Add hook for the inspection of schema mappings

Closes gh-672

Author: rstoyanchev

spring-graphql-docs/src/docs/asciidoc/index.adoc

@@ -417,18 +417,30 @@ implement this interface. That includes those for <<controllers>>, and those for
 controllers, the return type is derived from the declared return type on a
 `@SchemaMapping` method.
 
-On startup, Spring for GraphQL inspects all schema fields, `DataFetcher` registrations,
+On startup, Spring for GraphQL can inspect schema fields, `DataFetcher` registrations,
 and the properties of Java objects returned from `DataFetcher` implementations to check
 if all schema fields are covered either by an explicitly registered `DataFetcher`, or
 a matching Java object property. The inspection also performs a reverse check looking for
-`DataFetcher` registrations against schema fields that don't exist. This inspection is
-performed automatically, and results in a report that is logged at INFO level on startup.
-For example:
+`DataFetcher` registrations against schema fields that don't exist.
+
+To enable inspection of schema mappings:
+
+[source,java,indent=0,subs="verbatim,quotes"]
+----
+GraphQlSource.Builder builder = ...
+
+builder.schemaResources(..)
+		.inspectSchemaMappings(report -> {
+			logger.debug(report);
+		})
+----
+
+Below is an example report:
 
 ----
 GraphQL schema inspection:
     Unmapped fields: {Book=[title], Author[firstName, lastName]} // <1>
-    Unmapped DataFetcher registrations: {Book.reviews=BookController#reviews[1 args]} <2>
+    Unmapped registrations: {Book.reviews=BookController#reviews[1 args]} <2>
     Skipped types: [BookOrAuthor] // <3>
 ----
 

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

@@ -24,6 +24,7 @@
 import java.util.List;
 import java.util.Set;
 import java.util.function.BiFunction;
+import java.util.function.Consumer;
 import java.util.stream.Collectors;
 
 import graphql.language.InterfaceTypeDefinition;
@@ -71,6 +72,9 @@ final class DefaultSchemaResourceGraphQlSourceBuilder
 	@Nullable
 	private BiFunction<TypeDefinitionRegistry, RuntimeWiring, GraphQLSchema> schemaFactory;
 
+	@Nullable
+	private Consumer<SchemaReport> schemaReportConsumer;
+
 
 	@Override
 	public DefaultSchemaResourceGraphQlSourceBuilder schemaResources(Resource... resources) {
@@ -96,6 +100,12 @@ public DefaultSchemaResourceGraphQlSourceBuilder defaultTypeResolver(TypeResolve
 		return this;
 	}
 
+	@Override
+	public GraphQlSource.SchemaResourceBuilder inspectSchemaMappings(Consumer<SchemaReport> consumer) {
+		this.schemaReportConsumer = consumer;
+		return this;
+	}
+
 	@Override
 	public DefaultSchemaResourceGraphQlSourceBuilder schemaFactory(
 			BiFunction<TypeDefinitionRegistry, RuntimeWiring, GraphQLSchema> schemaFactory) {
@@ -136,11 +146,13 @@ protected GraphQLSchema initGraphQlSchema() {
 		// SchemaMappingInspector needs RuntimeWiring, but cannot run here since type
 		// visitors may transform the schema, for example to add Connection types.
 
-		configureGraphQl(builder -> {
-			GraphQLSchema schema = builder.build().getGraphQLSchema();
-			SchemaReport report = SchemaMappingInspector.inspect(schema, runtimeWiring);
-			logger.info(report);
-		});
+		if (this.schemaReportConsumer != null) {
+			configureGraphQl(builder -> {
+				GraphQLSchema schema = builder.build().getGraphQLSchema();
+				SchemaReport report = SchemaMappingInspector.inspect(schema, runtimeWiring);
+				this.schemaReportConsumer.accept(report);
+			});
+		}
 
 		return (this.schemaFactory != null ?
 				this.schemaFactory.apply(registry, runtimeWiring) :

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

@@ -19,7 +19,6 @@
 import java.util.List;
 import java.util.function.BiFunction;
 import java.util.function.Consumer;
-import java.util.function.Function;
 
 import graphql.GraphQL;
 import graphql.execution.instrumentation.Instrumentation;
@@ -201,6 +200,16 @@ interface SchemaResourceBuilder extends Builder<SchemaResourceBuilder> {
 		 */
 		SchemaResourceBuilder defaultTypeResolver(TypeResolver typeResolver);
 
+		/**
+		 * Enable inspection of schema mappings to find unmapped fields and
+		 * unmapped {@code DataFetcher} registrations. For more details, see
+		 * {@link SchemaReport} and the reference documentation.
+		 * @param reportConsumer a hook to inspect the report
+		 * @return the current builder
+		 * @since 1.2.0
+		 */
+		SchemaResourceBuilder inspectSchemaMappings(Consumer<SchemaReport> reportConsumer);
+
 		/**
 		 * Configure a function to create the {@link GraphQLSchema} from the
 		 * given {@link TypeDefinitionRegistry} and {@link RuntimeWiring}.