What is the exception contract for the .NET Google.Cloud.Firestore API?

Google's .NET Firestore library documents its API, but leaves out any information about its exception behaviour.

Is there any reference for what "line of business" exceptions can be thrown by the API? For example,

• if I await FirestoreDbBuilder.BuildAsync() without valid authentication available
• if I await FirestoreDbBuilder.BuildAsync() without network available
• if the network is down when I await CollectionReference.GetSnapshotAsync()
• if the network goes down while listening to CollectionReference.Listen(Action<QuerySnapshot>, CancellationToken)

I'm not especially concerned by "malformed executable" exceptions, like what happens if someone deletes the library DLLs.

No, I'm afraid there's no policy document for this.

In general though:

• When making gRPC calls (like GetSnapshotAsync does) I'd expect an RpcException to be thrown
• When calling BuildAsync, it very much depends on the credentials:
  • When using default credentials, if the credentials are present in the
    form of a JSON file, no network is needed but InvalidOperationException will be thrown if the file is invalid JSON or does not represent valid credential parameters
  • If the credentials are passed directly, just calling BuildAsync doesn't do anything with the credentials immediately

Additionally, if you don't specify the project ID in the builder, BuildAsync will need to ascertain that automatically - which ends up throwing ArgumentNullException when constructing the actual FirestoreDb. (That's possibly not ideal; I can see us potentially changing that to InvalidOperationException in a later version - probably in a major version bump though.)