Working with nested Outputs

[crabhi]

Hi everyone,
after I create a stack, I need to generate a custom config file. For this, I need to access some outputs, such as my_list_of_ec2_instances[i].public_ip.

I haven't found a good way to wait for all nested outputs to be available and then access them. Especially because I have a nested structure of objects. So far, the best way seems to use Output.json_dumps:

my_config = { 
   ...   # using lifted outputs from the generated objects
}
Output.json_dumps(my_config).apply(lambda x: json.loads(x)).apply(something_something)

Is there a way to do the above without the JSON trip?

[Frassle]

The typing information is sub-optimal for this operation but if you just call Output.from_input(my_config) it will collapse output values to plain values recursively.

[crabhi]

Works like a charm, thanks!

I didn't get it from the docs that this function can transform a (potentially nested) Dict[str, Output[T]] into Output[Dict[str, T]].

[crabhi]

By the way, why is json_dumps needed then? Couldn't it be implemented as Output.from_input(data).apply(json.dumps)?

[Frassle]

from_input only recurses through known types (tuples, lists, dictionaries, etc) so if you have a custom type with Output attributes on it from_input won't change those. It could be surprising if you had a class explicitly with an Output value on it which would get made into a plain value if it got passed through from_input.
json_dumps will handle nested Output values even in custom types, this is safe because the final result is just a JSON string.

[crabhi]

Interesting, thank you!