<embed> does not handle network errors

[annevk]

The current set of steps seem to assume there's always a response.

[annevk]

<embed src=http://test:test/ onerror=w(1) onload=w(2)></embed> gives 2 in Chrome, nothing in Firefox...

[domenic]

Closed by 63a0e64 but GitHub isn't picking that up... there seems to be some general degraded GitHub status.

[laukstein]

@domenic, should we be able to identify trough JavaScript if iframe failed to load (is blocked by network or CSP)?

Currently with what I can came up is in onload event

const isLoaded = event.target.contentDocument ||
    event.target.contentWindow.window && event.target.contentWindow.window.length ||
    event.target.contentWindow.location && event.target.contentWindow.location.href;

but it will fail on Firefox due to issue https://bugzilla.mozilla.org/show_bug.cgi?id=1552504
Chrome will not fire onerror event (based on spec) https://bugs.chromium.org/p/chromium/issues/detail?id=365457

Is there any spec approach for it?

[laukstein]

@mfreed7 was it security concern to fire onload and not onerror when iframe failed to load by CSP or blocked network? Otherwise it should be considered as a bug in spec. cc @domenic @paulirish

[domenic]

It is intentional to align with 2/3 browsers here. Embed is a legacy element and we are working to simplify it as much as possible.

[laukstein]

@domenic, I am referring to <iframe> element.

I think Chrome Issue #365457, Issue #899559 and Issue #938279, and likely other browsers are missing this part

https://html.spec.whatwg.org/multipage/iframe-embed-object.html
If the load failed (e.g. there was an HTTP 404 error, there was a DNS error), fire an event named error at the element, then jump to the step below labeled fallback.

Chrome doesn't fire error event and instead fires load event when iframe load failed by CSP or other reason.

[domenic]

Yes, that's per spec, and also unrelated to this issue, so this is not a good place to discuss it.

[laukstein]

@domenic, can you please collaborate in https://bugs.chromium.org/p/chromium/issues/detail?id=899559#c9 and make clear the iframe error spec? I think there has been some misunderstanding.