fix: use require.resolve in jest-preset (facebook#22972)

Summary:
The current way the Jest preset work requires the different files to be in `<rootDir>/node_modules/react-native`. This is not necessarily true - especially in monorepoes.

If we instead do `require.resolve`, we do not need to do `rootDir` replacement in Jest.

Having a JS file as preset has been supported since Jest 23.0.0: jestjs/jest#6185

Changelog:
----------

[General] [Fixed] - use `require.resolve` in `jest-preset`
Pull Request resolved: facebook#22972

Differential Revision: D13662758

Pulled By: hramos

fbshipit-source-id: ca79b5b89d9d05c6fe639b0d88619858e8d05da7

jest-preset.js

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+'use strict';
+
+const dir = __dirname;
+
+module.exports = {
+  haste: {
+    defaultPlatform: 'ios',
+    platforms: ['android', 'ios', 'native'],
+    hasteImplModulePath: require.resolve('./jest/hasteImpl.js'),
+    providesModuleNodeModules: ['react-native'],
+  },
+  moduleFileExtensions: ['js', 'json', 'jsx', 'node', 'ts', 'tsx'],
+  moduleNameMapper: {
+    '^React$': require.resolve('react'),
+  },
+  modulePathIgnorePatterns: [`${dir}/Libraries/react-native/`],
+  transform: {
+    '^.+\\.(js|ts|tsx)$': 'babel-jest',
+    '^.+\\.(bmp|gif|jpg|jpeg|mp4|png|psd|svg|webp)$': require.resolve(
+      './jest/assetFileTransformer.js',
+    ),
+  },
+  transformIgnorePatterns: [
+    'node_modules/(?!(jest-)?react-native|react-clone-referenced-element)',
+  ],
+  testMatch: [
+    '**/__tests__/**/*.(js|ts|tsx)',
+    '**/?(*.)+(spec|test).(js|ts|tsx)',
+  ],
+  setupFiles: [require.resolve('./jest/setup.js')],
+  testEnvironment: 'node',
+};

package.json

@@ -115,7 +115,7 @@
     "scripts/launchPackager.command",
     "scripts/packager.sh",
     "scripts/react-native-xcode.sh",
-    "jest-preset.json",
+    "jest-preset.js",
     "jest",
     "lib",
     "rn-get-polyfills.js",