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std/assert/assert_rejects.ts

The Deno Standard Library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.import { AssertionError } from "./assertion_error.ts";import { assertIsError } from "./assert_is_error.ts";
/** * Executes a function which returns a promise, expecting it to reject. * * To assert that a synchronous function throws, use {@linkcode assertThrows}. * * @example * ```ts * import { assertRejects } from "https://deno.land/std@$STD_VERSION/assert/assert_rejects.ts"; * * await assertRejects(async () => Promise.reject(new Error())); // Doesn't throw * await assertRejects(async () => console.log("Hello world")); // Throws * ``` */export function assertRejects( fn: () => PromiseLike<unknown>, msg?: string,): Promise<unknown>;/** * Executes a function which returns a promise, expecting it to reject. * If it does not, then it throws. An error class and a string that should be * included in the error message can also be asserted. * * To assert that a synchronous function throws, use {@linkcode assertThrows}. * * @example * ```ts * import { assertRejects } from "https://deno.land/std@$STD_VERSION/assert/assert_rejects.ts"; * * await assertRejects(async () => Promise.reject(new Error()), Error); // Doesn't throw * await assertRejects(async () => Promise.reject(new Error()), SyntaxError); // Throws * ``` */export function assertRejects<E extends Error = Error>( fn: () => PromiseLike<unknown>, // deno-lint-ignore no-explicit-any ErrorClass: new (...args: any[]) => E, msgIncludes?: string, msg?: string,): Promise<E>;export async function assertRejects<E extends Error = Error>( fn: () => PromiseLike<unknown>, errorClassOrMsg?: // deno-lint-ignore no-explicit-any | (new (...args: any[]) => E) | string, msgIncludesOrMsg?: string, msg?: string,): Promise<E | Error | unknown> { // deno-lint-ignore no-explicit-any let ErrorClass: (new (...args: any[]) => E) | undefined = undefined; let msgIncludes: string | undefined = undefined; let err;
if (typeof errorClassOrMsg !== "string") { if ( errorClassOrMsg === undefined || errorClassOrMsg.prototype instanceof Error || errorClassOrMsg.prototype === Error.prototype ) { // deno-lint-ignore no-explicit-any ErrorClass = errorClassOrMsg as new (...args: any[]) => E; msgIncludes = msgIncludesOrMsg; } } else { msg = errorClassOrMsg; } let doesThrow = false; let isPromiseReturned = false; const msgSuffix = msg ? `: ${msg}` : "."; try { const possiblePromise = fn(); if ( possiblePromise && typeof possiblePromise === "object" && typeof possiblePromise.then === "function" ) { isPromiseReturned = true; await possiblePromise; } } catch (error) { if (!isPromiseReturned) { throw new AssertionError( `Function throws when expected to reject${msgSuffix}`, ); } if (ErrorClass) { if (error instanceof Error === false) { throw new AssertionError(`A non-Error object was rejected${msgSuffix}`); } assertIsError( error, ErrorClass, msgIncludes, msg, ); } err = error; doesThrow = true; } if (!doesThrow) { throw new AssertionError( `Expected function to reject${msgSuffix}`, ); } return err;}