Migrate jest-leak-detector to TypeScript (jestjs#7825)

CHANGELOG.md

@@ -12,6 +12,7 @@
 - `[jest-get-type]`: Migrate to TypeScript ([#7818](https://github.com/facebook/jest/pull/7818))
 - `[jest-regex-util]`: Migrate to TypeScript ([#7822](https://github.com/facebook/jest/pull/7822))
 - `[jest-diff]`: Migrate to TypeScript ([#7824](https://github.com/facebook/jest/pull/7824))
+- `[jest-leak-detector]`: Migrate to TypeScript ([#7825](https://github.com/facebook/jest/pull/7825))
 
 ### Performance
 

packages/jest-leak-detector/package.json

@@ -8,6 +8,7 @@
   },
   "license": "MIT",
   "main": "build/index.js",
+  "types": "build/index.d.ts",
   "dependencies": {
     "pretty-format": "^24.0.0"
   },

packages/jest-leak-detector/src/__tests__/index.test.js → packages/jest-leak-detector/src/__tests__/index.test.ts

@@ -73,8 +73,8 @@ it('tests different objects', () => {
 });
 
 it('correctly checks more complex leaks', () => {
-  let ref1 = {};
-  let ref2 = {};
+  let ref1: any = {};
+  let ref2: any = {};
 
   // Create a circular dependency between ref1 and ref2.
   ref1.ref2 = ref2;

packages/jest-leak-detector/src/index.js → packages/jest-leak-detector/src/index.ts

@@ -3,20 +3,16 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-'use strict';
-
-import prettyFormat from 'pretty-format';
 import v8 from 'v8';
 import vm from 'vm';
+import prettyFormat from 'pretty-format';
 
 export default class {
-  _isReferenceBeingHeld: boolean;
+  private _isReferenceBeingHeld: boolean;
 
-  constructor(value: ?Object) {
+  constructor(value: unknown) {
     if (this._isPrimitive(value)) {
       throw new TypeError(
         [
@@ -55,7 +51,7 @@ export default class {
     return this._isReferenceBeingHeld;
   }
 
-  _runGarbageCollector() {
+  private _runGarbageCollector() {
     const isGarbageCollectorHidden = !global.gc;
 
     // GC is usually hidden, so we have to expose it before running.
@@ -68,7 +64,7 @@ export default class {
     }
   }
 
-  _isPrimitive(value: any): boolean {
+  private _isPrimitive(value: unknown): boolean {
     return value !== Object(value);
   }
 }

packages/jest-leak-detector/tsconfig.json

@@ -0,0 +1,10 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "build"
+  },
+  "references": [
+    {"path": "../pretty-format"}
+  ]
+}