Function createTransformer

packages/babel-jest/src/index.ts:166–289

  SyncTransformer<TransformerConfig>,
  TransformerConfig
> = transformerConfig => {
  const {excludeJestPreset, ...inputOptions} = transformerConfig ?? {};

  const options = {
    ...inputOptions,
    caller: {
      name: 'babel-jest',
      supportsDynamicImport: false,
      supportsExportNamespaceFrom: false,
      supportsStaticESM: false,
      supportsTopLevelAwait: false,
      ...inputOptions.caller,
    },
    compact: false,
    plugins: inputOptions.plugins ?? [],
    presets: [
      ...(inputOptions.presets ?? []),
      ...(excludeJestPreset === true ? [] : [jestPresetPath]),
    ],
    sourceMaps: 'both',
  } satisfies BabelTransformOptions;

  function mergeBabelTransformOptions(
    filename: string,
    transformOptions: JestTransformOptions,
  ): BabelTransformOptions {
    const {cwd, rootDir} = transformOptions.config;
    // `cwd` and `root` first to allow incoming options to override it
    return {
      cwd,
      root: rootDir,
      ...options,
      caller: {
        ...options.caller,
        supportsDynamicImport:
          transformOptions.supportsDynamicImport ??
          options.caller.supportsDynamicImport,
        supportsExportNamespaceFrom:
          transformOptions.supportsExportNamespaceFrom ??
          options.caller.supportsExportNamespaceFrom,
        supportsStaticESM:
          transformOptions.supportsStaticESM ??
          options.caller.supportsStaticESM,
        supportsTopLevelAwait:
          transformOptions.supportsTopLevelAwait ??
          options.caller.supportsTopLevelAwait,
      },
      filename,
    };
  }

  return {
    canInstrument: true,
    getCacheKey(sourceText, sourcePath, transformOptions) {
      const babelOptions = loadBabelConfig(
        transformOptions.config.cwd,
        sourcePath,
        mergeBabelTransformOptions(sourcePath, transformOptions),