react/scripts/jest/devtools/setupEnv.js

'use strict';

const semver = require('semver');
const {ReactVersion} = require('../../../ReactVersions');

// DevTools stores preferences between sessions in localStorage
if (!global.hasOwnProperty('localStorage')) {
  global.localStorage = require('local-storage-fallback').default;
}

// Mimic the global we set with Webpack's DefinePlugin
global.__DEV__ = process.env.NODE_ENV !== 'production';
global.__TEST__ = true;
global.__IS_FIREFOX__ = false;
global.__IS_CHROME__ = false;
global.__IS_EDGE__ = false;

const ReactVersionTestingAgainst = process.env.REACT_VERSION || ReactVersion;

global._test_react_version = (range, testName, callback) => {
  const shouldPass = semver.satisfies(ReactVersionTestingAgainst, range);

  if (shouldPass) {
    test(testName, callback);
  } else {
    test.skip(testName, callback);
  }
};

global._test_react_version_focus = (range, testName, callback) => {
  const shouldPass = semver.satisfies(ReactVersionTestingAgainst, range);

  if (shouldPass) {
    test.only(testName, callback);
  } else {
    test.skip(testName, callback);
  }
};

global._test_ignore_for_react_version = (testName, callback) => {
  test.skip(testName, callback);
};

// Most of our tests call jest.resetModules in a beforeEach and the
// re-require all the React modules. However, the JSX runtime is injected by
// the compiler, so those bindings don't get updated. This causes warnings
// logged by the JSX runtime to not have a component stack, because component
// stack relies on the the secret internals object that lives on the React
// module, which because of the resetModules call is longer the same one.
//
// To workaround this issue, we use a proxy that re-requires the latest
// JSX Runtime from the require cache on every function invocation.
//
// Longer term we should migrate all our tests away from using require() and
// resetModules, and use import syntax instead so this kind of thing doesn't
// happen.
if (semver.gte(ReactVersionTestingAgainst, '17.0.0')) {
  lazyRequireFunctionExports('react/jsx-dev-runtime');

  // TODO: We shouldn't need to do this in the production runtime, but until
  // we remove string refs they also depend on the shared state object. Remove
  // once we remove string refs.
  lazyRequireFunctionExports('react/jsx-runtime');
}

function lazyRequireFunctionExports(moduleName) {
  jest.mock(moduleName, () => {
    return new Proxy(jest.requireActual(moduleName), {
      get(originalModule, prop) {
        // If this export is a function, return a wrapper function that lazily
        // requires the implementation from the current module cache.
        if (typeof originalModule[prop] === 'function') {
          return function () {
            return jest.requireActual(moduleName)[prop].apply(this, arguments);
          };
        } else {
          return originalModule[prop];
        }
      },
    });
  });
}