import { isNativeFetch, logger } from '@sentry/utils'; import { DEBUG_BUILD } from '../debug-build.js'; import { WINDOW } from '../helpers.js'; let cachedFetchImpl = undefined; /** * A special usecase for incorrectly wrapped Fetch APIs in conjunction with ad-blockers. * Whenever someone wraps the Fetch API and returns the wrong promise chain, * this chain becomes orphaned and there is no possible way to capture it's rejections * other than allowing it bubble up to this very handler. eg. * * const f = window.fetch; * window.fetch = function () { * const p = f.apply(this, arguments); * * p.then(function() { * console.log('hi.'); * }); * * return p; * } * * `p.then(function () { ... })` is producing a completely separate promise chain, * however, what's returned is `p` - the result of original `fetch` call. * * This mean, that whenever we use the Fetch API to send our own requests, _and_ * some ad-blocker blocks it, this orphaned chain will _always_ reject, * effectively causing another event to be captured. * This makes a whole process become an infinite loop, which we need to somehow * deal with, and break it in one way or another. * * To deal with this issue, we are making sure that we _always_ use the real * browser Fetch API, instead of relying on what `window.fetch` exposes. * The only downside to this would be missing our own requests as breadcrumbs, * but because we are already not doing this, it should be just fine. * * Possible failed fetch error messages per-browser: * * Chrome: Failed to fetch * Edge: Failed to Fetch * Firefox: NetworkError when attempting to fetch resource * Safari: resource blocked by content blocker */ function getNativeFetchImplementation() { if (cachedFetchImpl) { return cachedFetchImpl; } /* eslint-disable @typescript-eslint/unbound-method */ // Fast path to avoid DOM I/O if (isNativeFetch(WINDOW.fetch)) { return (cachedFetchImpl = WINDOW.fetch.bind(WINDOW)); } const document = WINDOW.document; let fetchImpl = WINDOW.fetch; // eslint-disable-next-line deprecation/deprecation if (document && typeof document.createElement === 'function') { try { const sandbox = document.createElement('iframe'); sandbox.hidden = true; document.head.appendChild(sandbox); const contentWindow = sandbox.contentWindow; if (contentWindow && contentWindow.fetch) { fetchImpl = contentWindow.fetch; } document.head.removeChild(sandbox); } catch (e) { DEBUG_BUILD && logger.warn('Could not create sandbox iframe for pure fetch check, bailing to window.fetch: ', e); } } return (cachedFetchImpl = fetchImpl.bind(WINDOW)); /* eslint-enable @typescript-eslint/unbound-method */ } /** Clears cached fetch impl */ function clearCachedFetchImplementation() { cachedFetchImpl = undefined; } export { clearCachedFetchImplementation, getNativeFetchImplementation }; //# sourceMappingURL=utils.js.map