chore: migrate jest-cli to TypeScript

[SimenB]

Summary

I don't think the yargs part is typed correctly... Halp?

Built diff:

diff --git c/packages/jest-cli/build/cli/args.js w/packages/jest-cli/build/cli/args.js
index d7f22cc35..6cadf3e70 100644
--- c/packages/jest-cli/build/cli/args.js
+++ w/packages/jest-cli/build/cli/args.js
@@ -34,8 +34,6 @@ function _interopRequireDefault(obj) {
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- *
  */
 const check = argv => {
   if (argv.runInBand && argv.hasOwnProperty('maxWorkers')) {
diff --git c/packages/jest-cli/build/cli/index.js w/packages/jest-cli/build/cli/index.js
index 03d8f26a3..bb877dbfe 100644
--- c/packages/jest-cli/build/cli/index.js
+++ w/packages/jest-cli/build/cli/index.js
@@ -56,8 +56,6 @@ function _core() {
   return data;
 }
 
-var args = _interopRequireWildcard(require('./args'));
-
 function _chalk() {
   const data = _interopRequireDefault(require('chalk'));
 
@@ -100,7 +98,9 @@ function _realpathNative() {
 
 var _init = _interopRequireDefault(require('../init'));
 
-var _package = require('../../package.json');
+var _version = _interopRequireDefault(require('../version'));
+
+var args = _interopRequireWildcard(require('./args'));
 
 function _interopRequireWildcard(obj) {
   if (obj && obj.__esModule) {
@@ -202,7 +202,6 @@ function run(_x, _x2) {
 function _run() {
   _run = _asyncToGenerator(function*(maybeArgv, project) {
     try {
-      // $FlowFixMe:`allow reduced return
       const argv = buildArgv(maybeArgv);
 
       if (argv.init) {
@@ -230,18 +229,20 @@ function _run() {
 
 const buildArgv = maybeArgv => {
   const version =
-    _package.version +
+    (0, _version.default)() +
     (__dirname.includes(`packages${_path().default.sep}jest-cli`)
       ? '-dev'
       : '');
   const rawArgv = maybeArgv || process.argv.slice(2);
-  const argv = (0, _yargs().default)(rawArgv)
-    .usage(args.usage)
-    .version(version)
-    .alias('help', 'h')
-    .options(args.options)
-    .epilogue(args.docs)
-    .check(args.check).argv;
+  const argv =
+    maybeArgv ||
+    (0, _yargs().default)(process.argv.slice(2))
+      .usage(args.usage)
+      .version(version)
+      .alias('help', 'h')
+      .options(args.options)
+      .epilogue(args.docs) // @ts-ignore: it's unable to infer what arguments it contains
+      .check(args.check).argv;
   (0, _jestValidate().validateCLIOptions)(
     argv,
     _objectSpread({}, args.options, {
@@ -254,7 +255,6 @@ const buildArgv = maybeArgv => {
 
   return Object.keys(argv).reduce((result, key) => {
     if (!key.includes('-')) {
-      // $FlowFixMe:`allow reduced return
       result[key] = argv[key];
     }
 
@@ -319,7 +319,7 @@ const readResultsAndExit = (result, globalConfig) => {
               "weren't stopped in your tests. Consider running Jest with " +
               '`--detectOpenHandles` to troubleshoot this issue.'
           )
-      ); // $FlowFixMe: `unref` exists in Node
+      );
     }, 1000).unref();
   }
 };
diff --git c/packages/jest-cli/build/init/constants.js w/packages/jest-cli/build/init/constants.js
index 9b0e676be..900f23ecd 100644
--- c/packages/jest-cli/build/init/constants.js
+++ w/packages/jest-cli/build/init/constants.js
@@ -10,8 +10,6 @@ exports.JEST_CONFIG = exports.PACKAGE_JSON = void 0;
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- *
  */
 const PACKAGE_JSON = 'package.json';
 exports.PACKAGE_JSON = PACKAGE_JSON;
diff --git c/packages/jest-cli/build/init/errors.js w/packages/jest-cli/build/init/errors.js
index 77ed57202..eed7c8a66 100644
--- c/packages/jest-cli/build/init/errors.js
+++ w/packages/jest-cli/build/init/errors.js
@@ -10,14 +10,11 @@ exports.MalformedPackageJsonError = exports.NotFoundPackageJsonError = void 0;
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- *
  */
 class NotFoundPackageJsonError extends Error {
   constructor(rootDir) {
-    super();
+    super(`Could not find a "package.json" file in ${rootDir}`);
     this.name = '';
-    this.message = `Could not find a "package.json" file in ${rootDir}`;
     Error.captureStackTrace(this, () => {});
   }
 }
@@ -26,11 +23,11 @@ exports.NotFoundPackageJsonError = NotFoundPackageJsonError;
 
 class MalformedPackageJsonError extends Error {
   constructor(packageJsonPath) {
-    super();
-    this.name = '';
-    this.message =
+    super(
       `There is malformed json in ${packageJsonPath}\n` +
-      'Fix it, and then run "jest --init"';
+        'Fix it, and then run "jest --init"'
+    );
+    this.name = '';
     Error.captureStackTrace(this, () => {});
   }
 }
diff --git c/packages/jest-cli/build/init/generate_config_file.js w/packages/jest-cli/build/init/generate_config_file.js
index 4b7b0884b..44952dc9e 100644
--- c/packages/jest-cli/build/init/generate_config_file.js
+++ w/packages/jest-cli/build/init/generate_config_file.js
@@ -20,8 +20,6 @@ function _jestConfig() {
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- *
  */
 const stringifyOption = (option, map, linePrefix = '') => {
   const optionDescription = `  // ${_jestConfig().descriptions[option]}`;
@@ -69,10 +67,12 @@ const generateConfigFile = results => {
   const properties = [];
 
   for (const option in _jestConfig().descriptions) {
-    if (overrideKeys.includes(option)) {
-      properties.push(stringifyOption(option, overrides));
+    const opt = option;
+
+    if (overrideKeys.includes(opt)) {
+      properties.push(stringifyOption(opt, overrides));
     } else {
-      properties.push(stringifyOption(option, _jestConfig().defaults, '// '));
+      properties.push(stringifyOption(opt, _jestConfig().defaults, '// '));
     }
   }
 
diff --git c/packages/jest-cli/build/init/index.js w/packages/jest-cli/build/init/index.js
index 6408c62fe..cae2fc28c 100644
--- c/packages/jest-cli/build/init/index.js
+++ w/packages/jest-cli/build/init/index.js
@@ -5,30 +5,30 @@ Object.defineProperty(exports, '__esModule', {
 });
 exports.default = void 0;
 
-function _chalk() {
-  const data = _interopRequireDefault(require('chalk'));
+function _fs() {
+  const data = _interopRequireDefault(require('fs'));
 
-  _chalk = function _chalk() {
+  _fs = function _fs() {
     return data;
   };
 
   return data;
 }
 
-function _fs() {
-  const data = _interopRequireDefault(require('fs'));
+function _path() {
+  const data = _interopRequireDefault(require('path'));
 
-  _fs = function _fs() {
+  _path = function _path() {
     return data;
   };
 
   return data;
 }
 
-function _path() {
-  const data = _interopRequireDefault(require('path'));
+function _chalk() {
+  const data = _interopRequireDefault(require('chalk'));
 
-  _path = function _path() {
+  _chalk = function _chalk() {
     return data;
   };
 
@@ -202,7 +202,8 @@ var _default =
           `The following questions will help Jest to create a suitable configuration for your project\n`
         )
       );
-      let promptAborted = false;
+      let promptAborted = false; // @ts-ignore: Return type cannot be object - faulty typings
+
       const results = yield (0, _prompts().default)(questions, {
         onCancel: () => {
           promptAborted = true;
diff --git c/packages/jest-cli/build/init/modify_package_json.js w/packages/jest-cli/build/init/modify_package_json.js
index 6ecc78840..526b485b6 100644
--- c/packages/jest-cli/build/init/modify_package_json.js
+++ w/packages/jest-cli/build/init/modify_package_json.js
@@ -10,14 +10,8 @@ exports.default = void 0;
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- *
  */
-const modifyPackageJson = ({
-  projectPackageJson,
-  shouldModifyScripts,
-  hasJestProperty
-}) => {
+const modifyPackageJson = ({projectPackageJson, shouldModifyScripts}) => {
   if (shouldModifyScripts) {
     projectPackageJson.scripts
       ? (projectPackageJson.scripts.test = 'jest')
diff --git c/packages/jest-cli/build/init/questions.js w/packages/jest-cli/build/init/questions.js
index 657b5ccbf..e4790b961 100644
--- c/packages/jest-cli/build/init/questions.js
+++ w/packages/jest-cli/build/init/questions.js
@@ -10,8 +10,6 @@ exports.testScriptQuestion = exports.default = void 0;
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- *
  */
 const defaultQuestions = [
   {
diff --git c/packages/jest-cli/build/init/types.js w/packages/jest-cli/build/init/types.js
new file mode 100644
index 000000000..ad9a93a7c
--- /dev/null
+++ w/packages/jest-cli/build/init/types.js
@@ -0,0 +1 @@
+'use strict';
diff --git c/packages/jest-cli/build/version.js w/packages/jest-cli/build/version.js
index e99eee057..62f7d7cc0 100644
--- c/packages/jest-cli/build/version.js
+++ w/packages/jest-cli/build/version.js
@@ -5,16 +5,15 @@ Object.defineProperty(exports, '__esModule', {
 });
 exports.default = getVersion;
 
-var _package = require('../package.json');
-
 /**
  * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- *
  */
+const _require = require('../package.json'),
+  VERSION = _require.version;
+
 function getVersion() {
-  return _package.version;
+  return VERSION;
 }

Test plan

Green CI

[codecov-io]

Codecov Report

Merging #8024 into master will increase coverage by 0.02%.
The diff coverage is 81.81%.

@@            Coverage Diff             @@
##           master    #8024      +/-   ##
==========================================
+ Coverage   62.66%   62.68%   +0.02%     
==========================================
  Files         263      262       -1     
  Lines       10308    10311       +3     
  Branches     2281     2299      +18     
==========================================
+ Hits         6459     6463       +4     
+ Misses       3279     3277       -2     
- Partials      570      571       +1

Impacted Files	Coverage Δ
packages/jest-cli/src/init/modify_package_json.ts	100% <ø> (ø)
packages/jest-cli/src/init/constants.ts	100% <ø> (ø)
packages/jest-config/src/Deprecated.ts	66.66% <ø> (ø)	⬆️
packages/jest-cli/src/init/index.ts	83.72% <ø> (ø)
packages/jest-core/src/SearchSource.ts	57.89% <100%> (ø)	⬆️
packages/jest-config/src/utils.ts	75% <100%> (ø)	⬆️
packages/jest-cli/src/version.ts	100% <100%> (ø)
packages/jest-cli/src/init/generate_config_file.ts	100% <100%> (ø)
packages/jest-config/src/normalize.ts	79.52% <100%> (ø)	⬆️
packages/jest-cli/src/init/questions.ts	100% <100%> (ø)
... and 4 more

---

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