[Don't review yet] Access hostname for app's

[shrshindeMSFT]

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[TrevorJoelHarris]

Looking at how this function is called in app.ts, it looks in some cases the app won't be initialized yet when you hit this line. Can I call like this actually work before the app is initialized? I think it wouldn't but maybe I'm forgetting/missing something. I think if there's no host to send it to the message will just sit forever and never receive a response.

If I assume that this won't work before initialize then I think this approach will have some problems. setWindows will not throw an error right now if the app is hosted in an iframe that isn't the hub-sdk for example.

I wonder if a slightly different approach could work. There are two different configurations TeamsJS can be in if the app that is using it is being hosted:

1. Frameless (app is hosted inside something like a webview)
2. Framed (app is hosted in an iframe).

For case 1, I think you could check if that one is the case relatively easily: if the current window is an ExtendedWindow that has nativeInterface defined on it, we can assume that the app is probably hosted by a host that is using a webview. Theoretically, someone that is not an official host could be running the app in a webview, but if they are it is unlikely that they have set up the WebView this way. See lines 104-107

For case 2 it is probably trickier. One thing you might be able to do is look at the domain that window.top is running at and then compare that domain to the list of validOrigins from the CDN. We may want to let the app developer pass in an additional set of "valid" host origins to check for in addition to the CDN list (the same list of valid origins they can pass to initialize).

If either of the cases above are true, we can tell the developer that they are probably being hosted by a host that will respond to their initialize call. We still might sometimes get it wrong, but in the worst case app developers will still be doing the same thing they are now: calling initialize and waiting for it to timeout.

What do you think?

[shrshindeMSFT]

Looking at how this function is called in app.ts, it looks in some cases the app won't be initialized yet when you hit this line. Can I call like this actually work before the app is initialized? I think it wouldn't but maybe I'm forgetting/missing something. I think if there's no host to send it to the message will just sit forever and never receive a response.

When the app is not hosted the set windows will throw error Initialization failed. ... and we can catch that error and tell the developer that app is not hosted. In app.ts we check if GlobalVars.isInitializeCompleted then use sendAndMessageToParentAsync as this will straight give the host name. For the second part where the app is not initialized setWindows sets the windows for communication and if it doesn't find any then it just throws error, if it finds the top window we send the message which will be handled by the hubSDK.