formatWebpackMessages.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

// Some custom utilities to prettify Webpack output.
// This is a little hacky.
// It would be easier if webpack provided a rich error object.
var friendlySyntaxErrorLabel = 'Syntax error:';
function isLikelyASyntaxError(message) {
  return message.indexOf(friendlySyntaxErrorLabel) !== -1;
}
function formatMessage(message) {
  return message
    // Make some common errors shorter:
    .replace(
      // Babel syntax error
      'Module build failed: SyntaxError:',
      friendlySyntaxErrorLabel
    )
    .replace(
      // Webpack file not found error
      /Module not found: Error: Cannot resolve 'file' or 'directory'/,
      'Module not found:'
    )
    // Internal stacks are generally useless so we strip them
    .replace(/^\s*at\s.*:\d+:\d+[\s\)]*\n/gm, '') // at ... ...:x:y
    // Webpack loader names obscure CSS filenames
    .replace('./~/css-loader!./~/postcss-loader!', '');
}

function formatWebpackMessages(stats) {
  var hasErrors = stats.hasErrors();
  var hasWarnings = stats.hasWarnings();
  if (!hasErrors && !hasWarnings) {
    return {
      errors: [],
      warnings: []
    };
  }
  // We use stats.toJson({}, true) to make output more compact and readable:
  // https://github.com/facebookincubator/create-react-app/issues/401#issuecomment-238291901
  var json = stats.toJson({}, true);
  var formattedErrors = json.errors.map(message =>
    'Error in ' + formatMessage(message)
  );
  var formattedWarnings = json.warnings.map(message =>
    'Warning in ' + formatMessage(message)
  );
  var result = {
    errors: formattedErrors,
    warnings: formattedWarnings
  };
  if (result.errors.some(isLikelyASyntaxError)) {
    // If there are any syntax errors, show just them.
    // This prevents a confusing ESLint parsing error
    // preceding a much more useful Babel syntax error.
    result.errors = result.errors.filter(isLikelyASyntaxError);
  }
  return result;
}

module.exports = formatWebpackMessages;