Add FailureAnalyzer for schema location issues

Prior to this commit, the schema locations configured with
`spring.graphql.schema.locations` could fail in several cases:
* one of the provided locations cannot be resolved as a Resource
* none of the provided locations holds an actual schema file

The latter can happen if several classpath locations match a given
location and the wrong one is considered first.

This commit introduces a new `MissingSchemaException` that holds the
locations information. We're adding the relevant FailureAnalyzer to help
developers troubleshoot such configurations issues.

Fixes gh-117

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

@@ -24,6 +24,8 @@ import java.util.stream.Collectors;
 
 import graphql.GraphQL;
 import graphql.execution.instrumentation.Instrumentation;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
@@ -51,6 +53,8 @@ import org.springframework.graphql.execution.RuntimeWiringConfigurer;
 @EnableConfigurationProperties(GraphQlProperties.class)
 public class GraphQlAutoConfiguration {
 
+	private static final Log logger = LogFactory.getLog(GraphQlAutoConfiguration.class);
+
 	private static final String[] SCHEMA_FILES_EXTENSIONS = new String[] {"*.graphqls", "*.graphql", "*.gql", "*.gqls"};
 
 	@Bean
@@ -74,9 +78,17 @@ public class GraphQlAutoConfiguration {
 		List<Resource> schemaResources = new ArrayList<>();
 		for (String location : schemaLocations) {
 			for (String extension : SCHEMA_FILES_EXTENSIONS) {
-				schemaResources.addAll(Arrays.asList(resolver.getResources(location + extension)));
+				try {
+					schemaResources.addAll(Arrays.asList(resolver.getResources(location + extension)));
+				}
+				catch (IOException ex) {
+					logger.debug("Could not resolve schema location: '" + location + extension + "'", ex);
+				}
 			}
 		}
+		if (schemaResources.isEmpty()) {
+			throw new MissingSchemaException(schemaLocations, resolver);
+		}
 		return schemaResources;
 	}
 

graphql-spring-boot-starter/src/main/java/org/springframework/graphql/boot/MissingSchemaException.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2020-2021 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.graphql.boot;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.core.io.support.ResourcePatternResolver;
+
+/**
+ * {@link MissingSchemaException} thrown when no schema can be found in the provided locations.
+ *
+ * @author Brian Clozel
+ */
+public class MissingSchemaException extends RuntimeException {
+
+	private final List<SchemaLocation> schemaLocations;
+
+	public MissingSchemaException(List<String> locations, ResourcePatternResolver resolver) {
+		List<SchemaLocation> providedLocations = new ArrayList<>();
+		for (String location : locations) {
+			try {
+				String uri = resolver.getResource(location).getURI().toASCIIString();
+				providedLocations.add(new SchemaLocation(location, uri));
+			}
+			catch (IOException ex) {
+				providedLocations.add(new SchemaLocation(location, ""));
+			}
+		}
+		this.schemaLocations = Collections.unmodifiableList(providedLocations);
+	}
+
+	/**
+	 * Return the list of provided locations where to look for schemas.
+	 */
+	public List<SchemaLocation> getSchemaLocations() {
+		return this.schemaLocations;
+	}
+
+	/**
+	 * The location where to look for schemas.
+	 */
+	public static class SchemaLocation {
+
+		private final String location;
+
+		private final String uri;
+
+		SchemaLocation(String location, String uri) {
+			this.location = location;
+			this.uri = uri;
+		}
+
+		/**
+		 * Return the location String to be resolved by a {@link ResourcePatternResolver}.
+		 */
+		public String getLocation() {
+			return this.location;
+		}
+
+		/**
+		 * Return the resolved URI String for this location, an empty String if resolution failed.
+		 */
+		public String getUri() {
+			return this.uri;
+		}
+	}
+}

graphql-spring-boot-starter/src/main/java/org/springframework/graphql/boot/MissingSchemaExceptionFailureAnalyzer.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2020-2021 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.graphql.boot;
+
+import org.springframework.boot.diagnostics.AbstractFailureAnalyzer;
+import org.springframework.boot.diagnostics.FailureAnalysis;
+
+/**
+ * An implementation of {@link AbstractFailureAnalyzer} to analyze failures caused by
+ * {@link MissingSchemaException}.
+ *
+ * @author Brian Clozel
+ */
+class MissingSchemaExceptionFailureAnalyzer extends AbstractFailureAnalyzer<MissingSchemaException> {
+
+	@Override
+	protected FailureAnalysis analyze(Throwable rootFailure, MissingSchemaException cause) {
+		String message = "Could not find any GraphQL schema file under configured locations.";
+		StringBuilder action = new StringBuilder("Check that the following locations contain schema files: " + System.lineSeparator());
+		for (MissingSchemaException.SchemaLocation schemaLocation : cause.getSchemaLocations()) {
+			action.append(String.format("- '%s' (%s)"  + System.lineSeparator(), schemaLocation.getUri(), schemaLocation.getLocation()));
+		}
+		return new FailureAnalysis(message, action.toString(), cause);
+	}
+}

graphql-spring-boot-starter/src/main/resources/META-INF/spring.factories

@@ -9,6 +9,10 @@ org.springframework.graphql.boot.security.GraphQlWebMvcSecurityAutoConfiguration
 org.springframework.graphql.boot.data.GraphQlWebMvcQuerydslAutoConfiguration,\
 org.springframework.graphql.boot.data.GraphQlWebFluxQuerydslAutoConfiguration
 
+# Failure Analyzers
+org.springframework.boot.diagnostics.FailureAnalyzer=\
+org.springframework.graphql.boot.MissingSchemaExceptionFailureAnalyzer
+
 # Spring Test @AutoConfigureGraphQlTester
 org.springframework.graphql.boot.test.tester.AutoConfigureGraphQlTester=\
 org.springframework.graphql.boot.test.tester.WebTestClientMockMvcAutoConfiguration,\

graphql-spring-boot-starter/src/test/java/org/springframework/graphql/boot/GraphQlAutoConfigurationTests.java

@@ -40,7 +40,7 @@ class GraphQlAutoConfigurationTests {
 	void shouldFailWhenSchemaFileIsMissing() {
 		this.contextRunner.run((context) -> {
 			assertThat(context).hasFailed();
-			assertThat(context).getFailure().getRootCause().hasMessage("'schemaResources' should not be empty");
+			assertThat(context).getFailure().getRootCause().isInstanceOf(MissingSchemaException.class);
 		});
 	}