Allow configuring schema through GraphQlSource customizer

As of gh-117, the GraphQlAutoConfiguration throws an exception if no
schema file was found while scanning configured locations.
This prevents developers from manually configuring the schema using
`GraphQlSourceBuilderCustomizer` instances.

This commit ensures that a `MissingSchemaException` is only raised if no
schema was configured at the time we're building the actual
GraphQlSource.

This exception is later wrapped by the GraphQlAutoConfiguration to raise
an `InvalidSchemaLocationsException` with useful information about
configured schema locations.

Fixes gh-124

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

@@ -38,6 +38,7 @@ import org.springframework.core.io.Resource;
 import org.springframework.core.io.support.ResourcePatternResolver;
 import org.springframework.graphql.execution.DataFetcherExceptionResolver;
 import org.springframework.graphql.execution.GraphQlSource;
+import org.springframework.graphql.execution.MissingSchemaException;
 import org.springframework.graphql.execution.RuntimeWiringConfigurer;
 
 /**
@@ -71,7 +72,12 @@ public class GraphQlAutoConfiguration {
 				.instrumentation(instrumentationsProvider.orderedStream().collect(Collectors.toList()));
 		wiringConfigurers.orderedStream().forEach(builder::configureRuntimeWiring);
 		sourceCustomizers.orderedStream().forEach((customizer) -> customizer.customize(builder));
-		return builder.build();
+		try {
+			return builder.build();
+		}
+		catch (MissingSchemaException exc) {
+			throw new InvalidSchemaLocationsException(properties.getSchema().getLocations(), resourcePatternResolver, exc);
+		}
 	}
 
 	private List<Resource> resolveSchemaResources(ResourcePatternResolver resolver, List<String> schemaLocations) throws IOException {
@@ -86,9 +92,6 @@ public class GraphQlAutoConfiguration {
 				}
 			}
 		}
-		if (schemaResources.isEmpty()) {
-			throw new MissingSchemaException(schemaLocations, resolver);
-		}
 		return schemaResources;
 	}
 

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

@@ -21,18 +21,25 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
+import org.springframework.core.NestedRuntimeException;
 import org.springframework.core.io.support.ResourcePatternResolver;
 
 /**
- * {@link MissingSchemaException} thrown when no schema can be found in the provided locations.
+ * {@link InvalidSchemaLocationsException} thrown when no schema file could be found in the provided locations.
  *
  * @author Brian Clozel
+ * @since 1.0.0
  */
-public class MissingSchemaException extends RuntimeException {
+public class InvalidSchemaLocationsException extends NestedRuntimeException {
 
 	private final List<SchemaLocation> schemaLocations;
 
-	public MissingSchemaException(List<String> locations, ResourcePatternResolver resolver) {
+	public InvalidSchemaLocationsException(List<String> locations, ResourcePatternResolver resolver) {
+		this(locations, resolver, null);
+	}
+
+	public InvalidSchemaLocationsException(List<String> locations, ResourcePatternResolver resolver, Throwable cause) {
+		super("No schema file could be found in the provided locations.", cause);
 		List<SchemaLocation> providedLocations = new ArrayList<>();
 		for (String location : locations) {
 			try {

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

@@ -21,17 +21,17 @@ import org.springframework.boot.diagnostics.FailureAnalysis;
 
 /**
  * An implementation of {@link AbstractFailureAnalyzer} to analyze failures caused by
- * {@link MissingSchemaException}.
+ * {@link InvalidSchemaLocationsException}.
  *
  * @author Brian Clozel
  */
-class MissingSchemaExceptionFailureAnalyzer extends AbstractFailureAnalyzer<MissingSchemaException> {
+class InvalidSchemaLocationsExceptionFailureAnalyzer extends AbstractFailureAnalyzer<InvalidSchemaLocationsException> {
 
 	@Override
-	protected FailureAnalysis analyze(Throwable rootFailure, MissingSchemaException cause) {
+	protected FailureAnalysis analyze(Throwable rootFailure, InvalidSchemaLocationsException 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()) {
+		for (InvalidSchemaLocationsException.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

@@ -11,7 +11,7 @@ org.springframework.graphql.boot.data.GraphQlWebFluxQuerydslAutoConfiguration
 
 # Failure Analyzers
 org.springframework.boot.diagnostics.FailureAnalyzer=\
-org.springframework.graphql.boot.MissingSchemaExceptionFailureAnalyzer
+org.springframework.graphql.boot.InvalidSchemaLocationsExceptionFailureAnalyzer
 
 # Spring Test @AutoConfigureGraphQlTester
 org.springframework.graphql.boot.test.tester.AutoConfigureGraphQlTester=\

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

@@ -25,6 +25,7 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.graphql.execution.GraphQlSource;
+import org.springframework.graphql.execution.MissingSchemaException;
 
 import static org.assertj.core.api.Assertions.assertThat;