Referencing a resource in another resource group

[JustinGrote]

Wasn't sure to file this as an issue or if I'm just doing it wrong.

I have a template where the user can supply a Microsoft.Compute/sshPublicKeys@2020-06-01 resource id to configure the SSH key on the system. I want the key to be referenceable anywhere, not just in the same resource group, because I just get the publickey property string and populate it as part of userdata on a compute node. (I can't use the typical method because Fortigates are dumb)

Typically in ARM I do it like this and it works fine:
var publicKey = reference(AdminSshPublicKeyId,'2020-06-01').publicKey

Where AdminSshPublicKeyId is the full resourceId (/subscriptions/xxx/etc.)

How can I do it the Bicep way using existing to get a symbolic handle? I tried something like this

resource fortigateSSHKey 'Microsoft.Compute/sshPublicKeys@2020-06-01' existing = if (!empty(AdminSshPublicKeyId)) {
  name: AdminSshPublicKeyId
  scope: subscription()
}

But got an error saying I could only use resourceGroup scope, and couldn't figure out any combination to make it work for a resource not in the same resource group.

[JustinGrote]

I got it to work with scope: resourceGroup('TheThingsResourceGroup') but then I have to parse that out of the ID etc which is more boilerplate than just doing the reference so wondering if I missed something.

[brwilkinson]

is this resolved now via:

fortigateSSHKey.id ?

[brwilkinson]

@JustinGrote I am just making sure discussions are getting attended to. Figured I would ping you, to ask if you would mind marking this one as "answered"?

[alex-frankel]

Just adding a note here for housekeeping that this will be solved by #1722