[Feature Request] Composing multiple default packages into a list

[albertfgu]

🚀 Feature Request

Motivation

Is your feature request related to a problem? Please describe.
I apologize if this feature exists or has been asked before, but I couldn't find a solution.

I have a Python class that accepts a list of configs. Imagine a number of configs for individual classes that can be instantiated:

configs/model/linear.yaml:

_target_: torch.nn.Linear
in_features: 10
out_features: 10

configs/model/relu.yaml:

_target_: torch.nn.ReLU

Now imagine wanting to create something like nn.Sequential flexibly from command line. In particular, I'd like to flexibly be able to create configs such as

configs/model/model1.yaml:

- _target_: torch.nn.Linear
  in_features: 10
  out_features: 10
- _target_: torch.nn.ReLU

configs/model/model2.yaml:

- _target_: torch.nn.Linear
  in_features: 10
  out_features: 10
- _target_: torch.nn.Linear
  in_features: 10
  out_features: 20

However, I don't want to create a config for every possible combination. An ideal interface would be something like
configs/model/model1.yaml:

defaults:
  - linear
  - relu

However, this clearly doesn't work and I'm not sure what other interface could make sense. Maybe an alternative interface could be
configs/model/model1.yaml:

defaults:
  - linear@0
  - relu@1

Any ideas for how to implement something like this?

[Jasha10]

See #1939, as well as the other issues tagged with the "list composition" tag. I'm going to close this issue in favor of #1939.

For a relatively cumbersome workaround, see my comments here and here.

[albertfgu]

Thanks for the reference!