react/scripts/jest/preprocessor.js

'use strict';

const path = require('path');

const babel = require('@babel/core');
const coffee = require('coffee-script');

const tsPreprocessor = require('./typescript/preprocessor');
const createCacheKeyFunction = require('fbjs-scripts/jest/createCacheKeyFunction');

const pathToBabel = path.join(
  require.resolve('@babel/core'),
  '../..',
  'package.json'
);
const pathToBabelPluginReplaceConsoleCalls = require.resolve(
  '../babel/transform-replace-console-calls'
);
const pathToBabelPluginAsyncToGenerator = require.resolve(
  '@babel/plugin-transform-async-to-generator'
);
const pathToTransformInfiniteLoops = require.resolve(
  '../babel/transform-prevent-infinite-loops'
);
const pathToTransformTestGatePragma = require.resolve(
  '../babel/transform-test-gate-pragma'
);
const pathToBabelrc = path.join(__dirname, '..', '..', 'babel.config.js');
const pathToErrorCodes = require.resolve('../error-codes/codes.json');

const babelOptions = {
  plugins: [
    // For Node environment only. For builds, Rollup takes care of ESM.
    require.resolve('@babel/plugin-transform-modules-commonjs'),

    // Keep stacks detailed in tests.
    // Don't put this in .babelrc so that we don't embed filenames
    // into ReactART builds that include JSX.
    // TODO: I have not verified that this actually works.
    require.resolve('@babel/plugin-transform-react-jsx-source'),

    pathToTransformInfiniteLoops,
    pathToTransformTestGatePragma,

    // This optimization is important for extremely performance-sensitive (e.g. React source).
    // It's okay to disable it for tests.
    [
      require.resolve('@babel/plugin-transform-block-scoping'),
      {throwIfClosureRequired: false},
    ],
  ],
  retainLines: true,
};

module.exports = {
  process: function(src, filePath) {
    if (filePath.match(/\.css$/)) {
      // Don't try to parse CSS modules; they aren't needed for tests anyway.
      return '';
    }
    if (filePath.match(/\.coffee$/)) {
      return coffee.compile(src, {bare: true});
    }
    if (filePath.match(/\.ts$/) && !filePath.match(/\.d\.ts$/)) {
      return tsPreprocessor.compile(src, filePath);
    }
    if (filePath.match(/\.json$/)) {
      return src;
    }
    if (!filePath.match(/\/third_party\//)) {
      // for test files, we also apply the async-await transform, but we want to
      // make sure we don't accidentally apply that transform to product code.
      const isTestFile = !!filePath.match(/\/__tests__\//);
      const isInDevToolsPackages = !!filePath.match(
        /\/packages\/react-devtools.*\//
      );
      const testOnlyPlugins = [pathToBabelPluginAsyncToGenerator];
      const sourceOnlyPlugins = [];
      if (process.env.NODE_ENV === 'development' && !isInDevToolsPackages) {
        sourceOnlyPlugins.push(pathToBabelPluginReplaceConsoleCalls);
      }
      const plugins = (isTestFile ? testOnlyPlugins : sourceOnlyPlugins).concat(
        babelOptions.plugins
      );
      return babel.transform(
        src,
        Object.assign(
          {filename: path.relative(process.cwd(), filePath)},
          babelOptions,
          {
            plugins,
          }
        )
      );
    }
    return src;
  },

  getCacheKey: createCacheKeyFunction([
    __filename,
    pathToBabel,
    pathToBabelrc,
    pathToTransformInfiniteLoops,
    pathToTransformTestGatePragma,
    pathToErrorCodes,
  ]),
};