Function transformCode

packager/src/JSTransformer/worker/worker.js:65–138

(
  transformer: Transformer,
  filename: string,
  sourceCode: string,
  options: Options,
  callback: Callback,
)

) => mixed;

function transformCode(
  transformer: Transformer,
  filename: string,
  sourceCode: string,
  options: Options,
  callback: Callback,
) {
  invariant(
    !options.minify || options.transform.generateSourceMaps,
    'Minifying source code requires the `generateSourceMaps` option to be `true`',
  );

  const isJson = filename.endsWith('.json');
  if (isJson) {
    sourceCode = 'module.exports=' + sourceCode;
  }

  const transformFileStartLogEntry = {
    action_name: 'Transforming file',
    action_phase: 'start',
    file_name: filename,
    log_entry_label: 'Transforming file',
    start_timestamp: process.hrtime(),
  };

  let transformed;
  try {
    transformed = transformer.transform(sourceCode, filename, options.transform);
  } catch (error) {
    callback(error);
    return;
  }

  invariant(
    transformed != null,
    'Missing transform results despite having no error.',
  );

  var code, map;
  if (options.minify) {
    ({code, map} =
      constantFolding(filename, inline(filename, transformed, options)));
    invariant(code != null, 'Missing code from constant-folding transform.');
  } else {
    ({code, map} = transformed);
  }

  if (isJson) {
    code = code.replace(/^\w+\.exports=/, '');
  } else {
    // Remove shebang
    code = code.replace(/^#!.*/, '');
  }

  const depsResult = isJson
    ? {dependencies: [], dependencyOffsets: []}
    : extractDependencies(code);