utils.js
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	import { getGlobalObject, isNativeFetch, logger, supportsFetch } from '@sentry/utils';

	var global = getGlobalObject();
	let cachedFetchImpl;

	/**
	* 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.
	*
	* var f = window.fetch;
	* window.fetch = function () {
	* var 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;
	}

	// Fast path to avoid DOM I/O
	if (isNativeFetch(global.fetch)) {
	return (cachedFetchImpl = global.fetch.bind(global));
	}

	var document = global.document;
	let fetchImpl = global.fetch;
	if (document && typeof document.createElement === 'function') {
	try {
	var sandbox = document.createElement('iframe');
	sandbox.hidden = true;
	document.head.appendChild(sandbox);
	var contentWindow = sandbox.contentWindow;
	if (contentWindow && contentWindow.fetch) {
	fetchImpl = contentWindow.fetch;
	}
	document.head.removeChild(sandbox);
	} catch (e) {
	(typeof __SENTRY_DEBUG__ === 'undefined' \|\| __SENTRY_DEBUG__) &&
	logger.warn('Could not create sandbox iframe for pure fetch check, bailing to window.fetch: ', e);
	}
	}

	return (cachedFetchImpl = fetchImpl.bind(global));
	}

	/**
	* Sends sdk client report using sendBeacon or fetch as a fallback if available
	*
	* @param url report endpoint
	* @param body report payload
	*/
	function sendReport(url, body) {
	var isRealNavigator = Object.prototype.toString.call(global && global.navigator) === '[object Navigator]';
	var hasSendBeacon = isRealNavigator && typeof global.navigator.sendBeacon === 'function';

	if (hasSendBeacon) {
	// Prevent illegal invocations - https://xgwang.me/posts/you-may-not-know-beacon/#it-may-throw-error%2C-be-sure-to-catch
	var sendBeacon = global.navigator.sendBeacon.bind(global.navigator);
	sendBeacon(url, body);
	} else if (supportsFetch()) {
	var fetch = getNativeFetchImplementation();
	fetch(url, {
	body,
	method: 'POST',
	credentials: 'omit',
	keepalive: true,
	}).then(null, error => {
	(typeof __SENTRY_DEBUG__ === 'undefined' \|\| __SENTRY_DEBUG__) && logger.error(error);
	});
	}
	}

	export { getNativeFetchImplementation, sendReport };
	//# sourceMappingURL=utils.js.map

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