Refine GraphQL server auto-configuration

Prior to this commit, launching a GraphQL application without any schema
file or customizer bean would result in an exception caught by a
FailureAnalyzer telling the developer about configured locations.

Since then, a new client has been introduced in Spring GraphQL and the
mere presence of the GraphQL starter does not mean anymore that the
intent is to create a GraphQL API in the app: we could instead just
consume an existing, remote API.

This commit refines the GraphQL server auto-configuration so that it is
enabled only if:

* there is at least one schema file in the configured locations
* or a `GraphQlSourceCustomizer` bean has been defined in the app

These changes make the custom FailureAnalyzer useless and is also
removed as part of this commit.

Closes gh-30035

Author: bclozel

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/ConditionalOnGraphQlSchema.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.graphql;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.context.annotation.Conditional;
+
+/**
+ * {@link Conditional @Conditional} that only matches when a GraphQL schema is defined for
+ * the application, via schema files or infrastructure beans.
+ *
+ * @author Brian Clozel
+ * @since 2.7.0
+ */
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Conditional(DefaultGraphQlSchemaCondition.class)
+public @interface ConditionalOnGraphQlSchema {
+
+}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/DefaultGraphQlSchemaCondition.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright 2012-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.graphql;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.boot.autoconfigure.condition.ConditionMessage;
+import org.springframework.boot.autoconfigure.condition.ConditionOutcome;
+import org.springframework.boot.autoconfigure.condition.SpringBootCondition;
+import org.springframework.boot.context.properties.bind.Binder;
+import org.springframework.context.annotation.Condition;
+import org.springframework.context.annotation.ConditionContext;
+import org.springframework.context.annotation.ConfigurationCondition;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.support.ResourcePatternResolver;
+import org.springframework.core.io.support.ResourcePatternUtils;
+import org.springframework.core.type.AnnotatedTypeMetadata;
+
+/**
+ * {@link Condition} that checks whether a GraphQL schema has been defined in the
+ * application. This is looking for:
+ * <ul>
+ * <li>schema files in the {@link GraphQlProperties configured locations}</li>
+ * <li>or infrastructure beans such as {@link GraphQlSourceBuilderCustomizer}</li>
+ * </ul>
+ *
+ * @author Brian Clozel
+ * @see ConditionalOnGraphQlSchema
+ */
+class DefaultGraphQlSchemaCondition extends SpringBootCondition implements ConfigurationCondition {
+
+	@Override
+	public ConfigurationCondition.ConfigurationPhase getConfigurationPhase() {
+		return ConfigurationCondition.ConfigurationPhase.REGISTER_BEAN;
+	}
+
+	@Override
+	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
+		boolean match = false;
+		List<ConditionMessage> messages = new ArrayList<>(2);
+		ConditionMessage.Builder message = ConditionMessage.forCondition(ConditionalOnGraphQlSchema.class);
+
+		Binder binder = Binder.get(context.getEnvironment());
+		GraphQlProperties.Schema schema = binder.bind("spring.graphql.schema", GraphQlProperties.Schema.class)
+				.orElse(new GraphQlProperties.Schema());
+		ResourcePatternResolver resourcePatternResolver = ResourcePatternUtils
+				.getResourcePatternResolver(context.getResourceLoader());
+		List<Resource> schemaResources = resolveSchemaResources(resourcePatternResolver, schema.getLocations(),
+				schema.getFileExtensions());
+		if (!schemaResources.isEmpty()) {
+			match = true;
+			messages.add(message.found("schema", "schemas").items(ConditionMessage.Style.QUOTE, schemaResources));
+		}
+		else {
+			messages.add(message.didNotFind("schema files in locations").items(ConditionMessage.Style.QUOTE,
+					Arrays.asList(schema.getLocations())));
+		}
+		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
+		String[] customizerBeans = beanFactory.getBeanNamesForType(GraphQlSourceBuilderCustomizer.class, false, false);
+		if (customizerBeans.length != 0) {
+			match = true;
+			messages.add(message.found("customizer", "customizers").items(Arrays.asList(customizerBeans)));
+		}
+		else {
+			messages.add((message.didNotFind("GraphQlSourceBuilderCustomizer").atAll()));
+		}
+		return new ConditionOutcome(match, ConditionMessage.of(messages));
+	}
+
+	private List<Resource> resolveSchemaResources(ResourcePatternResolver resolver, String[] locations,
+			String[] extensions) {
+		List<Resource> resources = new ArrayList<>();
+		for (String location : locations) {
+			for (String extension : extensions) {
+				resources.addAll(resolveSchemaResources(resolver, location + "*" + extension));
+			}
+		}
+		return resources;
+	}
+
+	private List<Resource> resolveSchemaResources(ResourcePatternResolver resolver, String pattern) {
+		try {
+			return Arrays.asList(resolver.getResources(pattern));
+		}
+		catch (IOException ex) {
+			return Collections.emptyList();
+		}
+	}
+
+}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/GraphQlAutoConfiguration.java

@@ -48,7 +48,6 @@
 import org.springframework.graphql.execution.DefaultBatchLoaderRegistry;
 import org.springframework.graphql.execution.ExecutionGraphQlService;
 import org.springframework.graphql.execution.GraphQlSource;
-import org.springframework.graphql.execution.MissingSchemaException;
 import org.springframework.graphql.execution.RuntimeWiringConfigurer;
 
 /**
@@ -60,6 +59,7 @@
  */
 @AutoConfiguration
 @ConditionalOnClass({ GraphQL.class, GraphQlSource.class })
+@ConditionalOnGraphQlSchema
 @EnableConfigurationProperties(GraphQlProperties.class)
 public class GraphQlAutoConfiguration {
 
@@ -87,12 +87,7 @@ public GraphQlSource graphQlSource(ResourcePatternResolver resourcePatternResolv
 		}
 		wiringConfigurers.orderedStream().forEach(builder::configureRuntimeWiring);
 		sourceCustomizers.orderedStream().forEach((customizer) -> customizer.customize(builder));
-		try {
-			return builder.build();
-		}
-		catch (MissingSchemaException ex) {
-			throw new InvalidSchemaLocationsException(schemaLocations, resourcePatternResolver, ex);
-		}
+		return builder.build();
 	}
 
 	private Builder enableIntrospection(Builder wiring) {

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/InvalidSchemaLocationsException.java

@@ -26,7 +26,6 @@ org.springframework.boot.diagnostics.FailureAnalyzer=\
 org.springframework.boot.autoconfigure.data.redis.RedisUrlSyntaxFailureAnalyzer,\
 org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer,\
 org.springframework.boot.autoconfigure.flyway.FlywayMigrationScriptMissingFailureAnalyzer,\
-org.springframework.boot.autoconfigure.graphql.InvalidSchemaLocationsExceptionFailureAnalyzer,\
 org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer,\
 org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer,\
 org.springframework.boot.autoconfigure.jooq.NoDslContextBeanFailureAnalyzer,\