react-native/packages/dev-middleware/src/__tests__/FetchUtils.js

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict-local
 * @format
 * @oncall react_native
 */

import type {JSONSerializable} from '../inspector-proxy/types';

import {Agent} from 'undici';

declare var globalThis: $FlowFixMe;

/**
 * A version of `fetch` that is usable with the HTTPS server created in
 * ServerUtils (which uses a self-signed certificate).
 */
export async function fetchLocal(
  url: string,
  options?: Partial<Parameters<typeof fetch>[1] & {dispatcher?: mixed}>,
): ReturnType<typeof fetch> {
  return await fetch(url, {
    ...options,
    // Node's native `fetch` comes from undici and supports the same options,
    // including `dispatcher` which we use to make it accept self-signed
    // certificates.
    dispatcher:
      options?.dispatcher ??
      new Agent({
        connect: {
          rejectUnauthorized: false,
        },
      }),
  });
}

export async function fetchJson<T: JSONSerializable>(url: string): Promise<T> {
  const response = await fetchLocal(url);
  if (!response.ok) {
    throw new Error(`HTTP ${response.status} ${response.statusText}`);
  }
  return response.json();
}

/**
 * Change the global fetch dispatcher to allow self-signed certificates.
 * This runs with Jest's `beforeAll` and `afterAll`, and restores the original dispatcher.
 */
export function withFetchSelfSignedCertsForAllTests() {
  const fetchOriginal = globalThis.fetch;
  const selfSignedCertDispatcher = new Agent({
    connect: {
      rejectUnauthorized: false,
    },
  });

  let fetchSpy;

  beforeAll(() => {
    // For some reason, setting the `selfSignedCertDispatcher` with `setGlobalDispatcher` doesn't work.
    // Instead of using `setGlobalDispatcher`, we'll use a spy to intercept the fetch calls and add the dispatcher.
    fetchSpy = jest
      .spyOn(globalThis, 'fetch')
      .mockImplementation((url, options) =>
        fetchOriginal(url, {
          ...options,
          dispatcher: options?.dispatcher ?? selfSignedCertDispatcher,
        }),
      );
  });

  afterAll(() => {
    fetchSpy.mockRestore();
  });
}