Check if inner exception is of type GraphQLError in DefaultGraphQLErrorHandler

src/main/java/graphql/servlet/DefaultGraphQLErrorHandler.java

@@ -44,6 +44,9 @@ protected List<GraphQLError> filterGraphQLErrors(List<GraphQLError> errors) {
     }
 
     protected boolean isClientError(GraphQLError error) {
-        return !(error instanceof ExceptionWhileDataFetching || error instanceof Throwable);
+        if (error instanceof ExceptionWhileDataFetching) {
+            return ((ExceptionWhileDataFetching) error).getException() instanceof GraphQLError;
+        }
+        return !(error instanceof Throwable);
     }
 }

src/test/groovy/graphql/servlet/GraphQLServletSpec.groovy

@@ -641,6 +641,23 @@ class GraphQLServletSpec extends Specification {
             errors.first().message.startsWith("Internal Server Error(s)")
     }
 
+    def "errors that also implement GraphQLError thrown while data fetching are passed to caller"() {
+        setup:
+            servlet = createServlet({ throw new TestGraphQLErrorException("This is a test message") })
+            request.addParameter('query', 'query { echo(arg:"test") }')
+
+        when:
+            servlet.doGet(request, response)
+
+        then:
+            response.getStatus() == STATUS_OK
+            response.getContentType() == CONTENT_TYPE_JSON_UTF8
+            def errors = getResponseContent().errors
+            errors.size() == 1
+            errors.first().extensions.foo == "bar"
+            errors.first().message.startsWith("Exception while fetching data (/echo) : This is a test message")
+    }
+
     def "batched errors while data fetching are masked in the response"() {
         setup:
             servlet = createServlet({ throw new TestException() })

src/test/groovy/graphql/servlet/TestGraphQLErrorException.groovy

@@ -0,0 +1,32 @@
+package graphql.servlet
+
+import graphql.ErrorType
+import graphql.GraphQLError
+import graphql.language.SourceLocation
+
+/**
+ * @author Andrew Potter
+ */
+class TestGraphQLErrorException extends RuntimeException implements GraphQLError {
+
+    public TestGraphQLErrorException(String message) {
+        super(message);
+    }
+
+    @Override
+    public Map<String, Object> getExtensions() {
+        Map<String, Object> customAttributes = new LinkedHashMap<>();
+        customAttributes.put("foo", "bar");
+        return customAttributes;
+    }
+
+    @Override
+    List<SourceLocation> getLocations() {
+        return null
+    }
+
+    @Override
+    ErrorType getErrorType() {
+        return ErrorType.ValidationError;
+    }
+}