Type error in webview's getMessageIdFromNode

[borisyankov]

Webview throws an exception: msgNode.getAttribute is not a function.

This happens both on Android and iOS (the only other known issue is Android-specific)

[gnprice]

Reported again yesterday, with a bit more detail. Screenshot:

This was on 15.0.92 (current latest), on iOS.

From a quick look at the code, this is in getMessageIdFromNode:

const getMessageIdFromNode = (node: Node): number => {
  const msgNode = getMessageNode(node);
  return msgNode ? +msgNode.getAttribute('data-msg-id') : -1;
};

So somehow we're getting a msgNode that is truthy, but doesn't have a getAttribute method.

[gnprice]

Oh also: asked what they were doing just before the error, the person who reported it says:

I just went to a stream and then a topic and I happened to tap the screen accidentally though I don’t think that would have anything to do with the error

Several call sites of getMessageIdFromNode are in our click event listener, so those are a likely suspect.

[chrisbobbe]

It looks like 65e3ea3 types node as ?Node instead of Node, but this wouldn't catch the problem Greg pointed out:

So somehow we're getting a msgNode that is truthy, but doesn't have a getAttribute method.

Also, getMessageIdFromNode was deprecated in 7f968e5, but it still has six call sites.

[gnprice]

Looking at Sentry events, we've had no cases of this in (at least) the past 90 days:
https://sentry.io/organizations/zulip/events/?project=191284&query=%22msgNode.getAttribute%22&statsPeriod=90d

To try to confirm that's not just a lack of data: the way these would get reported to Sentry is that the same window.onerror which puts up that red banner (or a less detailed one, in release builds) also posts an event through sendMessage, which gets processed here in webViewEventHandlers.js:

    case 'error':
      logging.error(`WebView exception: ${JSON.stringify(event.details)}`);
      break;

And we do get other exceptions reported through that path:
https://sentry.io/organizations/zulip/events/?project=191284&query=%22WebView+exception%22+%22TypeError%22&statsPeriod=14d

So it seems this got fixed at some point. 🤷‍♂️ If we hear a fresh report, we'll reopen.