Merge pull request #6 from steveluscher/error-formatter

Update the error formatter

Author: taion

src/__forks__/formatRequestErrors.js

@@ -20,16 +20,20 @@ export default function formatRequestErrors(request, errors) {
   return errors.map(({locations, message}, ii) => {
     var prefix = (ii + 1) + '. ';
     var indent = ' '.repeat(prefix.length);
-    return (
-      prefix + message + '\n' +
-      locations.map(({column, line}) => {
+
+    //custom errors thrown in graphql-server may not have locations
+    var locationMessage = locations ?
+      ('\n' + locations.map(({column, line}) => {
         var queryLine = queryLines[line - 1];
         var offset = Math.min(column - 1, CONTEXT_BEFORE);
         return [
           queryLine.substr(column - 1 - offset, CONTEXT_LENGTH),
           ' '.repeat(offset) + '^^^'
         ].map(messageLine => indent + messageLine).join('\n');
-      }).join('\n')
-    );
+        }).join('\n')) :
+      '';
+
+      return prefix + message + locationMessage;
+
   }).join('\n');
 }