Add EC2::Snapshot#wait_until_completed waiter

[amw]

It's currently possible to use Aws::EC2::Client.new.wait_until(:snapshot_completed, snapshot_ids: [snapshot.id]), I think it would be convenient to also be able to call snapshot.wait_until_completed.

[trevorrowe]

Thanks for the suggestion. This should be part of the next release.

[sandstrom]

Is this supposed to work?

irb(main):375:0> snapshot
=> #<struct Aws::EC2::Types::Snapshot data_encryption_key_id=nil, description="test snapshot, safe to del", encrypted=false, kms_key_id=nil, owner_id="773190852875", progress="", snapshot_id="snap-05a0bf6432567996a", start_time=2020-08-07 14:24:29 UTC, state="pending", state_message=nil, volume_id="vol-086363c9646c92e4a", volume_size=1, owner_alias=nil, tags=[]>

irb(main):376:0> snapshot.wait_until_completed
NoMethodError: undefined method `wait_until_completed' for #<Seahorse::Client::Response:0x000056256a69e8e0>

[alextwoods]

The Snapshot#wait_until_completed method is defined only for the Resource snapshot - it looks like you have the snapshot response from a Client call - its confusing and a weakness of the current way we do Resources (the object oriented model for interacting with services).

To use the Resource snapshot you can do something like:

resource = Aws::EC2::Resource.new(region: 'us-west-2')
snapshot = resource.create_snapshot(create_snapshot_opts) # this snapshot will now be an Aws::EC2::Snapshot object and NOT a Aws::EC2::Types::Snapshot
snapshot.wait_until_completed 

# Alternative
snapshot = Aws::EC2::Snapshot.new(id: snapshot_id)
snapshot.wait_until_completed

[sandstrom]

Alright, thanks for explaining!

After reading up on it this is mentioned in the readme/docs, though I must admit it wasn't super-obvious.

Perhaps you can use some method_missing trickery to display a more useful warning message in case the attempted method does not exist on the client call response, but does exist on the equivalent resource. That should be fairly easy to implement across all resources and would go a long way in usability.

Anyway, thanks for helping out @alextwoods! ⭐

[alextwoods]

Yeah - using method_missing is a good idea. I'll add that to our backlog - also happy to accept a PR for it!