When I tried to implement MozNFCPeerEvent for NFC in Bug 1046554, I'd like to make the 'peer' property non-nullable, however met compilation error in [1], and the reason for why this 'peer' shouldn't be nullable is this event (MozNFCPeerEvent) is fired when another MozNFCPeer is detected, so the 'peer' should be a valid MozNFCPeer object, and shouldn't be null. Also W3C NFC API has defined this NFCPeerEvent with non-nullable 'peer' property, see [2]. After consulting smaug, he said we should file a bug for this. [1]: https://bugzilla.mozilla.org/show_bug.cgi?id=1046554#c4 [2]: http://w3c.github.io/nfc/proposals/common/nfc.html#nfcpeerevent-interface

The W3C API as written doesn't seem to me like it would pass TAG review: it has no constructor for the event... Given that we _do_ apparently want to have a constructor, what is its expected behavior when the passed-in dictionary doesn't have a "peer" property?

I meant you should file a spec bug about this, sorry about not being clear about.