Expose this.equals to custom matchers.

docs/en/ExpectAPI.md

@@ -73,6 +73,10 @@ These helper functions can be found on `this` inside a custom matcher:
 
 A boolean to let you know this matcher was called with the negated `.not` modifier allowing you to flip your assertion.
 
+#### `this.equals(a, b)`
+
+This is a deep-equality function that will return `true` if two objects have the same values (recursively).
+
 #### `this.utils`
 
 There are a number of helpful tools exposed on `this.utils` primarily consisting of the exports from [`jest-matcher-utils`](https://github.com/facebook/jest/tree/master/packages/jest-matcher-utils).

packages/jest-matchers/src/__tests__/extend-test.js

@@ -10,6 +10,7 @@
 
 'use strict';
 
+const {equals} = require('../jasmine-utils');
 const jestExpect = require('../');
 const matcherUtils = require('jest-matcher-utils');
 
@@ -60,3 +61,16 @@ it('is ok if there is no message specified', () => {
     jestExpect(true).toFailWithoutMessage(),
   ).toThrowErrorMatchingSnapshot();
 });
+
+it('exposes an equality function to custom matchers', () => {
+  // jestExpect and expect share the same global state
+  expect.assertions(3);
+  jestExpect.extend({
+    toBeOne() {
+      expect(this.equals).toBe(equals);
+      return {pass: !!this.equals(1, 1)};
+    },
+  });
+
+  expect(() => jestExpect().toBeOne()).not.toThrow();
+});

packages/jest-matchers/src/index.js

@@ -14,7 +14,7 @@ import type {
   Expect,
   ExpectationObject,
   ExpectationResult,
-  MatcherContext,
+  MatcherState,
   MatchersObject,
   RawMatcherFn,
   ThrowingMatcherFn,
@@ -24,7 +24,7 @@ import type {
 const matchers = require('./matchers');
 const spyMatchers = require('./spyMatchers');
 const toThrowMatchers = require('./toThrowMatchers');
-
+const {equals} = require('./jasmine-utils');
 const utils = require('jest-matcher-utils');
 const {
   any,
@@ -194,7 +194,7 @@ const makeThrowingMatcher = (
 ): ThrowingMatcherFn => {
   return function throwingMatcher(...args) {
     let throws = true;
-    const matcherContext: MatcherContext = Object.assign(
+    const matcherContext: MatcherState = Object.assign(
       // When throws is disabled, the matcher will not throw errors during test
       // execution but instead add them to the global matcher state. If a
       // matcher throws, test execution is normally stopped immediately. The
@@ -203,6 +203,7 @@ const makeThrowingMatcher = (
       {dontThrow: () => (throws = false)},
       global[GLOBAL_STATE].state,
       {
+        equals,
         isNot,
         utils,
       },
@@ -241,8 +242,8 @@ const makeThrowingMatcher = (
   };
 };
 
-expect.extend = (matchersObj: MatchersObject): void => {
-  Object.assign(global[GLOBAL_STATE].matchers, matchersObj);
+expect.extend = (matchers: MatchersObject): void => {
+  Object.assign(global[GLOBAL_STATE].matchers, matchers);
 };
 
 expect.anything = anything;

types/Matchers.js

@@ -25,17 +25,18 @@ export type RawMatcherFn = (
 
 export type ThrowingMatcherFn = (actual: any) => void;
 export type PromiseMatcherFn = (actual: any) => Promise<void>;
-export type MatcherContext = {isNot: boolean};
 export type MatcherState = {
   assertionCalls: number,
   currentTestName?: string,
+  equals: (any, any) => boolean,
   expand?: boolean,
   expectedAssertionsNumber: ?number,
   isExpectingAssertions: ?boolean,
   isNot: boolean,
   snapshotState: SnapshotState,
   suppressedErrors: Array<Error>,
   testPath?: Path,
+  utils: Object,
 };
 
 export type AsymmetricMatcher = Object;