Add await method about issue#7407

[zorori777]

Problem

issue

Analysis

When I updated this pakcage from 10.0.0 to 10.1.0, suddenly happened this error.
So I checked each differences in change log between 10.0.0 to 10.1.0.
ChangeLog

Reason

#7351
It shouldn't remove await method.

This pull request's approval comments say There’s some async stuff happening in the constructor, in the fact constructor call async method. so it need to use await function.

According to error message, when synchronous processing finished, closed entire process at the same time.
Need to wait for asynchronous processing, so I add await method.

Fix

I add await method, removed it by #7351

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[simonhaenisch]

Not sure whether you've looked into the source code but this._targets is a map of Target instances. The assignment happens here:

puppeteer/src/common/Browser.ts

Lines 350 to 361 in 44b22bb

	const target = new Target(
	targetInfo,
	context,
	() => this._connection.createSession(targetInfo),
	this._ignoreHTTPSErrors,
	this._defaultViewport
	);
	assert(
	!this._targets.has(event.targetInfo.targetId),
	'Target should not exist before targetCreated'
	);
	this._targets.set(event.targetInfo.targetId, target);

The target's constructor might be doing some async work, but you can't mark a constructor as async and await the class instantiation (i. e. await new Target(...) is not possible). The instance will be immediately returned and the constructor's async work happens afterwards in the background.

Did you actually try building puppeteer with this change to see whether this fixes the issue for you?

---

Edit: the only thing I could imagine is that adding the await would defer this line to be executed later (i. e. pushes it to the end of the event loop). I just did a search and it seems like that's how it works according to this SO answer ("if you await things you will always defer the continuation to a microtask"). TIL 🤓

@mathiasbynens referring to #7351 (comment), is it possible that the await deferring did actually have an effect?

[jschfflr]

I feel like this patch might not really be fixing the problem because the next line is already awaiting target._initializedPromise. The original problem is probably timing related and therefore flaky.
Could you verify that this change is actually fixing the problem?

[jschfflr]

@zorori777 I'll close this for now as there hasn't been an update on this issue. Feel free to reopen if you think this is still relevant!