From 441f90db38e1b0c324e8d83072820359f413406c Mon Sep 17 00:00:00 2001
From: Simen Bekkhus <sbekkhus91@gmail.com>
Date: Mon, 24 Dec 2018 00:13:06 +0100
Subject: [PATCH 1/5] convert pretty-format to typescript

---
 jest.config.js                                |   2 +-
 .../jest-circus/src/formatNodeAssertErrors.js |   1 +
 packages/jest-circus/src/utils.js             |   1 +
 packages/pretty-format/package.json           |   5 +
 ...cher.test.js => AsymmetricMatcher.test.ts} |   9 +-
 ...onvertAnsi.test.js => ConvertAnsi.test.ts} |   8 +-
 ...llection.test.js => DOMCollection.test.ts} |  12 +-
 ...{DOMElement.test.js => DOMElement.test.ts} |   9 +-
 .../{Immutable.test.js => Immutable.test.ts}  |  25 ++--
 ...react.test.js.snap => react.test.tsx.snap} |   0
 .../src/__tests__/getPrettyPrint.js           |  48 -------
 ...ttyFormat.test.js => prettyFormat.test.ts} |  41 +++---
 .../{react.test.js => react.test.tsx}         |  31 +++--
 .../src/__tests__/setPrettyPrint.ts           |  56 +++++++++
 .../src/{collections.js => collections.ts}    |  15 ++-
 .../pretty-format/src/{index.js => index.ts}  |  37 +++---
 ...mmetricMatcher.js => AsymmetricMatcher.ts} |   8 +-
 .../{ConvertAnsi.js => ConvertAnsi.ts}        |  17 ++-
 .../{DOMCollection.js => DOMCollection.ts}    |  10 +-
 .../plugins/{DOMElement.js => DOMElement.ts}  |  80 ++++++------
 .../plugins/{Immutable.js => Immutable.ts}    |  14 +--
 .../{ReactElement.js => ReactElement.ts}      |  16 +--
 ...TestComponent.js => ReactTestComponent.ts} |  28 +++--
 .../lib/{escapeHTML.js => escapeHTML.ts}      |   2 -
 .../src/plugins/lib/{markup.js => markup.ts}  |   6 +-
 packages/pretty-format/src/types.ts           | 117 ++++++++++++++++++
 packages/pretty-format/tsconfig.json          |   7 ++
 yarn.lock                                     |  30 +++++
 28 files changed, 392 insertions(+), 243 deletions(-)
 rename packages/pretty-format/src/__tests__/{AsymmetricMatcher.test.js => AsymmetricMatcher.test.ts} (98%)
 rename packages/pretty-format/src/__tests__/{ConvertAnsi.test.js => ConvertAnsi.test.ts} (94%)
 rename packages/pretty-format/src/__tests__/{DOMCollection.test.js => DOMCollection.test.ts} (94%)
 rename packages/pretty-format/src/__tests__/{DOMElement.test.js => DOMElement.test.ts} (98%)
 rename packages/pretty-format/src/__tests__/{Immutable.test.js => Immutable.test.ts} (98%)
 rename packages/pretty-format/src/__tests__/__snapshots__/{react.test.js.snap => react.test.tsx.snap} (100%)
 delete mode 100644 packages/pretty-format/src/__tests__/getPrettyPrint.js
 rename packages/pretty-format/src/__tests__/{prettyFormat.test.js => prettyFormat.test.ts} (97%)
 rename packages/pretty-format/src/__tests__/{react.test.js => react.test.tsx} (97%)
 create mode 100644 packages/pretty-format/src/__tests__/setPrettyPrint.ts
 rename packages/pretty-format/src/{collections.js => collections.ts} (93%)
 rename packages/pretty-format/src/{index.js => index.ts} (95%)
 rename packages/pretty-format/src/plugins/{AsymmetricMatcher.js => AsymmetricMatcher.ts} (93%)
 rename packages/pretty-format/src/plugins/{ConvertAnsi.js => ConvertAnsi.ts} (84%)
 rename packages/pretty-format/src/plugins/{DOMCollection.js => DOMCollection.ts} (89%)
 rename packages/pretty-format/src/plugins/{DOMElement.js => DOMElement.ts} (58%)
 rename packages/pretty-format/src/plugins/{Immutable.js => Immutable.ts} (94%)
 rename packages/pretty-format/src/plugins/{ReactElement.js => ReactElement.ts} (90%)
 rename packages/pretty-format/src/plugins/{ReactTestComponent.js => ReactTestComponent.ts} (73%)
 rename packages/pretty-format/src/plugins/lib/{escapeHTML.js => escapeHTML.ts} (96%)
 rename packages/pretty-format/src/plugins/lib/{markup.js => markup.ts} (97%)
 create mode 100644 packages/pretty-format/src/types.ts
 create mode 100644 packages/pretty-format/tsconfig.json

diff --git a/jest.config.js b/jest.config.js
index 999b16dd01ca..db041ad091ae 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -38,7 +38,7 @@ module.exports = {
     '\\.snap$',
     '/packages/.*/build',
     '/packages/.*/build-es5',
-    '/packages/.*/src/__tests__/getPrettyPrint.js',
+    '/packages/.*/src/__tests__/setPrettyPrint.ts',
     '/packages/jest-cli/src/__tests__/test_root',
     '/packages/jest-cli/src/__tests__/__fixtures__/',
     '/packages/jest-cli/src/lib/__tests__/fixtures/',
diff --git a/packages/jest-circus/src/formatNodeAssertErrors.js b/packages/jest-circus/src/formatNodeAssertErrors.js
index a13caf678687..6434eee318a5 100644
--- a/packages/jest-circus/src/formatNodeAssertErrors.js
+++ b/packages/jest-circus/src/formatNodeAssertErrors.js
@@ -12,6 +12,7 @@ import type {Event, State} from 'types/Circus';
 
 import {diff, printExpected, printReceived} from 'jest-matcher-utils';
 import chalk from 'chalk';
+// $FlowFixMe: Converted to TS
 import prettyFormat from 'pretty-format';
 
 type AssertionError = {|
diff --git a/packages/jest-circus/src/utils.js b/packages/jest-circus/src/utils.js
index e8c515478694..4f079ece8c6e 100644
--- a/packages/jest-circus/src/utils.js
+++ b/packages/jest-circus/src/utils.js
@@ -28,6 +28,7 @@ import co from 'co';
 
 import StackUtils from 'stack-utils';
 
+// $FlowFixMe: Converted to TS
 import prettyFormat from 'pretty-format';
 
 import {getState} from './state';
diff --git a/packages/pretty-format/package.json b/packages/pretty-format/package.json
index c9d7fedc45b7..c90ad0715fcd 100644
--- a/packages/pretty-format/package.json
+++ b/packages/pretty-format/package.json
@@ -9,6 +9,7 @@
   "license": "MIT",
   "description": "Stringify any JavaScript value.",
   "main": "build/index.js",
+  "types": "build/index.d.ts",
   "browser": "build-es5/index.js",
   "author": "James Kyle <me@thejameskyle.com>",
   "dependencies": {
@@ -18,7 +19,11 @@
   "devDependencies": {
     "@types/ansi-regex": "^4.0.0",
     "@types/ansi-styles": "^3.2.1",
+    "@types/jest": "^24.0.0",
+    "@types/react": "*",
+    "@types/react-test-renderer": "*",
     "immutable": "4.0.0-rc.9",
+    "jest-diff": "^24.0.0",
     "react": "*",
     "react-dom": "*",
     "react-test-renderer": "*"
diff --git a/packages/pretty-format/src/__tests__/AsymmetricMatcher.test.js b/packages/pretty-format/src/__tests__/AsymmetricMatcher.test.ts
similarity index 98%
rename from packages/pretty-format/src/__tests__/AsymmetricMatcher.test.js
rename to packages/pretty-format/src/__tests__/AsymmetricMatcher.test.ts
index 7e670e57e9d2..1a25400ca982 100644
--- a/packages/pretty-format/src/__tests__/AsymmetricMatcher.test.js
+++ b/packages/pretty-format/src/__tests__/AsymmetricMatcher.test.ts
@@ -3,17 +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
  */
 
-import type {OptionsReceived} from 'types/PrettyFormat';
+import {OptionsReceived} from '../types';
+
+import prettyFormat from '../';
 
-const prettyFormat = require('../');
 const {AsymmetricMatcher} = prettyFormat.plugins;
 let options: OptionsReceived;
 
-function fnNameFor(func) {
+function fnNameFor(func: Function) {
   if (func.name) {
     return func.name;
   }
diff --git a/packages/pretty-format/src/__tests__/ConvertAnsi.test.js b/packages/pretty-format/src/__tests__/ConvertAnsi.test.ts
similarity index 94%
rename from packages/pretty-format/src/__tests__/ConvertAnsi.test.js
rename to packages/pretty-format/src/__tests__/ConvertAnsi.test.ts
index f17208681dc1..c562f67a8123 100644
--- a/packages/pretty-format/src/__tests__/ConvertAnsi.test.js
+++ b/packages/pretty-format/src/__tests__/ConvertAnsi.test.ts
@@ -3,12 +3,12 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-const ansiStyle = require('ansi-styles');
-const prettyFormat = require('../');
+import ansiStyle from 'ansi-styles';
+
+import prettyFormat from '../';
+
 const {ConvertAnsi} = prettyFormat.plugins;
 
 const prettyFormatResult = (val: string) =>
diff --git a/packages/pretty-format/src/__tests__/DOMCollection.test.js b/packages/pretty-format/src/__tests__/DOMCollection.test.ts
similarity index 94%
rename from packages/pretty-format/src/__tests__/DOMCollection.test.js
rename to packages/pretty-format/src/__tests__/DOMCollection.test.ts
index 6c08ba00308a..8cba5748f95b 100644
--- a/packages/pretty-format/src/__tests__/DOMCollection.test.js
+++ b/packages/pretty-format/src/__tests__/DOMCollection.test.ts
@@ -5,21 +5,15 @@
  * LICENSE file in the root directory of this source tree.
  *
  * @jest-environment jsdom
- * @flow
  */
 /* eslint-env browser*/
 
-'use strict';
+import prettyFormat from '../';
+import setPrettyPrint from './setPrettyPrint';
 
-const prettyFormat = require('../');
 const {DOMCollection, DOMElement} = prettyFormat.plugins;
-const toPrettyPrintTo = require('./getPrettyPrint').default([
-  DOMCollection,
-  DOMElement,
-]);
 
-const expect: any = global.expect;
-expect.extend({toPrettyPrintTo});
+setPrettyPrint([DOMCollection, DOMElement]);
 
 describe('DOMCollection plugin for object properties', () => {
   it('supports DOMStringMap', () => {
diff --git a/packages/pretty-format/src/__tests__/DOMElement.test.js b/packages/pretty-format/src/__tests__/DOMElement.test.ts
similarity index 98%
rename from packages/pretty-format/src/__tests__/DOMElement.test.js
rename to packages/pretty-format/src/__tests__/DOMElement.test.ts
index 074252ea0f77..b5e22f549c40 100644
--- a/packages/pretty-format/src/__tests__/DOMElement.test.js
+++ b/packages/pretty-format/src/__tests__/DOMElement.test.ts
@@ -5,18 +5,15 @@
  * LICENSE file in the root directory of this source tree.
  *
  * @jest-environment jsdom
- * @flow
  */
 /* eslint-env browser*/
 
-'use strict';
+import prettyFormat from '../';
+import setPrettyPrint from './setPrettyPrint';
 
-const prettyFormat = require('../');
 const {DOMElement} = prettyFormat.plugins;
-const toPrettyPrintTo = require('./getPrettyPrint').default([DOMElement]);
 
-const expect: any = global.expect;
-expect.extend({toPrettyPrintTo});
+setPrettyPrint([DOMElement]);
 
 describe('pretty-format', () => {
   // Test is not related to plugin but is related to jsdom testing environment.
diff --git a/packages/pretty-format/src/__tests__/Immutable.test.js b/packages/pretty-format/src/__tests__/Immutable.test.ts
similarity index 98%
rename from packages/pretty-format/src/__tests__/Immutable.test.js
rename to packages/pretty-format/src/__tests__/Immutable.test.ts
index e03b69dcc860..05c51241f804 100644
--- a/packages/pretty-format/src/__tests__/Immutable.test.js
+++ b/packages/pretty-format/src/__tests__/Immutable.test.ts
@@ -3,27 +3,22 @@
  *
  * 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 React from 'react';
 import Immutable from 'immutable';
-import getPrettyPrint from './getPrettyPrint';
 
-const {Immutable: ImmutablePlugin, ReactElement} = require('..').plugins;
+import setPrettyPrint from './setPrettyPrint';
+import prettyFormat from '..';
 
-const toPrettyPrintTo = getPrettyPrint([ReactElement, ImmutablePlugin]);
+const {Immutable: ImmutablePlugin, ReactElement} = prettyFormat.plugins;
 
-const expect = global.expect;
-expect.extend({toPrettyPrintTo});
+setPrettyPrint([ReactElement, ImmutablePlugin]);
 
 it('does not incorrectly match identity-obj-proxy as Immutable object', () => {
   // SENTINEL constant is from https://github.com/facebook/immutable-js
   const IS_ITERABLE_SENTINEL = '@@__IMMUTABLE_ITERABLE__@@';
-  const val = {};
+  const val: any = {};
   val[IS_ITERABLE_SENTINEL] = IS_ITERABLE_SENTINEL; // mock the mock object :)
   const expected = `{"${IS_ITERABLE_SENTINEL}": "${IS_ITERABLE_SENTINEL}"}`;
   expect(val).toPrettyPrintTo(expected, {min: true});
@@ -507,7 +502,7 @@ describe('Immutable.OrderedMap', () => {
   });
 
   it('supports non-string keys', () => {
-    const val = Immutable.OrderedMap([
+    const val = Immutable.OrderedMap<any, any>([
       [false, 'boolean'],
       ['false', 'string'],
       [0, 'number'],
@@ -871,7 +866,7 @@ describe('Immutable.Seq', () => {
   });
 
   it('supports a non-empty sequence from arguments', () => {
-    function returnArguments(...args) {
+    function returnArguments(..._args: Array<any>) {
       return arguments;
     }
     expect(Immutable.Seq(returnArguments(0, 1, 2))).toPrettyPrintTo(
@@ -933,7 +928,7 @@ describe('Immutable.Seq', () => {
 describe('Immutable.Seq lazy entries', () => {
   const expected = 'Immutable.Seq {…}';
   const object = {key0: '', key1: '1'};
-  const filterer = value => value.length !== 0;
+  const filterer = (value: string) => value.length !== 0;
 
   // undefined size confirms correct criteria for lazy Seq
   test('from object properties', () => {
@@ -951,7 +946,7 @@ describe('Immutable.Seq lazy entries', () => {
 describe('Immutable.Seq lazy values', () => {
   const expected = 'Immutable.Seq […]';
   const array = ['', '1', '22'];
-  const filterer = item => item.length !== 0;
+  const filterer = (item: string) => item.length !== 0;
 
   test('from Immutable.Range', () => {
     const val = Immutable.Range(1, Infinity);
@@ -961,7 +956,7 @@ describe('Immutable.Seq lazy values', () => {
 
   // undefined size confirms correct criteria for lazy Seq
   test('from iterator', () => {
-    function returnIterator(values) {
+    function returnIterator(values: Array<string>) {
       let i = 0;
       return {
         next() {
diff --git a/packages/pretty-format/src/__tests__/__snapshots__/react.test.js.snap b/packages/pretty-format/src/__tests__/__snapshots__/react.test.tsx.snap
similarity index 100%
rename from packages/pretty-format/src/__tests__/__snapshots__/react.test.js.snap
rename to packages/pretty-format/src/__tests__/__snapshots__/react.test.tsx.snap
diff --git a/packages/pretty-format/src/__tests__/getPrettyPrint.js b/packages/pretty-format/src/__tests__/getPrettyPrint.js
deleted file mode 100644
index 3eae13b07dbc..000000000000
--- a/packages/pretty-format/src/__tests__/getPrettyPrint.js
+++ /dev/null
@@ -1,48 +0,0 @@
-/**
- * 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.
- *
- * @flow
- */
-
-'use strict';
-
-import type {OptionsReceived, Plugins} from 'types/PrettyFormat';
-
-const diff = require('jest-diff');
-const prettyFormat = require('../');
-
-const getPrettyPrint = (plugins: Plugins) =>
-  function(received: any, expected: any, options?: OptionsReceived) {
-    const prettyFormatted = prettyFormat(received, {plugins, ...options});
-    const pass = prettyFormatted === expected;
-
-    const message = pass
-      ? () =>
-          this.utils.matcherHint('.not.toBe') +
-          '\n\n' +
-          `Expected value to not be:\n` +
-          `  ${this.utils.printExpected(expected)}\n` +
-          `Received:\n` +
-          `  ${this.utils.printReceived(prettyFormatted)}`
-      : () => {
-          const diffString = diff(expected, prettyFormatted, {
-            expand: this.expand,
-          });
-          return (
-            this.utils.matcherHint('.toBe') +
-            '\n\n' +
-            `Expected value to be:\n` +
-            `  ${this.utils.printExpected(expected)}\n` +
-            `Received:\n` +
-            `  ${this.utils.printReceived(prettyFormatted)}` +
-            (diffString ? `\n\nDifference:\n\n${diffString}` : '')
-          );
-        };
-
-    return {actual: prettyFormatted, message, pass};
-  };
-
-export default getPrettyPrint;
diff --git a/packages/pretty-format/src/__tests__/prettyFormat.test.js b/packages/pretty-format/src/__tests__/prettyFormat.test.ts
similarity index 97%
rename from packages/pretty-format/src/__tests__/prettyFormat.test.js
rename to packages/pretty-format/src/__tests__/prettyFormat.test.ts
index 339252ee9be2..779d3c45a754 100644
--- a/packages/pretty-format/src/__tests__/prettyFormat.test.js
+++ b/packages/pretty-format/src/__tests__/prettyFormat.test.ts
@@ -3,21 +3,18 @@
  *
  * 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';
-
-const prettyFormat = require('../');
+import prettyFormat from '../';
 
-function returnArguments(...args) {
+function returnArguments(..._args: Array<unknown>) {
   return arguments;
 }
 
 class MyArray<T> extends Array<T> {}
 
-function MyObject(value) {
+function MyObject(value: unknown) {
+  // @ts-ignore
   this.name = value;
 }
 
@@ -33,7 +30,7 @@ describe('prettyFormat()', () => {
   });
 
   it('prints an empty array', () => {
-    const val = [];
+    const val: never[] = [];
     expect(prettyFormat(val)).toEqual('Array []');
   });
 
@@ -94,7 +91,7 @@ describe('prettyFormat()', () => {
 
   it('prints an anonymous callback function', () => {
     let val;
-    function f(cb) {
+    function f(cb: () => void) {
       val = cb;
     }
     f(() => {});
@@ -159,7 +156,7 @@ describe('prettyFormat()', () => {
   });
 
   it('prints a map with non-string keys', () => {
-    const val = new Map([
+    const val = new Map<any, any>([
       [false, 'boolean'],
       ['false', 'string'],
       [0, 'number'],
@@ -416,7 +413,7 @@ describe('prettyFormat()', () => {
   });
 
   it('prints circular references', () => {
-    const val = {};
+    const val: any = {};
     val.prop = val;
     expect(prettyFormat(val)).toEqual('Object {\n  "prop": [Circular],\n}');
   });
@@ -488,6 +485,7 @@ describe('prettyFormat()', () => {
         'map non-empty': new Map([['name', 'value']]),
         'object literal empty': {},
         'object literal non-empty': {name: 'value'},
+        // @ts-ignore
         'object with constructor': new MyObject('value'),
         'object without constructor': Object.create(null),
         'set empty': new Set(),
@@ -519,13 +517,13 @@ describe('prettyFormat()', () => {
 
   it('throws on invalid options', () => {
     expect(() => {
-      // $FlowFixMe
+      // @ts-ignore
       prettyFormat({}, {invalidOption: true});
     }).toThrow();
   });
 
   it('supports plugins', () => {
-    function Foo() {}
+    class Foo {}
 
     expect(
       prettyFormat(new Foo(), {
@@ -548,10 +546,10 @@ describe('prettyFormat()', () => {
     const options = {
       plugins: [
         {
-          print(val) {
+          print(val: any) {
             return val.payload;
           },
-          test(val) {
+          test(val: any) {
             return val && typeof val.payload === 'string';
           },
         },
@@ -565,7 +563,7 @@ describe('prettyFormat()', () => {
     const options = {
       plugins: [
         {
-          print(val) {
+          print(val: any) {
             return val;
           },
           test() {
@@ -646,7 +644,7 @@ describe('prettyFormat()', () => {
         plugins: [
           {
             print(val, print) {
-              return val.map(item => print(item)).join(' - ');
+              return val.map((item: any) => print(item)).join(' - ');
             },
             test(val) {
               return Array.isArray(val);
@@ -663,7 +661,7 @@ describe('prettyFormat()', () => {
       prettyFormat(val, {
         plugins: [
           {
-            print(val, print) {
+            print(_val, _print) {
               return '[called]';
             },
             test(val) {
@@ -728,7 +726,7 @@ describe('prettyFormat()', () => {
 
   it('calls toJSON on Sets', () => {
     const set = new Set([1]);
-    (set: Object).toJSON = () => 'map';
+    (set as any).toJSON = () => 'map';
     expect(prettyFormat(set)).toEqual('"map"');
   });
 
@@ -736,7 +734,7 @@ describe('prettyFormat()', () => {
     const value = {apple: 'banana', toJSON: jest.fn(() => '1')};
     const name = value.toJSON.name || 'anonymous';
     const set = new Set([value]);
-    (set: Object).toJSON = jest.fn(() => 'map');
+    (set as any).toJSON = jest.fn(() => 'map');
     expect(
       prettyFormat(set, {
         callToJSON: false,
@@ -746,7 +744,7 @@ describe('prettyFormat()', () => {
         name +
         '],\n  },\n}',
     );
-    expect((set: Object).toJSON).not.toBeCalled();
+    expect((set as any).toJSON).not.toBeCalled();
     expect(value.toJSON).not.toBeCalled();
   });
 
@@ -787,6 +785,7 @@ describe('prettyFormat()', () => {
         'map non-empty': new Map([['name', 'value']]),
         'object literal empty': {},
         'object literal non-empty': {name: 'value'},
+        // @ts-ignore
         'object with constructor': new MyObject('value'),
         'object without constructor': Object.create(null),
         'set empty': new Set(),
diff --git a/packages/pretty-format/src/__tests__/react.test.js b/packages/pretty-format/src/__tests__/react.test.tsx
similarity index 97%
rename from packages/pretty-format/src/__tests__/react.test.js
rename to packages/pretty-format/src/__tests__/react.test.tsx
index 6a268319cf99..44d33d4b083e 100644
--- a/packages/pretty-format/src/__tests__/react.test.js
+++ b/packages/pretty-format/src/__tests__/react.test.tsx
@@ -3,20 +3,17 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {OptionsReceived} from 'types/PrettyFormat';
+import React from 'react';
+import renderer from 'react-test-renderer';
 
-const React = require('react');
-const renderer = require('react-test-renderer');
+import prettyFormat from '..';
+import {OptionsReceived} from '../types';
 
 const elementSymbol = Symbol.for('react.element');
 const fragmentSymbol = Symbol.for('react.fragment');
 const testSymbol = Symbol.for('react.test.json');
-
-const prettyFormat = require('..');
 const {ReactElement, ReactTestComponent} = prettyFormat.plugins;
 
 const formatElement = (element: any, options?: OptionsReceived) =>
@@ -116,7 +113,9 @@ test('supports props with numbers', () => {
 
 test('supports a single element with a function prop', () => {
   assertPrintedJSX(
-    React.createElement('Mouse', {onclick: function onclick() {}}),
+    React.createElement<{onclick: any}>('Mouse', {
+      onclick: function onclick() {},
+    }),
     '<Mouse\n  onclick={[Function onclick]}\n/>',
   );
 });
@@ -141,7 +140,7 @@ test('supports an element with and object prop and children', () => {
 
 test('supports an element with complex props and mixed children', () => {
   assertPrintedJSX(
-    React.createElement(
+    React.createElement<{customProp: any; onclick: any}>(
       'Mouse',
       {customProp: {one: '1', two: 2}, onclick: function onclick() {}},
       'HELLO',
@@ -167,11 +166,11 @@ test('escapes children properly', () => {
 
 test('supports everything all together', () => {
   assertPrintedJSX(
-    React.createElement(
+    React.createElement<{customProp: any; onclick: any}>(
       'Mouse',
       {customProp: {one: '1', two: 2}, onclick: function onclick() {}},
       'HELLO',
-      React.createElement(
+      React.createElement<{customProp: any; onclick: any}>(
         'Mouse',
         {customProp: {one: '1', two: 2}, onclick: function onclick() {}},
         'HELLO',
@@ -266,7 +265,7 @@ test('supports a single element with custom React elements with props (using ano
 });
 
 test('supports a single element with custom React elements with a child', () => {
-  function Cat(props) {
+  function Cat(props: any) {
     return React.createElement('div', props);
   }
   assertPrintedJSX(
@@ -565,7 +564,7 @@ describe('maxDepth option', () => {
 
 test('min option', () => {
   assertPrintedJSX(
-    React.createElement(
+    React.createElement<{customProp: any; onclick: any}>(
       'Mouse',
       {customProp: {one: '1', two: 2}, onclick: function onclick() {}},
       'HELLO',
@@ -622,9 +621,9 @@ test('throws if theme option is null', () => {
     'Hello, Mouse!',
   );
   expect(() => {
+    // @ts-ignore
     formatElement(jsx, {
       highlight: true,
-      // $FlowFixMe
       theme: null,
     });
   }).toThrow('pretty-format: Option "theme" must not be null.');
@@ -637,9 +636,9 @@ test('throws if theme option is not of type "object"', () => {
       {style: 'color:red'},
       'Hello, Mouse!',
     );
+    // @ts-ignore
     formatElement(jsx, {
       highlight: true,
-      // $FlowFixMe
       theme: 'beautiful',
     });
   }).toThrow(
@@ -701,7 +700,7 @@ test('ReactTestComponent plugin highlights syntax with color from theme option',
 });
 
 test('supports forwardRef with a child', () => {
-  function Cat(props) {
+  function Cat(props: any) {
     return React.createElement('div', props, props.children);
   }
 
diff --git a/packages/pretty-format/src/__tests__/setPrettyPrint.ts b/packages/pretty-format/src/__tests__/setPrettyPrint.ts
new file mode 100644
index 000000000000..4a8a562bf52b
--- /dev/null
+++ b/packages/pretty-format/src/__tests__/setPrettyPrint.ts
@@ -0,0 +1,56 @@
+/**
+ * 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.
+ */
+
+// @ts-ignore
+import diff from 'jest-diff';
+
+import prettyFormat from '../';
+import {OptionsReceived, Plugins} from '../types';
+
+declare global {
+  namespace jest {
+    interface Matchers<R> {
+      toPrettyPrintTo(expected: any, options?: OptionsReceived): R;
+    }
+  }
+}
+
+const setPrettyPrint = (plugins: Plugins) => {
+  expect.extend({
+    toPrettyPrintTo(received: any, expected: any, options?: OptionsReceived) {
+      const prettyFormatted = prettyFormat(received, {plugins, ...options});
+      const pass = prettyFormatted === expected;
+
+      const message = pass
+        ? () =>
+            this.utils.matcherHint('.not.toBe') +
+            '\n\n' +
+            `Expected value to not be:\n` +
+            `  ${this.utils.printExpected(expected)}\n` +
+            `Received:\n` +
+            `  ${this.utils.printReceived(prettyFormatted)}`
+        : () => {
+            const diffString = diff(expected, prettyFormatted, {
+              expand: this.expand,
+            });
+            return (
+              this.utils.matcherHint('.toBe') +
+              '\n\n' +
+              `Expected value to be:\n` +
+              `  ${this.utils.printExpected(expected)}\n` +
+              `Received:\n` +
+              `  ${this.utils.printReceived(prettyFormatted)}` +
+              (diffString ? `\n\nDifference:\n\n${diffString}` : '')
+            );
+          };
+
+      return {actual: prettyFormatted, message, pass};
+    },
+  });
+};
+
+export default setPrettyPrint;
diff --git a/packages/pretty-format/src/collections.js b/packages/pretty-format/src/collections.ts
similarity index 93%
rename from packages/pretty-format/src/collections.js
rename to packages/pretty-format/src/collections.ts
index ec0478b488f3..28112d1117b5 100644
--- a/packages/pretty-format/src/collections.js
+++ b/packages/pretty-format/src/collections.ts
@@ -4,17 +4,16 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @flow
  */
 
-import type {Config, Printer, Refs} from 'types/PrettyFormat';
+import {Config, Printer, Refs} from './types';
 
 const getKeysOfEnumerableProperties = (object: Object) => {
-  const keys = Object.keys(object).sort();
+  const keys: Array<string | symbol> = Object.keys(object).sort();
 
   if (Object.getOwnPropertySymbols) {
     Object.getOwnPropertySymbols(object).forEach(symbol => {
-      //$FlowFixMe because property enumerable is missing in undefined
+      // @ts-ignore: because property enumerable is missing in undefined
       if (Object.getOwnPropertyDescriptor(object, symbol).enumerable) {
         keys.push(symbol);
       }
@@ -180,7 +179,13 @@ export function printObjectProperties(
     for (let i = 0; i < keys.length; i++) {
       const key = keys[i];
       const name = printer(key, config, indentationNext, depth, refs);
-      const value = printer(val[key], config, indentationNext, depth, refs);
+      const value = printer(
+        (val as any)[key],
+        config,
+        indentationNext,
+        depth,
+        refs,
+      );
 
       result += indentationNext + name + ': ' + value;
 
diff --git a/packages/pretty-format/src/index.js b/packages/pretty-format/src/index.ts
similarity index 95%
rename from packages/pretty-format/src/index.js
rename to packages/pretty-format/src/index.ts
index bea132820a4e..6b9858e3dae6 100644
--- a/packages/pretty-format/src/index.js
+++ b/packages/pretty-format/src/index.ts
@@ -3,23 +3,20 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {
+import style from 'ansi-styles';
+import {
   Colors,
   Config,
   Options,
   OptionsReceived,
+  NewPlugin,
   Plugin,
   Plugins,
   Refs,
-  StringOrNull,
   Theme,
-} from 'types/PrettyFormat';
-
-import style from 'ansi-styles';
+} from './types';
 
 import {
   printIteratorEntries,
@@ -44,18 +41,18 @@ const symbolToString = Symbol.prototype.toString;
 
 // Explicitly comparing typeof constructor to function avoids undefined as name
 // when mock identity-obj-proxy returns the key as the value for any key.
-const getConstructorName = val =>
+const getConstructorName = (val: any) =>
   (typeof val.constructor === 'function' && val.constructor.name) || 'Object';
 
 // Is val is equal to global window object? Works even if it does not exist :)
 /* global window */
-const isWindow = val => typeof window !== 'undefined' && val === window;
+const isWindow = (val: any) => typeof window !== 'undefined' && val === window;
 
 const SYMBOL_REGEXP = /^Symbol\((.*)\)(.*)$/;
 const NEWLINE_REGEXP = /\n/gi;
 
 class PrettyFormatPluginError extends Error {
-  constructor(message, stack) {
+  constructor(message: string, stack: string) {
     super(message);
     this.stack = stack;
     this.name = this.constructor.name;
@@ -103,7 +100,7 @@ function printBasicValue(
   printFunctionName: boolean,
   escapeRegex: boolean,
   escapeString: boolean,
-): StringOrNull {
+): string | null {
   if (val === true || val === false) {
     return '' + val;
   }
@@ -254,6 +251,10 @@ function printComplexValue(
         '}';
 }
 
+function isNewPlugin(plugin: Plugin): plugin is NewPlugin {
+  return (plugin as NewPlugin).serialize != null;
+}
+
 function printPlugin(
   plugin: Plugin,
   val: any,
@@ -265,7 +266,7 @@ function printPlugin(
   let printed;
 
   try {
-    printed = plugin.serialize
+    printed = isNewPlugin(plugin)
       ? plugin.serialize(val, config, indentation, depth, refs, printer)
       : plugin.print(
           val,
@@ -392,13 +393,12 @@ function validateOptions(options: OptionsReceived) {
 }
 
 const getColorsHighlight = (options: OptionsReceived): Colors =>
-  // $FlowFixMe: Flow thinks keys from `Colors` are missing from `DEFAULT_THEME_KEYS`
   DEFAULT_THEME_KEYS.reduce((colors, key) => {
     const value =
-      options.theme && options.theme[key] !== undefined
-        ? options.theme[key]
-        : DEFAULT_THEME[key];
-    const color = style[value];
+      options.theme && (options.theme as any)[key] !== undefined
+        ? (options.theme as any)[key]
+        : (DEFAULT_THEME as any)[key];
+    const color = (style as any)[value];
     if (
       color &&
       typeof color.close === 'string' &&
@@ -414,7 +414,6 @@ const getColorsHighlight = (options: OptionsReceived): Colors =>
   }, Object.create(null));
 
 const getColorsEmpty = (): Colors =>
-  // $FlowFixMe: Flow thinks keys from `Colors` are missing from `DEFAULT_THEME_KEYS`
   DEFAULT_THEME_KEYS.reduce((colors, key) => {
     colors[key] = {close: '', open: ''};
     return colors;
@@ -506,4 +505,4 @@ prettyFormat.plugins = {
   ReactTestComponent,
 };
 
-module.exports = prettyFormat;
+export = prettyFormat;
diff --git a/packages/pretty-format/src/plugins/AsymmetricMatcher.js b/packages/pretty-format/src/plugins/AsymmetricMatcher.ts
similarity index 93%
rename from packages/pretty-format/src/plugins/AsymmetricMatcher.js
rename to packages/pretty-format/src/plugins/AsymmetricMatcher.ts
index 3d6376c732fe..83fe8a7cf4d6 100644
--- a/packages/pretty-format/src/plugins/AsymmetricMatcher.js
+++ b/packages/pretty-format/src/plugins/AsymmetricMatcher.ts
@@ -3,11 +3,9 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {Config, NewPlugin, Printer, Refs} from 'types/PrettyFormat';
+import {Config, NewPlugin, Printer, Refs} from '../types';
 
 import {printListItems, printObjectProperties} from '../collections';
 
@@ -90,4 +88,6 @@ export const serialize = (
 
 export const test = (val: any) => val && val.$$typeof === asymmetricMatcher;
 
-export default ({serialize, test}: NewPlugin);
+const plugin: NewPlugin = {serialize, test};
+
+export default plugin;
diff --git a/packages/pretty-format/src/plugins/ConvertAnsi.js b/packages/pretty-format/src/plugins/ConvertAnsi.ts
similarity index 84%
rename from packages/pretty-format/src/plugins/ConvertAnsi.js
rename to packages/pretty-format/src/plugins/ConvertAnsi.ts
index b974b47aef88..5a673342ce0d 100644
--- a/packages/pretty-format/src/plugins/ConvertAnsi.js
+++ b/packages/pretty-format/src/plugins/ConvertAnsi.ts
@@ -3,17 +3,14 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {Config, Printer, NewPlugin, Refs} from 'types/PrettyFormat';
-
 import ansiRegex from 'ansi-regex';
 import style from 'ansi-styles';
+import {Config, Printer, NewPlugin, Refs} from '../types';
 
-const toHumanReadableAnsi = text =>
-  text.replace(ansiRegex(), (match, offset, string) => {
+const toHumanReadableAnsi = (text: string) =>
+  text.replace(ansiRegex(), match => {
     switch (match) {
       case style.red.close:
       case style.green.close:
@@ -59,8 +56,8 @@ const toHumanReadableAnsi = text =>
     }
   });
 
-export const test = (val: any) =>
-  typeof val === 'string' && val.match(ansiRegex());
+export const test = (val: any): boolean =>
+  typeof val === 'string' && !!val.match(ansiRegex());
 
 export const serialize = (
   val: string,
@@ -71,4 +68,6 @@ export const serialize = (
   printer: Printer,
 ) => printer(toHumanReadableAnsi(val), config, indentation, depth, refs);
 
-export default ({serialize, test}: NewPlugin);
+const plugin: NewPlugin = {serialize, test};
+
+export default plugin;
diff --git a/packages/pretty-format/src/plugins/DOMCollection.js b/packages/pretty-format/src/plugins/DOMCollection.ts
similarity index 89%
rename from packages/pretty-format/src/plugins/DOMCollection.js
rename to packages/pretty-format/src/plugins/DOMCollection.ts
index b45975022286..e922cc1bd9f9 100644
--- a/packages/pretty-format/src/plugins/DOMCollection.js
+++ b/packages/pretty-format/src/plugins/DOMCollection.ts
@@ -3,11 +3,9 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {Config, NewPlugin, Printer, Refs} from 'types/PrettyFormat';
+import {Config, NewPlugin, Printer, Refs} from '../types';
 
 import {printListItems, printObjectProperties} from '../collections';
 
@@ -26,7 +24,7 @@ export const test = (val: any) =>
   testName(val.constructor.name);
 
 // Convert array of attribute objects to props object.
-const propsReducer = (props, attribute) => {
+const propsReducer = (props: any, attribute: any) => {
   props[attribute.name] = attribute.value;
   return props;
 };
@@ -72,4 +70,6 @@ export const serialize = (
   );
 };
 
-export default ({serialize, test}: NewPlugin);
+const plugin: NewPlugin = {serialize, test};
+
+export default plugin;
diff --git a/packages/pretty-format/src/plugins/DOMElement.js b/packages/pretty-format/src/plugins/DOMElement.ts
similarity index 58%
rename from packages/pretty-format/src/plugins/DOMElement.js
rename to packages/pretty-format/src/plugins/DOMElement.ts
index f9e86164ad15..03546fb210fb 100644
--- a/packages/pretty-format/src/plugins/DOMElement.js
+++ b/packages/pretty-format/src/plugins/DOMElement.ts
@@ -3,11 +3,9 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {Config, NewPlugin, Printer, Refs} from 'types/PrettyFormat';
+import {Config, NewPlugin, Printer, Refs} from '../types';
 
 import {
   printChildren,
@@ -18,30 +16,6 @@ import {
   printText,
 } from './lib/markup';
 
-type Attribute = {
-  name: string,
-  value: string,
-};
-
-type Element = {
-  attributes: Array<Attribute>,
-  childNodes: Array<Element | Text | Comment>,
-  nodeType: 1,
-  tagName: string,
-};
-type Text = {
-  data: string,
-  nodeType: 3,
-};
-type Comment = {
-  data: string,
-  nodeType: 8,
-};
-type DocumentFragment = {
-  children: Array<Element>,
-  nodeType: 11,
-};
-
 const ELEMENT_NODE = 1;
 const TEXT_NODE = 3;
 const COMMENT_NODE = 8;
@@ -61,33 +35,39 @@ export const test = (val: any) =>
   val.constructor.name &&
   testNode(val.nodeType, val.constructor.name);
 
-// Convert array of attribute objects to keys array and props object.
-const keysMapper = attribute => attribute.name;
-const propsReducer = (props, attribute) => {
-  props[attribute.name] = attribute.value;
-  return props;
-};
+type HandledType = Element | Text | Comment | DocumentFragment;
+
+function nodeIsText(node: HandledType): node is Text {
+  return node.nodeType === TEXT_NODE;
+}
+
+function nodeIsComment(node: HandledType): node is Comment {
+  return node.nodeType === COMMENT_NODE;
+}
+
+function nodeIsFragment(node: HandledType): node is DocumentFragment {
+  return node.nodeType === FRAGMENT_NODE;
+}
 
 export const serialize = (
-  node: Element | Text | Comment | DocumentFragment,
+  node: HandledType,
   config: Config,
   indentation: string,
   depth: number,
   refs: Refs,
   printer: Printer,
 ): string => {
-  if (node.nodeType === TEXT_NODE) {
+  if (nodeIsText(node)) {
     return printText(node.data, config);
   }
 
-  if (node.nodeType === COMMENT_NODE) {
+  if (nodeIsComment(node)) {
     return printComment(node.data, config);
   }
 
-  const type =
-    node.nodeType === FRAGMENT_NODE
-      ? `DocumentFragment`
-      : node.tagName.toLowerCase();
+  const type = nodeIsFragment(node)
+    ? `DocumentFragment`
+    : node.tagName.toLowerCase();
 
   if (++depth > config.maxDepth) {
     return printElementAsLeaf(type, config);
@@ -96,8 +76,20 @@ export const serialize = (
   return printElement(
     type,
     printProps(
-      Array.prototype.map.call(node.attributes || [], keysMapper).sort(),
-      Array.prototype.reduce.call(node.attributes || [], propsReducer, {}),
+      nodeIsFragment(node)
+        ? []
+        : Array.from(node.attributes)
+            .map(attr => attr.name)
+            .sort(),
+      nodeIsFragment(node)
+        ? []
+        : Array.from(node.attributes).reduce(
+            (props, attribute) => {
+              props[attribute.name] = attribute.value;
+              return props;
+            },
+            {} as any,
+          ),
       config,
       indentation + config.indent,
       depth,
@@ -117,4 +109,6 @@ export const serialize = (
   );
 };
 
-export default ({serialize, test}: NewPlugin);
+const plugin: NewPlugin = {serialize, test};
+
+export default plugin;
diff --git a/packages/pretty-format/src/plugins/Immutable.js b/packages/pretty-format/src/plugins/Immutable.ts
similarity index 94%
rename from packages/pretty-format/src/plugins/Immutable.js
rename to packages/pretty-format/src/plugins/Immutable.ts
index 3814b7d832a0..85a415731a49 100644
--- a/packages/pretty-format/src/plugins/Immutable.js
+++ b/packages/pretty-format/src/plugins/Immutable.ts
@@ -3,11 +3,9 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {Config, Printer, NewPlugin, Refs} from 'types/PrettyFormat';
+import {Config, Printer, NewPlugin, Refs} from '../types';
 import {printIteratorEntries, printIteratorValues} from '../collections';
 
 // SENTINEL constants are from https://github.com/facebook/immutable-js
@@ -21,8 +19,8 @@ const IS_SEQ_SENTINEL = '@@__IMMUTABLE_SEQ__@@';
 const IS_SET_SENTINEL = '@@__IMMUTABLE_SET__@@';
 const IS_STACK_SENTINEL = '@@__IMMUTABLE_STACK__@@';
 
-const getImmutableName = name => 'Immutable.' + name;
-const printAsLeaf = name => '[' + name + ']';
+const getImmutableName = (name: string) => 'Immutable.' + name;
+const printAsLeaf = (name: string) => '[' + name + ']';
 const SPACE = ' ';
 const LAZY = '…'; // Seq is lazy if it calls a method like filter
 
@@ -52,7 +50,7 @@ const printImmutableEntries = (
 
 // Record has an entries method because it is a collection in immutable v3.
 // Return an iterator for Immutable Record from version v3 or v4.
-const getRecordEntries = val => {
+const getRecordEntries = (val: any) => {
   let i = 0;
   return {
     next() {
@@ -239,4 +237,6 @@ export const test = (val: any) =>
   val &&
   (val[IS_ITERABLE_SENTINEL] === true || val[IS_RECORD_SENTINEL] === true);
 
-export default ({serialize, test}: NewPlugin);
+const plugin: NewPlugin = {serialize, test};
+
+export default plugin;
diff --git a/packages/pretty-format/src/plugins/ReactElement.js b/packages/pretty-format/src/plugins/ReactElement.ts
similarity index 90%
rename from packages/pretty-format/src/plugins/ReactElement.js
rename to packages/pretty-format/src/plugins/ReactElement.ts
index eef452ce9525..aa05d4ebf72e 100644
--- a/packages/pretty-format/src/plugins/ReactElement.js
+++ b/packages/pretty-format/src/plugins/ReactElement.ts
@@ -3,11 +3,9 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {Config, NewPlugin, Printer, Refs} from 'types/PrettyFormat';
+import {Config, NewPlugin, Printer, Refs} from '../types';
 
 import {
   printChildren,
@@ -24,7 +22,7 @@ const contextSymbol = Symbol.for('react.context');
 
 // Given element.props.children, or subtree during recursive traversal,
 // return flattened array of children.
-const getChildren = (arg, children = []) => {
+const getChildren = (arg: any[], children = []) => {
   if (Array.isArray(arg)) {
     arg.forEach(item => {
       getChildren(item, children);
@@ -35,7 +33,7 @@ const getChildren = (arg, children = []) => {
   return children;
 };
 
-const getType = element => {
+const getType = (element: any) => {
   const type = element.type;
   if (typeof type === 'string') {
     return type;
@@ -66,7 +64,7 @@ const getType = element => {
   return 'UNDEFINED';
 };
 
-const getPropKeys = element => {
+const getPropKeys = (element: any) => {
   const {props} = element;
 
   return Object.keys(props)
@@ -75,7 +73,7 @@ const getPropKeys = element => {
 };
 
 export const serialize = (
-  element: React$Element<any>,
+  element: any,
   config: Config,
   indentation: string,
   depth: number,
@@ -109,4 +107,6 @@ export const serialize = (
 
 export const test = (val: any) => val && val.$$typeof === elementSymbol;
 
-export default ({serialize, test}: NewPlugin);
+const plugin: NewPlugin = {serialize, test};
+
+export default plugin;
diff --git a/packages/pretty-format/src/plugins/ReactTestComponent.js b/packages/pretty-format/src/plugins/ReactTestComponent.ts
similarity index 73%
rename from packages/pretty-format/src/plugins/ReactTestComponent.js
rename to packages/pretty-format/src/plugins/ReactTestComponent.ts
index 159602bd79b8..c380fbfc3e81 100644
--- a/packages/pretty-format/src/plugins/ReactTestComponent.js
+++ b/packages/pretty-format/src/plugins/ReactTestComponent.ts
@@ -3,17 +3,19 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {
-  Config,
-  Printer,
-  NewPlugin,
-  ReactTestObject,
-  Refs,
-} from 'types/PrettyFormat';
+import {Config, Printer, NewPlugin, Refs} from '../types';
+
+export type ReactTestObject = {
+  $$typeof: Symbol;
+  type: string;
+  props?: Object;
+  children?: null | Array<ReactTestChild>;
+};
+
+// Child can be `number` in Stack renderer but not in Fiber renderer.
+type ReactTestChild = ReactTestObject | string | number;
 
 import {
   printChildren,
@@ -24,12 +26,12 @@ import {
 
 const testSymbol = Symbol.for('react.test.json');
 
-const getPropKeys = object => {
+const getPropKeys = (object: ReactTestObject) => {
   const {props} = object;
 
   return props
     ? Object.keys(props)
-        .filter(key => props[key] !== undefined)
+        .filter(key => (props as any)[key] !== undefined)
         .sort()
     : [];
 };
@@ -73,4 +75,6 @@ export const serialize = (
 
 export const test = (val: any) => val && val.$$typeof === testSymbol;
 
-export default ({serialize, test}: NewPlugin);
+const plugin: NewPlugin = {serialize, test};
+
+export default plugin;
diff --git a/packages/pretty-format/src/plugins/lib/escapeHTML.js b/packages/pretty-format/src/plugins/lib/escapeHTML.ts
similarity index 96%
rename from packages/pretty-format/src/plugins/lib/escapeHTML.js
rename to packages/pretty-format/src/plugins/lib/escapeHTML.ts
index 2fd80a074e32..e4c17104269e 100644
--- a/packages/pretty-format/src/plugins/lib/escapeHTML.js
+++ b/packages/pretty-format/src/plugins/lib/escapeHTML.ts
@@ -3,8 +3,6 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
 export default function escapeHTML(str: string): string {
diff --git a/packages/pretty-format/src/plugins/lib/markup.js b/packages/pretty-format/src/plugins/lib/markup.ts
similarity index 97%
rename from packages/pretty-format/src/plugins/lib/markup.js
rename to packages/pretty-format/src/plugins/lib/markup.ts
index ee346d73c6ef..c5ab6a786091 100644
--- a/packages/pretty-format/src/plugins/lib/markup.js
+++ b/packages/pretty-format/src/plugins/lib/markup.ts
@@ -3,18 +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
  */
 
-import type {Config, Printer, Refs} from 'types/PrettyFormat';
+import {Config, Printer, Refs} from '../../types';
 
 import escapeHTML from './escapeHTML';
 
 // Return empty string if keys is empty.
 export const printProps = (
   keys: Array<string>,
-  props: Object,
+  props: any,
   config: Config,
   indentation: string,
   depth: number,
diff --git a/packages/pretty-format/src/types.ts b/packages/pretty-format/src/types.ts
new file mode 100644
index 000000000000..89d06d5bd418
--- /dev/null
+++ b/packages/pretty-format/src/types.ts
@@ -0,0 +1,117 @@
+/**
+ * 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.
+ */
+
+export type Colors = {
+  comment: {close: string; open: string};
+  content: {close: string; open: string};
+  prop: {close: string; open: string};
+  tag: {close: string; open: string};
+  value: {close: string; open: string};
+};
+type Indent = (arg0: string) => string;
+export type Refs = Array<any>;
+type Print = (arg0: any) => string;
+
+export type Theme = {
+  comment: string;
+  content: string;
+  prop: string;
+  tag: string;
+  value: string;
+};
+
+type ThemeReceived = {
+  comment?: string;
+  content?: string;
+  prop?: string;
+  tag?: string;
+  value?: string;
+};
+
+export type Options = {
+  callToJSON: boolean;
+  escapeRegex: boolean;
+  escapeString: boolean;
+  highlight: boolean;
+  indent: number;
+  maxDepth: number;
+  min: boolean;
+  plugins: Plugins;
+  printFunctionName: boolean;
+  theme: Theme;
+};
+
+export type OptionsReceived = {
+  callToJSON?: boolean;
+  escapeRegex?: boolean;
+  escapeString?: boolean;
+  highlight?: boolean;
+  indent?: number;
+  maxDepth?: number;
+  min?: boolean;
+  plugins?: Plugins;
+  printFunctionName?: boolean;
+  theme?: ThemeReceived;
+};
+
+export type Config = {
+  callToJSON: boolean;
+  colors: Colors;
+  escapeRegex: boolean;
+  escapeString: boolean;
+  indent: string;
+  maxDepth: number;
+  min: boolean;
+  plugins: Plugins;
+  printFunctionName: boolean;
+  spacingInner: string;
+  spacingOuter: string;
+};
+
+export type Printer = (
+  val: any,
+  config: Config,
+  indentation: string,
+  depth: number,
+  refs: Refs,
+  hasCalledToJSON?: boolean,
+) => string;
+
+type Test = (arg0: any) => boolean;
+
+export type NewPlugin = {
+  serialize: (
+    val: any,
+    config: Config,
+    indentation: string,
+    depth: number,
+    refs: Refs,
+    printer: Printer,
+  ) => string;
+  test: Test;
+};
+
+type PluginOptions = {
+  edgeSpacing: string;
+  min: boolean;
+  spacing: string;
+};
+
+type OldPlugin = {
+  print: (
+    val: any,
+    print: Print,
+    indent: Indent,
+    options: PluginOptions,
+    colors: Colors,
+  ) => string;
+  test: Test;
+};
+
+export type Plugin = NewPlugin | OldPlugin;
+
+export type Plugins = Array<Plugin>;
diff --git a/packages/pretty-format/tsconfig.json b/packages/pretty-format/tsconfig.json
new file mode 100644
index 000000000000..7bb06bce6d20
--- /dev/null
+++ b/packages/pretty-format/tsconfig.json
@@ -0,0 +1,7 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "build"
+  }
+}
diff --git a/yarn.lock b/yarn.lock
index ffc57a710145..6b1c4ffc6978 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1640,6 +1640,11 @@
   resolved "https://registry.yarnpkg.com/@types/jest/-/jest-23.3.12.tgz#7e0ced251fa94c3bc2d1023d4b84b2992fa06376"
   integrity sha512-/kQvbVzdEpOq4tEWT79yAHSM4nH4xMlhJv2GrLVQt4Qmo8yYsPdioBM1QpN/2GX1wkfMnyXvdoftvLUr0LBj7Q==
 
+"@types/jest@^24.0.0":
+  version "24.0.0"
+  resolved "https://registry.yarnpkg.com/@types/jest/-/jest-24.0.0.tgz#848492026c327b3548d92be0352a545c36a21e8a"
+  integrity sha512-kOafJnUTnMd7/OfEO/x3I47EHswNjn+dbz9qk3mtonr1RvKT+1FGVxnxAx08I9K8Tl7j9hpoJRE7OCf+t10fng==
+
 "@types/jsdom@^11.12.0":
   version "11.12.0"
   resolved "https://registry.yarnpkg.com/@types/jsdom/-/jsdom-11.12.0.tgz#00ddc6f0a1b04c2f5ff6fb23eb59360ca65f12ae"
@@ -1703,11 +1708,31 @@
   resolved "https://registry.yarnpkg.com/@types/prompts/-/prompts-1.2.0.tgz#891e73f735ad5e82e8adae3a99424128e105fb62"
   integrity sha512-7JXpT2rSd4hqd2oBWU1wfEW6x6gX+qPH+gLzGEx+My3wcb67K9Rc02xNQRVn67phusmXm5Yqn4oTP2OW1G5zdQ==
 
+"@types/prop-types@*":
+  version "15.5.8"
+  resolved "https://registry.yarnpkg.com/@types/prop-types/-/prop-types-15.5.8.tgz#8ae4e0ea205fe95c3901a5a1df7f66495e3a56ce"
+  integrity sha512-3AQoUxQcQtLHsK25wtTWIoIpgYjH3vSDroZOUr7PpCHw/jLY1RB9z9E8dBT/OSmwStVgkRNvdh+ZHNiomRieaw==
+
 "@types/q@^1.5.1":
   version "1.5.1"
   resolved "https://registry.yarnpkg.com/@types/q/-/q-1.5.1.tgz#48fd98c1561fe718b61733daed46ff115b496e18"
   integrity sha512-eqz8c/0kwNi/OEHQfvIuJVLTst3in0e7uTKeuY+WL/zfKn0xVujOTp42bS/vUUokhK5P2BppLd9JXMOMHcgbjA==
 
+"@types/react-test-renderer@*":
+  version "16.0.3"
+  resolved "https://registry.yarnpkg.com/@types/react-test-renderer/-/react-test-renderer-16.0.3.tgz#cce5c983d66cc5c3582e7c2f44b274ab635a8acc"
+  integrity sha512-NWOAxVQeJxpXuNKgw83Hah0nquiw1nUexM9qY/Hk3a+XhZwgMtaa6GLA9E1TKMT75Odb3/KE/jiBO4enTuEJjQ==
+  dependencies:
+    "@types/react" "*"
+
+"@types/react@*":
+  version "16.8.1"
+  resolved "https://registry.yarnpkg.com/@types/react/-/react-16.8.1.tgz#b431b104ecc6febda170b718caa9f50be66a6750"
+  integrity sha512-tD1ETKJcuhANOejRc/p7OgQ16DKnbGi0M3LccelKlPnUCDp2a5koVxZFoRN9HN+A+m84HB5VGN7I+r3nNhS3PA==
+  dependencies:
+    "@types/prop-types" "*"
+    csstype "^2.2.0"
+
 "@types/resolve@*":
   version "0.0.8"
   resolved "https://registry.yarnpkg.com/@types/resolve/-/resolve-0.0.8.tgz#f26074d238e02659e323ce1a13d041eee280e194"
@@ -4115,6 +4140,11 @@ cssstyle@^1.0.0:
   dependencies:
     cssom "0.3.x"
 
+csstype@^2.2.0:
+  version "2.6.2"
+  resolved "https://registry.yarnpkg.com/csstype/-/csstype-2.6.2.tgz#3043d5e065454579afc7478a18de41909c8a2f01"
+  integrity sha512-Rl7PvTae0pflc1YtxtKbiSqq20Ts6vpIYOD5WBafl4y123DyHUeLrRdQP66sQW8/6gmX8jrYJLXwNeMqYVJcow==
+
 currently-unhandled@^0.4.1:
   version "0.4.1"
   resolved "https://registry.yarnpkg.com/currently-unhandled/-/currently-unhandled-0.4.1.tgz#988df33feab191ef799a61369dd76c17adf957ea"

From c0331c1814e6f5996f546296ba5c4ffb53c584bb Mon Sep 17 00:00:00 2001
From: Simen Bekkhus <sbekkhus91@gmail.com>
Date: Wed, 6 Feb 2019 10:20:36 +0100
Subject: [PATCH 2/5] changelog

---
 CHANGELOG.md     | 1 +
 scripts/build.js | 4 +---
 scripts/watch.js | 4 +---
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d039d87a4441..fa44400ddb21 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 ### Chore & Maintenance
 
 - `[*]`: Setup building, linting and testing of TypeScript ([#7808](https://github.com/facebook/jest/pull/7808))
+- `[pretty-format]`: Migrate to TypeScript ([#7809](https://github.com/facebook/jest/pull/7809))
 
 ### Performance
 
diff --git a/scripts/build.js b/scripts/build.js
index 78d67bdbec5f..9afc50653ad6 100644
--- a/scripts/build.js
+++ b/scripts/build.js
@@ -196,9 +196,7 @@ function compileTypes(packages) {
     fs.existsSync(path.resolve(p, 'tsconfig.json'))
   );
 
-  if (packageWithTs.length > 0) {
-    execa.sync('tsc', ['-b', ...packageWithTs]);
-  }
+  execa.sync('tsc', ['-b', ...packageWithTs]);
 }
 
 if (files.length) {
diff --git a/scripts/watch.js b/scripts/watch.js
index b40d670643b5..d2ab88c9791a 100644
--- a/scripts/watch.js
+++ b/scripts/watch.js
@@ -61,9 +61,7 @@ const packageWithTs = packages.filter(p =>
   fs.existsSync(path.resolve(p, 'tsconfig.json'))
 );
 
-if (packageWithTs.length > 0) {
-  execa('tsc', ['-b', ...packageWithTs, '--watch']);
-}
+execa('tsc', ['-b', ...packageWithTs, '--watch']);
 
 setInterval(() => {
   const files = Array.from(filesToBuild.keys());

From 67e2488b18cc874d2f5d028747bee854680a5b3f Mon Sep 17 00:00:00 2001
From: Orta Therox <orta.therox@gmail.com>
Date: Wed, 6 Feb 2019 11:24:21 -0500
Subject: [PATCH 3/5] Adds some inline docs to the exported methods

---
 packages/pretty-format/src/collections.ts | 32 ++++++++++++++---------
 packages/pretty-format/src/index.ts       | 21 ++++++++++++---
 2 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/packages/pretty-format/src/collections.ts b/packages/pretty-format/src/collections.ts
index 28112d1117b5..87afa9fe74fb 100644
--- a/packages/pretty-format/src/collections.ts
+++ b/packages/pretty-format/src/collections.ts
@@ -23,9 +23,11 @@ const getKeysOfEnumerableProperties = (object: Object) => {
   return keys;
 };
 
-// Return entries (for example, of a map)
-// with spacing, indentation, and comma
-// without surrounding punctuation (for example, braces)
+/**
+ * Return entries (for example, of a map)
+ * with spacing, indentation, and comma
+ * without surrounding punctuation (for example, braces)
+ */
 export function printIteratorEntries(
   // Flow 0.51.0: property `@@iterator` of $Iterator not found in Object
   // To allow simplistic getRecordIterator in immutable.js
@@ -82,9 +84,11 @@ export function printIteratorEntries(
   return result;
 }
 
-// Return values (for example, of a set)
-// with spacing, indentation, and comma
-// without surrounding punctuation (braces or brackets)
+/**
+ * Return values (for example, of a set)
+ * with spacing, indentation, and comma
+ * without surrounding punctuation (braces or brackets)
+ */
 export function printIteratorValues(
   iterator: Iterator<any>,
   config: Config,
@@ -121,9 +125,11 @@ export function printIteratorValues(
   return result;
 }
 
-// Return items (for example, of an array)
-// with spacing, indentation, and comma
-// without surrounding punctuation (for example, brackets)
+/**
+ *  Return items (for example, of an array)
+ * with spacing, indentation, and comma
+ * without surrounding punctuation (for example, brackets)
+ **/
 export function printListItems(
   list: any,
   config: Config,
@@ -157,9 +163,11 @@ export function printListItems(
   return result;
 }
 
-// Return properties of an object
-// with spacing, indentation, and comma
-// without surrounding punctuation (for example, braces)
+/**
+ * Return properties of an object
+ * with spacing, indentation, and comma
+ * without surrounding punctuation (for example, braces)
+ */
 export function printObjectProperties(
   val: Object,
   config: Config,
diff --git a/packages/pretty-format/src/index.ts b/packages/pretty-format/src/index.ts
index 6b9858e3dae6..856504521ac1 100644
--- a/packages/pretty-format/src/index.ts
+++ b/packages/pretty-format/src/index.ts
@@ -39,13 +39,15 @@ const errorToString = Error.prototype.toString;
 const regExpToString = RegExp.prototype.toString;
 const symbolToString = Symbol.prototype.toString;
 
-// Explicitly comparing typeof constructor to function avoids undefined as name
-// when mock identity-obj-proxy returns the key as the value for any key.
+/**
+ * Explicitly comparing typeof constructor to function avoids undefined as name
+ * when mock identity-obj-proxy returns the key as the value for any key.
+ */
 const getConstructorName = (val: any) =>
   (typeof val.constructor === 'function' && val.constructor.name) || 'Object';
 
-// Is val is equal to global window object? Works even if it does not exist :)
 /* global window */
+/** Is val is equal to global window object? Works even if it does not exist :) */
 const isWindow = (val: any) => typeof window !== 'undefined' && val === window;
 
 const SYMBOL_REGEXP = /^Symbol\((.*)\)(.*)$/;
@@ -95,6 +97,10 @@ function printError(val: Error): string {
   return '[' + errorToString.call(val) + ']';
 }
 
+/**
+ * The first port of call for printing an object, handles most of the
+ * data-types in JS.
+ */
 function printBasicValue(
   val: any,
   printFunctionName: boolean,
@@ -167,6 +173,10 @@ function printBasicValue(
   return null;
 }
 
+/**
+ * Handles more complex objects ( such as objects with circular references.
+ * maps and sets etc )
+ */
 function printComplexValue(
   val: any,
   config: Config,
@@ -471,6 +481,11 @@ function createIndent(indent: number): string {
   return new Array(indent + 1).join(' ');
 }
 
+/**
+ * Returns a presentation string of your `val` object
+ * @param val any potential JavaScript object
+ * @param options Custom settings
+ */
 function prettyFormat(val: any, options?: OptionsReceived): string {
   if (options) {
     validateOptions(options);

From a37f6b11ca139618ef8d36473f607ab7bb4e9225 Mon Sep 17 00:00:00 2001
From: Simen Bekkhus <sbekkhus91@gmail.com>
Date: Wed, 6 Feb 2019 20:20:53 +0100
Subject: [PATCH 4/5] Update collections.ts

---
 packages/pretty-format/src/collections.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/pretty-format/src/collections.ts b/packages/pretty-format/src/collections.ts
index 87afa9fe74fb..7a95502fbd9c 100644
--- a/packages/pretty-format/src/collections.ts
+++ b/packages/pretty-format/src/collections.ts
@@ -126,7 +126,7 @@ export function printIteratorValues(
 }
 
 /**
- *  Return items (for example, of an array)
+ * Return items (for example, of an array)
  * with spacing, indentation, and comma
  * without surrounding punctuation (for example, brackets)
  **/

From 5cfdf4c8dcc59fc059b2e03c4901b5d7adc1eec7 Mon Sep 17 00:00:00 2001
From: Simen Bekkhus <sbekkhus91@gmail.com>
Date: Wed, 6 Feb 2019 21:33:44 +0100
Subject: [PATCH 5/5] tweak types

---
 packages/pretty-format/src/__tests__/AsymmetricMatcher.test.ts | 2 +-
 packages/pretty-format/src/collections.ts                      | 3 +--
 packages/pretty-format/src/index.ts                            | 2 +-
 3 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/packages/pretty-format/src/__tests__/AsymmetricMatcher.test.ts b/packages/pretty-format/src/__tests__/AsymmetricMatcher.test.ts
index 1a25400ca982..b46d96ba5565 100644
--- a/packages/pretty-format/src/__tests__/AsymmetricMatcher.test.ts
+++ b/packages/pretty-format/src/__tests__/AsymmetricMatcher.test.ts
@@ -12,7 +12,7 @@ import prettyFormat from '../';
 const {AsymmetricMatcher} = prettyFormat.plugins;
 let options: OptionsReceived;
 
-function fnNameFor(func: Function) {
+function fnNameFor(func: (...any: any[]) => any) {
   if (func.name) {
     return func.name;
   }
diff --git a/packages/pretty-format/src/collections.ts b/packages/pretty-format/src/collections.ts
index 7a95502fbd9c..305e5c0da3d6 100644
--- a/packages/pretty-format/src/collections.ts
+++ b/packages/pretty-format/src/collections.ts
@@ -13,8 +13,7 @@ const getKeysOfEnumerableProperties = (object: Object) => {
 
   if (Object.getOwnPropertySymbols) {
     Object.getOwnPropertySymbols(object).forEach(symbol => {
-      // @ts-ignore: because property enumerable is missing in undefined
-      if (Object.getOwnPropertyDescriptor(object, symbol).enumerable) {
+      if (Object.getOwnPropertyDescriptor(object, symbol)!.enumerable) {
         keys.push(symbol);
       }
     });
diff --git a/packages/pretty-format/src/index.ts b/packages/pretty-format/src/index.ts
index 856504521ac1..9ed723356e42 100644
--- a/packages/pretty-format/src/index.ts
+++ b/packages/pretty-format/src/index.ts
@@ -43,7 +43,7 @@ const symbolToString = Symbol.prototype.toString;
  * Explicitly comparing typeof constructor to function avoids undefined as name
  * when mock identity-obj-proxy returns the key as the value for any key.
  */
-const getConstructorName = (val: any) =>
+const getConstructorName = (val: new (...args: any[]) => any) =>
   (typeof val.constructor === 'function' && val.constructor.name) || 'Object';
 
 /* global window */