Add expect.anything() (denoland#3964)

WIP

expect/_anything_test.ts

@@ -0,0 +1,20 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+import { expect } from "./expect.ts";
+import { AssertionError, assertThrows } from "../assert/mod.ts";
+
+Deno.test("expect().anything()", () => {
+  expect(null).not.toEqual(expect.anything())
+  expect(undefined).not.toEqual(expect.anything())
+  expect(1).toEqual(expect.anything())
+
+  assertThrows(() => {
+    expect(null).toEqual(expect.anything())
+  }, AssertionError);
+  assertThrows(() => {
+    expect(undefined).toEqual(expect.anything())
+  }, AssertionError);
+  assertThrows(() => {
+    expect(1).not.toEqual(expect.anything())
+  }, AssertionError);
+});

expect/_asymetric_matchers.ts

@@ -0,0 +1,9 @@
+export class Anything {
+  equals(other: unknown): boolean {
+    return other !== null && other !== undefined;
+  }
+}
+
+export function generateAnything(): Anything {
+  return new Anything();
+}

expect/_equal.ts

@@ -3,6 +3,7 @@
 // This file is copied from `std/assert`.
 
 import { EqualOptions } from "./_types.ts";
+import { Anything } from "./_asymetric_matchers.ts";
 
 function isKeyedCollection(x: unknown): x is Set<unknown> {
   return [Symbol.iterator, "size"].every((k) => k in (x as Set<unknown>));
@@ -52,6 +53,9 @@ export function equal(c: unknown, d: unknown, options?: EqualOptions): boolean {
     ) {
       return String(a) === String(b);
     }
+    if (b instanceof Anything) {
+      return (b as Anything).equals(a);
+    }
     if (a instanceof Date && b instanceof Date) {
       const aTime = a.getTime();
       const bTime = b.getTime();
@@ -95,7 +99,7 @@ export function equal(c: unknown, d: unknown, options?: EqualOptions): boolean {
       if (!strictCheck) {
         if (aLen > 0) {
           for (let i = 0; i < aKeys.length; i += 1) {
-            const key = aKeys[i];
+            const key = aKeys[i]!;
             if (
               (key in a) && (a[key as keyof typeof a] === undefined) &&
               !(key in b)
@@ -107,7 +111,7 @@ export function equal(c: unknown, d: unknown, options?: EqualOptions): boolean {
 
         if (bLen > 0) {
           for (let i = 0; i < bKeys.length; i += 1) {
-            const key = bKeys[i];
+            const key = bKeys[i]!;
             if (
               (key in b) && (b[key as keyof typeof b] === undefined) &&
               !(key in a)

expect/expect.ts

@@ -47,6 +47,7 @@ import {
   toThrow,
 } from "./_matchers.ts";
 import { isPromiseLike } from "./_utils.ts";
+import {generateAnything} from "./_asymetric_matchers.ts";
 
 const matchers: Record<MatcherKey, Matcher> = {
   lastCalledWith: toHaveBeenLastCalledWith,
@@ -168,3 +169,4 @@ export function expect(value: unknown, customMessage?: string): Expected {
 }
 
 expect.addEqualityTesters = addCustomEqualityTesters;
+expect.anything = generateAnything;