function mergeConfig()

in packages/metro-config/src/loadConfig.js [99:168]

• 51 lines of code
• 14 McCabe index (conditional complexity)

function mergeConfig<T: InputConfigT>(
  defaultConfig: T,
  ...configs: Array<InputConfigT>
): T {
  // If the file is a plain object we merge the file with the default config,
  // for the function we don't do this since that's the responsibility of the user
  return configs.reduce(
    (totalConfig, nextConfig) => ({
      ...totalConfig,
      ...nextConfig,

      cacheStores:
        nextConfig.cacheStores != null
          ? typeof nextConfig.cacheStores === 'function'
            ? nextConfig.cacheStores(MetroCache)
            : nextConfig.cacheStores
          : totalConfig.cacheStores,

      resolver: {
        /* $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. */
        ...totalConfig.resolver,
        ...(nextConfig.resolver || {}),
        dependencyExtractor:
          nextConfig.resolver && nextConfig.resolver.dependencyExtractor != null
            ? resolve(nextConfig.resolver.dependencyExtractor)
            : totalConfig.resolver.dependencyExtractor,
        hasteImplModulePath:
          nextConfig.resolver && nextConfig.resolver.hasteImplModulePath != null
            ? resolve(nextConfig.resolver.hasteImplModulePath)
            : totalConfig.resolver.hasteImplModulePath,
      },
      serializer: {
        /* $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. */
        ...totalConfig.serializer,
        ...(nextConfig.serializer || {}),
      },
      transformer: {
        /* $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. */
        ...totalConfig.transformer,
        ...(nextConfig.transformer || {}),
        babelTransformerPath:
          nextConfig.transformer &&
          nextConfig.transformer.babelTransformerPath != null
            ? resolve(nextConfig.transformer.babelTransformerPath)
            : totalConfig.transformer.babelTransformerPath,
      },
      server: {
        /* $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. */
        ...totalConfig.server,
        ...(nextConfig.server || {}),
      },
      symbolicator: {
        /* $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. */
        ...totalConfig.symbolicator,
        ...(nextConfig.symbolicator || {}),
      },
    }),
    defaultConfig,
  );
}