Improve "Connection" schema type checks

ConnectionFieldTypeVisitor now checks the complete structure
of Connection, Edge, and PageInfo schema types before
decorating a DataFetcher.

See gh-709

spring-graphql/src/main/java/org/springframework/graphql/data/pagination/ConnectionFieldTypeVisitor.java

@@ -34,8 +34,10 @@ import graphql.schema.DataFetchingEnvironment;
 import graphql.schema.GraphQLCodeRegistry;
 import graphql.schema.GraphQLFieldDefinition;
 import graphql.schema.GraphQLFieldsContainer;
+import graphql.schema.GraphQLList;
 import graphql.schema.GraphQLNonNull;
 import graphql.schema.GraphQLObjectType;
+import graphql.schema.GraphQLOutputType;
 import graphql.schema.GraphQLSchemaElement;
 import graphql.schema.GraphQLType;
 import graphql.schema.GraphQLTypeVisitorStub;
@@ -101,14 +103,54 @@ public final class ConnectionFieldTypeVisitor extends GraphQLTypeVisitorStub {
 		return TraversalControl.CONTINUE;
 	}
 
-	private static boolean isConnectionField(GraphQLFieldDefinition fieldDefinition) {
-		GraphQLType returnType = fieldDefinition.getType();
-		if (returnType instanceof GraphQLNonNull nonNullType) {
-			returnType = nonNullType.getWrappedType();
+	private static boolean isConnectionField(GraphQLFieldDefinition field) {
+		GraphQLObjectType type = getAsObjectType(field);
+		if (type == null || !type.getName().endsWith("Connection")) {
+			return false;
 		}
-		return (returnType instanceof GraphQLObjectType objectType &&
-				objectType.getName().endsWith("Connection") &&
-				objectType.getField("pageInfo") != null);
+
+		GraphQLObjectType edgeType = getEdgeType(type.getField("edges"));
+		if (edgeType == null || !edgeType.getName().endsWith("Edge")) {
+			return false;
+		}
+		if (edgeType.getField("node") == null || edgeType.getField("cursor") == null) {
+			return false;
+		}
+
+		GraphQLObjectType pageInfoType = getAsObjectType(type.getField("pageInfo"));
+		if (pageInfoType == null || !pageInfoType.getName().equals("PageInfo")) {
+			return false;
+		}
+		if (pageInfoType.getField("hasPreviousPage") == null || pageInfoType.getField("hasNextPage") == null ||
+				pageInfoType.getField("startCursor") == null || pageInfoType.getField("endCursor") == null) {
+			return false;
+		}
+
+		return true;
+	}
+
+	@Nullable
+	private static GraphQLObjectType getAsObjectType(@Nullable GraphQLFieldDefinition field) {
+		return (getType(field) instanceof GraphQLObjectType type ? type : null);
+	}
+
+	@Nullable
+	private static GraphQLObjectType getEdgeType(@Nullable GraphQLFieldDefinition field) {
+		if (getType(field) instanceof GraphQLList listType) {
+			if (listType.getWrappedType() instanceof GraphQLObjectType type) {
+				return type;
+			}
+		}
+		return null;
+	}
+
+	@Nullable
+	private static GraphQLType getType(@Nullable GraphQLFieldDefinition field) {
+		if (field == null) {
+			return null;
+		}
+		GraphQLOutputType type = field.getType();
+		return (type instanceof GraphQLNonNull nonNullType ? nonNullType.getWrappedType() : type);
 	}
 
 

spring-graphql/src/test/java/org/springframework/graphql/data/pagination/ConnectionFieldTypeVisitorTests.java

@@ -19,14 +19,28 @@ package org.springframework.graphql.data.pagination;
 import java.util.Collection;
 import java.util.List;
 
+import graphql.schema.DataFetcher;
+import graphql.schema.FieldCoordinates;
+import graphql.schema.GraphQLFieldDefinition;
+import graphql.schema.GraphQLSchema;
 import graphql.schema.PropertyDataFetcher;
+import graphql.schema.SchemaTransformer;
+import graphql.schema.idl.RuntimeWiring;
+import graphql.schema.idl.SchemaGenerator;
+import graphql.schema.idl.SchemaParser;
+import graphql.schema.idl.TypeDefinitionRegistry;
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 import reactor.core.publisher.Mono;
 
+import org.springframework.core.io.Resource;
 import org.springframework.graphql.BookSource;
 import org.springframework.graphql.ExecutionGraphQlResponse;
 import org.springframework.graphql.GraphQlSetup;
 import org.springframework.graphql.ResponseHelper;
+import org.springframework.graphql.execution.ConnectionTypeDefinitionConfigurer;
+
+import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Unit tests for {@link ConnectionFieldTypeVisitor}.
@@ -69,18 +83,6 @@ public class ConnectionFieldTypeVisitorTests {
 		);
 	}
 
-	@Test // gh-707
-	void trivialDataFetcherIsSkipped() {
-
-		Mono<ExecutionGraphQlResponse> response = GraphQlSetup.schemaResource(BookSource.paginationSchema)
-				.dataFetcher("Query", "books", new PropertyDataFetcher<>("books"))
-				.connectionSupport(new ListConnectionAdapter())
-				.toGraphQlService()
-				.execute(BookSource.booksConnectionQuery(null));
-
-		ResponseHelper.forResponse(response).assertData("{\"books\":null}");
-	}
-
 	@Test // gh-707
 	void nullValueTreatedAsEmptyConnection() {
 
@@ -103,6 +105,85 @@ public class ConnectionFieldTypeVisitorTests {
 	}
 
 
+	@Nested
+	class DecorationTests {
+
+		@Test // gh-707
+		void trivialDataFetcherIsNotDecorated() throws Exception {
+
+			FieldCoordinates coordinates = FieldCoordinates.coordinates("Query", "books");
+			DataFetcher<?> dataFetcher = new PropertyDataFetcher<>("books");
+
+			DataFetcher<?> actual =
+					applyConnectionFieldTypeVisitor(BookSource.paginationSchema, coordinates, dataFetcher);
+
+			assertThat(actual).isSameAs(dataFetcher);
+		}
+
+		@Test // gh-709
+		void connectionTypeWithoutEdgesIsNotDecorated() throws Exception {
+
+			String schemaContent = """
+				type Query {
+					puzzles: PuzzleConnection
+				}
+				type PuzzleConnection {
+					pageInfo: PuzzlePageInfo!
+					puzzles: [PuzzleEdge]
+				}
+				type PuzzlePageInfo {
+					total: Int!
+				}
+				type PuzzleEdge {
+					puzzle: Puzzle
+					cursor: String!
+				}
+				type Puzzle {
+					title: String!
+				}
+				""";
+
+			FieldCoordinates coordinates = FieldCoordinates.coordinates("Query", "puzzles");
+			DataFetcher<?> dataFetcher = env -> null;
+
+			DataFetcher<?> actual = applyConnectionFieldTypeVisitor(schemaContent, coordinates, dataFetcher);
+
+			assertThat(actual).isSameAs(dataFetcher);
+		}
+
+		private static DataFetcher<?> applyConnectionFieldTypeVisitor(
+				Object schemaSource, FieldCoordinates coordinates, DataFetcher<?> fetcher) throws Exception {
+
+			TypeDefinitionRegistry registry;
+			if (schemaSource instanceof Resource resource) {
+				registry = new SchemaParser().parse(resource.getInputStream());
+			}
+			else if (schemaSource instanceof String schemaContent) {
+				registry = new SchemaParser().parse(schemaContent);
+			}
+			else {
+				throw new IllegalArgumentException();
+			}
+
+			new ConnectionTypeDefinitionConfigurer().configure(registry);
+
+			GraphQLSchema schema = new SchemaGenerator().makeExecutableSchema(
+					registry, RuntimeWiring.newRuntimeWiring()
+							.type(coordinates.getTypeName(), b -> b.dataFetcher(coordinates.getFieldName(), fetcher))
+							.build());
+
+			ConnectionFieldTypeVisitor visitor =
+					ConnectionFieldTypeVisitor.create(List.of(new ListConnectionAdapter()));
+
+			schema = new SchemaTransformer().transform(schema, visitor);
+			GraphQLFieldDefinition field = schema.getFieldDefinition(coordinates);
+			return schema.getCodeRegistry().getDataFetcher(coordinates, field);
+		}
+
+	}
+
+
+
 	private static class ListConnectionAdapter implements ConnectionAdapter {
 
 		private int initialOffset = 0;