message: Have arrays of errors output message if available
diff: @@ -1073,16 +1073,18 @@ GraphiQL.formatResult = function(result) {
  return JSON.stringify(result, null, 2);
  };
  -GraphiQL.formatError = function(error) {
  - const formattedError = JSON.stringify(error, null, 2);
  - if (formattedError === '{}' && error.message) {
  - return JSON.stringify(
  - { message: error.message, stack: error.stack },
  - null,
  - 2,
  - );
  - }
  - return formattedError;
  +const formatSingleError = error => ({
  + ...error,
  + // Raise these details even if they're non-enumerable
  + message: error.message,
  + stack: error.stack,
  +});
  +
  +GraphiQL.formatError = function(rawError) {
  + const result = Array.isArray(rawError)
  + ? rawError.map(formatSingleError)
  + : formatSingleError(rawError);
  + return JSON.stringify(result, null, 2);
  };
  const defaultQuery = `# Welcome to GraphiQL
  