function transform()

in packages/metro-react-native-babel-transformer/src/index.js [183:229]

• 37 lines of code
• 8 McCabe index (conditional complexity)

function transform({filename, options, src, plugins}: BabelTransformerArgs): {
  ast: BabelNodeFile,
  functionMap: ?FBSourceFunctionMap,
  ...
} {
  const OLD_BABEL_ENV = process.env.BABEL_ENV;
  process.env.BABEL_ENV = options.dev
    ? 'development'
    : process.env.BABEL_ENV || 'production';

  try {
    const babelConfig = {
      // ES modules require sourceType='module' but OSS may not always want that
      sourceType: 'unambiguous',
      ...buildBabelConfig(filename, options, plugins),
      caller: {name: 'metro', bundler: 'metro', platform: options.platform},
      ast: true,
    };
    const sourceAst =
      isTypeScriptSource(filename) ||
      isTSXSource(filename) ||
      !options.hermesParser
        ? parseSync(src, babelConfig)
        : HermesParser.parse(src, {
            babel: true,
            sourceType: babelConfig.sourceType,
          });
    /* $FlowFixMe(>=0.111.0 site=react_native_fb) This comment suppresses an
     * error found when Flow v0.111 was deployed. To see the error, delete this
     * comment and run Flow. */
    const result = transformFromAstSync(sourceAst, src, babelConfig);
    const functionMap = generateFunctionMap(sourceAst, {filename});

    // The result from `transformFromAstSync` can be null (if the file is ignored)
    if (!result) {
      /* $FlowFixMe BabelTransformer specifies that the `ast` can never be null but
       * the function returns here. Discovered when typing `BabelNode`. */
      return {ast: null, functionMap};
    }

    return {ast: nullthrows(result.ast), functionMap};
  } finally {
    if (OLD_BABEL_ENV) {
      process.env.BABEL_ENV = OLD_BABEL_ENV;
    }
  }
}