (actualDataFetcher == null) {
@@ -469,6 +453,26 @@ protected GraphQLFieldDefinition getField(Field field) throws GraphQLAnnotations
         return new GraphQLFieldDefinitionWrapper(builder.build());
     }
 
+    private DataFetcher constructDataFetcher(String fieldName, GraphQLDataFetcher annotatedDataFetcher) {
+        final String[] args;
+        if ( annotatedDataFetcher.firstArgIsTargetName() ) {
+            args = Stream.concat(Stream.of(fieldName), stream(annotatedDataFetcher.args())).toArray(String[]::new);
+        } else {
+            args = annotatedDataFetcher.args();
+        }
+        if (args.length == 0) {
+            return newInstance(annotatedDataFetcher.value());
+        } else {
+            try {
+                final Constructor<? extends DataFetcher> ctr = annotatedDataFetcher.value().getDeclaredConstructor(
+                        stream(args).map(v -> String.class).toArray(Class[]::new));
+                return constructNewInstance(ctr, (Object[]) args);
+            } catch (final NoSuchMethodException e) {
+                throw new GraphQLAnnotationsException("Unable to instantiate DataFetcher via constructor for: " + fieldName, e);
+            }
+        }
+    }
+
     protected GraphQLFieldDefinition field(Field field) throws IllegalAccessException, InstantiationException {
         return getInstance().getField(field);
     }
@@ -592,7 +596,7 @@ protected GraphQLFieldDefinition getField(Method method) throws GraphQLAnnotatio
         } else if (dataFetcher == null) {
             actualDataFetcher = new MethodDataFetcher(method, typeFunction);
         } else {
-            actualDataFetcher = newInstance(dataFetcher.value());
+            actualDataFetcher = constructDataFetcher(method.getName(), dataFetcher);
         }
 
         if (method.isAnnotationPresent(GraphQLRelayMutation.class) && relay != null) {

src/test/java/graphql/annotations/GraphQLDataFetcherTest.java

@@ -26,6 +26,7 @@
 import java.util.HashMap;
 
 import static graphql.schema.GraphQLSchema.newSchema;
+import static org.testng.Assert.assertFalse;
 import static org.testng.Assert.assertNotNull;
 import static org.testng.Assert.assertTrue;
 
@@ -48,15 +49,58 @@ public void shouldUsePreferredConstructor() {
         assertTrue(((HashMap<String, Boolean>) data.get("sample")).get("isBad"));
     }
 
+    @Test
+    public void shouldUseProvidedSoloArgumentForDataFetcherDeclaredInMethod() {
+        // Given
+        final GraphQLObjectType object = GraphQLAnnotations.object(TestMethodWithDataFetcherGraphQLQuery.class);
+        final GraphQLSchema schema = newSchema().query(object).build();
+        final GraphQL graphql = GraphQL.newGraphQL(schema).build();
+
+        // When
+        final ExecutionResult result = graphql.execute("{great}");
+
+        // Then
+        final HashMap<String, Object> data = (HashMap) result.getData();
+        assertNotNull(data);
+        assertFalse((Boolean)data.get("great"));
+    }
+
+    @Test
+    public void shouldUseTargetAndArgumentsForDataFetcherDeclaredInMethod() {
+        // Given
+        final GraphQLObjectType object = GraphQLAnnotations.object(TestMethodWithDataFetcherGraphQLQuery.class);
+        final GraphQLSchema schema = newSchema().query(object).build();
+        final GraphQL graphql = GraphQL.newGraphQL(schema).build();
+
+        // When
+        final ExecutionResult result = graphql.execute("{sample {bad}}");
+
+        // Then
+        final HashMap<String, Object> data = (HashMap) result.getData();
+        assertNotNull(data);
+        assertTrue(((HashMap<String,Boolean>)data.get("sample")).get("bad"));
+    }
+
     @GraphQLName("Query")
     public static class TestGraphQLQuery {
         @GraphQLField
         @GraphQLDataFetcher(SampleDataFetcher.class)
         public TestSample sample() { // Note that GraphQL uses TestSample to build the graph
-            return null;
+          return null;
         }
     }
 
+    @GraphQLName("Query")
+    public static class TestMethodWithDataFetcherGraphQLQuery {
+        @GraphQLField
+        @GraphQLDataFetcher(value = SampleOneArgDataFetcher.class, args = "true")
+        public Boolean great() { return false; }
+
+        @GraphQLField
+        @GraphQLDataFetcher(SampleDataFetcher.class)
+        public TestSampleMethod sample() { return null; }
+    }
+
     public static class TestSample {
         @GraphQLField
         @GraphQLDataFetcher(value = PropertyDataFetcher.class, args = "isGreat")
@@ -68,13 +112,38 @@ public static class TestSample {
 
     }
 
+    public static class TestSampleMethod {
+
+        @GraphQLField
+        @GraphQLDataFetcher(value = SampleMultiArgDataFetcher.class, firstArgIsTargetName = true, args = {"true"})
+        public Boolean isBad() { return false; } // Defaults to FieldDataFetcher
+
+    }
+
     public static class SampleDataFetcher implements DataFetcher {
         @Override
         public Object get(final DataFetchingEnvironment environment) {
             return new Sample(); // Notice that it return a Sample, not a TestSample
         }
     }
 
+    public static class SampleOneArgDataFetcher implements DataFetcher {
+        private boolean flip = false;
+
+        public SampleOneArgDataFetcher(String flip) {
+          this.flip = Boolean.valueOf(flip);
+        }
+
+        @Override
+        public Object get(DataFetchingEnvironment environment) {
+            if ( flip ) {
+                return !flip;
+            } else {
+                return flip;
+            }
+        }
+    }
+
     public static class SampleMultiArgDataFetcher extends PropertyDataFetcher {
         private boolean flip = false;
 
@@ -87,7 +156,7 @@ public SampleMultiArgDataFetcher(String target, String flip) {
         public Object get(DataFetchingEnvironment environment) {
             final Object result = super.get(environment);
             if (flip) {
-                return !(Boolean) result;
+                return !(Boolean)result;
             } else {
                 return result;
             }