expo/src/winter/runtime.native.ts

The Expo SDK

// This file configures the runtime environment to increase compatibility with WinterCG.
// https://wintercg.org/

import '../../types';

import { installAbortSignalPatch } from './AbortSignal';
import { installFormDataPatch } from './FormData';
import { installGlobal as install } from './installGlobal';

// https://encoding.spec.whatwg.org/#textdecoder
install('TextDecoder', () => require('./TextDecoder').TextDecoder);
// https://encoding.spec.whatwg.org/#interface-textdecoderstream
install('TextDecoderStream', () => require('./TextDecoderStream').TextDecoderStream);
// https://encoding.spec.whatwg.org/#interface-textencoderstream
install('TextEncoderStream', () => require('./TextDecoderStream').TextEncoderStream);
// https://url.spec.whatwg.org/#url
install('URL', () => require('./url').URL);
// https://url.spec.whatwg.org/#urlsearchparams
install('URLSearchParams', () => require('./url').URLSearchParams);
// https://webidl.spec.whatwg.org/#idl-DOMException
install('DOMException', () => require('./DOMException').DOMException);
// https://streams.spec.whatwg.org/#rs
// ReadableStream is injected by Metro as a global

install('__ExpoImportMetaRegistry', () => require('./ImportMetaRegistry').ImportMetaRegistry);

// https://html.spec.whatwg.org/multipage/structured-data.html#structuredclone
install('structuredClone', () => require('@ungap/structured-clone').default);

installFormDataPatch(FormData);
installAbortSignalPatch(AbortSignal);

// Polyfill async iterator symbol for Hermes.
// @ts-expect-error: readonly property only applies when the engine supports it
Symbol.asyncIterator ??= Symbol.for('Symbol.asyncIterator');

const useRnFetch =
  process.env.EXPO_PUBLIC_USE_RN_FETCH === '1' || process.env.EXPO_PUBLIC_USE_RN_FETCH === 'true';

if (!useRnFetch) {
  // Reading `Headers` triggers RN's polyfill chain, which also installs
  // `Request` and `Response`. Must run before we replace `fetch` below.
  if (!globalThis.Headers) {
    throw new Error(
      "expo/fetch expected `globalThis.Headers` to be installed by React Native's fetch polyfill."
    );
  }
  install('fetch', () => require('./fetch').fetch);
}