Correctly report skipped concrete union/interface types

Closes gh-962

Author: rstoyanchev

spring-graphql/src/main/java/org/springframework/graphql/execution/SchemaMappingInspector.java

@@ -220,14 +220,15 @@ else if (typePair.outputType() instanceof GraphQLInterfaceType interfaceType) {
 				// Can we inspect GraphQL type?
 				if (!(graphQlType instanceof GraphQLFieldsContainer fieldContainer)) {
 					if (isNotScalarOrEnumType(graphQlType)) {
-						this.reportBuilder.skippedType(graphQlType, parent, field, "Unsupported schema type");
+						this.reportBuilder.skippedType(graphQlType, parent, field, "Unsupported schema type", false);
 					}
 					continue;
 				}
 
 				// Can we inspect the Class?
 				if (currentResolvableType.resolve(Object.class) == Object.class) {
-					this.reportBuilder.skippedType(graphQlType, parent, field, "No class information");
+					boolean isDerived = !graphQlType.equals(typePair.outputType());
+					this.reportBuilder.skippedType(graphQlType, parent, field, "No class information", isDerived);
 					continue;
 				}
 
@@ -723,7 +724,9 @@ private final class ReportBuilder {
 
 		private final MultiValueMap<DataFetcher<?>, String> unmappedArguments = new LinkedMultiValueMap<>();
 
-		private final List<SchemaReport.SkippedType> skippedTypes = new ArrayList<>();
+		private final List<DefaultSkippedType> skippedTypes = new ArrayList<>();
+
+		private final List<DefaultSkippedType> candidateSkippedTypes = new ArrayList<>();
 
 		void unmappedField(FieldCoordinates coordinates) {
 			this.unmappedFields.add(coordinates);
@@ -737,19 +740,44 @@ void unmappedArgument(DataFetcher<?> dataFetcher, List<String> arguments) {
 			this.unmappedArguments.put(dataFetcher, arguments);
 		}
 
-		void skippedType(GraphQLType type, GraphQLFieldsContainer parent, GraphQLFieldDefinition field, String reason) {
-			DefaultSkippedType skippedType = DefaultSkippedType.create(type, parent, field);
+		void skippedType(
+				GraphQLType type, GraphQLFieldsContainer parent, GraphQLFieldDefinition field,
+				String reason, boolean isDerivedType) {
+
+			DefaultSkippedType skippedType = DefaultSkippedType.create(type, parent, field, reason);
+
+			if (!isDerivedType) {
+				skippedType(skippedType);
+				return;
+			}
+
+			// Keep skipped union member or interface implementing types aside to the end.
+			// Use of concrete types elsewhere may provide more information.
+
+			this.candidateSkippedTypes.add(skippedType);
+		}
+
+		private void skippedType(DefaultSkippedType skippedType) {
 			if (logger.isDebugEnabled()) {
-				logger.debug("Skipping '" + skippedType + "': " + reason);
+				logger.debug("Skipping '" + skippedType + "': " + skippedType.reason());
 			}
 			this.skippedTypes.add(skippedType);
 		}
 
 		SchemaReport build() {
+
+			this.candidateSkippedTypes.forEach((skippedType) -> {
+				if (skippedType.type() instanceof GraphQLFieldsContainer fieldsContainer) {
+					if (SchemaMappingInspector.this.inspectedTypes.contains(fieldsContainer.getName())) {
+						return;
+					}
+				}
+				skippedType(skippedType);
+			});
+
 			return new DefaultSchemaReport(
 					this.unmappedFields, this.unmappedRegistrations, this.unmappedArguments, this.skippedTypes);
 		}
-
 	}
 
 
@@ -768,7 +796,7 @@ private final class DefaultSchemaReport implements SchemaReport {
 
 		DefaultSchemaReport(
 				List<FieldCoordinates> unmappedFields, Map<FieldCoordinates, DataFetcher<?>> unmappedRegistrations,
-				MultiValueMap<DataFetcher<?>, String> unmappedArguments, List<SkippedType> skippedTypes) {
+				MultiValueMap<DataFetcher<?>, String> unmappedArguments, List<DefaultSkippedType> skippedTypes) {
 
 			this.unmappedFields = Collections.unmodifiableList(unmappedFields);
 			this.unmappedRegistrations = Collections.unmodifiableMap(unmappedRegistrations);
@@ -834,17 +862,18 @@ private String formatUnmappedFields() {
 	 * Default implementation of a {@link SchemaReport.SkippedType}.
 	 */
 	private record DefaultSkippedType(
-			GraphQLType type, FieldCoordinates fieldCoordinates) implements SchemaReport.SkippedType {
+			GraphQLType type, FieldCoordinates fieldCoordinates, String reason)
+			implements SchemaReport.SkippedType {
 
 		@Override
 		public String toString() {
-			return (type instanceof GraphQLNamedType namedType) ? namedType.getName() : type.toString();
+			return (this.type instanceof GraphQLNamedType named) ? named.getName() : this.type.toString();
 		}
 
 		public static DefaultSkippedType create(
-				GraphQLType type, GraphQLFieldsContainer parent, GraphQLFieldDefinition field) {
+				GraphQLType type, GraphQLFieldsContainer parent, GraphQLFieldDefinition field, String reason) {
 
-			return new DefaultSkippedType(type, FieldCoordinates.coordinates(parent, field));
+			return new DefaultSkippedType(type, FieldCoordinates.coordinates(parent, field), reason);
 		}
 	}
 

spring-graphql/src/test/java/org/springframework/graphql/execution/SchemaMappingInspectorUnionTests.java

@@ -22,6 +22,7 @@
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.graphql.data.method.annotation.Argument;
 import org.springframework.graphql.data.method.annotation.QueryMapping;
 import org.springframework.graphql.execution.SchemaMappingInspector.ClassResolver;
 import org.springframework.stereotype.Controller;
@@ -35,16 +36,20 @@ public class SchemaMappingInspectorUnionTests extends SchemaMappingInspectorTest
 
 	private static final String schema = """
 				type Query {
-					search: [SearchResult!]!
+					search: [SearchResult]
+					article(id: ID): Article
 				}
-				union SearchResult = Photo | Video
+				union SearchResult = Article | Photo | Video
 				type Photo {
 					height: Int
 					width: Int
 				}
 				type Video {
 					title: String
 				}
+				type Article {
+					content: String
+				}
 				""";
 
 
@@ -55,8 +60,10 @@ class UnmappedFields {
 		void reportUnmappedFieldsByCheckingReturnTypePackage() {
 			SchemaReport report = inspectSchema(schema, SearchController.class);
 			assertThatReport(report)
-					.hasSkippedTypeCount(0)
-					.hasUnmappedFieldCount(3)
+					.hasSkippedTypeCount(1)
+					.containsSkippedTypes("Article")
+					.hasUnmappedFieldCount(4)
+					.containsUnmappedFields("Query", "article")
 					.containsUnmappedFields("Photo", "height", "width")
 					.containsUnmappedFields("Video", "title");
 		}
@@ -65,17 +72,20 @@ void reportUnmappedFieldsByCheckingReturnTypePackage() {
 		void reportUnmappedFieldsByCheckingControllerTypePackage() {
 			SchemaReport report = inspectSchema(schema, ObjectSearchController.class);
 			assertThatReport(report)
-					.hasSkippedTypeCount(0)
-					.hasUnmappedFieldCount(3)
+					.hasSkippedTypeCount(1)
+					.containsSkippedTypes("Article")
+					.hasUnmappedFieldCount(4)
+					.containsUnmappedFields("Query", "article")
 					.containsUnmappedFields("Photo", "height", "width")
 					.containsUnmappedFields("Video", "title");
 		}
 
 
-		sealed interface ResultItem permits Photo, Video { }
 		record Photo() implements ResultItem { }
 		record Video() implements ResultItem { }
 
+		sealed interface ResultItem permits Photo, Video { }
+
 		@Controller
 		static class SearchController {
 
@@ -108,8 +118,10 @@ void classNameFunction() {
 					SearchController.class);
 
 			assertThatReport(report)
-					.hasSkippedTypeCount(0)
-					.hasUnmappedFieldCount(3)
+					.hasSkippedTypeCount(1)
+					.containsSkippedTypes("Article")
+					.hasUnmappedFieldCount(4)
+					.containsUnmappedFields("Query", "article")
 					.containsUnmappedFields("Photo", "height", "width")
 					.containsUnmappedFields("Video", "title");
 		}
@@ -124,8 +136,11 @@ void classNameTypeResolver() {
 					SearchController.class);
 
 			assertThatReport(report)
-					.hasUnmappedFieldCount(2).containsUnmappedFields("Photo", "height", "width")
-					.hasSkippedTypeCount(1).containsSkippedTypes("Video");
+					.hasSkippedTypeCount(2)
+					.containsSkippedTypes("Article", "Video")
+					.hasUnmappedFieldCount(3)
+					.containsUnmappedFields("Query", "article")
+					.containsUnmappedFields("Photo", "height", "width");
 		}
 
 		sealed interface ResultItem permits PhotoImpl, VideoImpl { }
@@ -149,7 +164,7 @@ class SkippedTypes {
 		@Test
 		void reportSkippedImplementations() {
 			SchemaReport report = inspectSchema(schema, SearchController.class);
-			assertThatReport(report).hasSkippedTypeCount(2).containsSkippedTypes("Photo", "Video");
+			assertThatReport(report).hasSkippedTypeCount(3).containsSkippedTypes("Article", "Photo", "Video");
 		}
 
 		interface ResultItem { }
@@ -164,4 +179,38 @@ List<ResultItem> search() {
 		}
 	}
 
+
+	@Nested
+	class CandidateSkippedTypes {
+
+		// A union member type is only a candidate to be skipped until the inspection is done.
+		// Use of the concrete type elsewhere may provide more information.
+
+		@Test
+		void candidateNotSkippedIfConcreteUseElsewhere() {
+			SchemaReport report = inspectSchema(schema, SearchController.class);
+			assertThatReport(report).hasSkippedTypeCount(2).containsSkippedTypes("Photo", "Video");
+		}
+
+		@Controller
+		static class SearchController {
+
+			@QueryMapping
+			List<Object> search() {
+				throw new UnsupportedOperationException();
+			}
+
+			@QueryMapping
+			Article article(@Argument Long id) {
+				throw new UnsupportedOperationException();
+			}
+		}
+	}
+
+
+	/**
+	 * Declared outside {@link CandidateSkippedTypes}, so the union lookup won't find it.
+	 */
+	private record Article(String content) { }
+
 }