[Bug] Schema validation for recursively instantiated targets failing

[classner]

🐛 Bug

Description

I would like Hydra to instantiate a nested target which comes from interpolation with schema validation (following the example from #1420). Example:

config_test.yaml

defaults:
  - config_test_schema
  - _self_

child:
  _target_: config_test.Child
parent:
  _target_: config_test.Parent
  child: ${child}

config_test.py

import hydra
from hydra.utils import instantiate
from dataclasses import dataclass
from hydra.core.config_store import ConfigStore


@dataclass
class ConfigChild:
    _target_: str = "Child"


@dataclass
class ConfigParent:
    _target_: str = "Parent"
    child: ConfigChild = ConfigChild()


@dataclass
class TestConfig:
    child: ConfigChild = ConfigChild()
    parent: ConfigParent = ConfigParent()


cs = ConfigStore.instance()
cs.store(name="config_test_schema", node=TestConfig)


class Child:
    pass


class Parent:
    def __init__(self, child):
        self.child = child


@hydra.main(config_path=".", version_base=None, config_name="config_test")
def run(cfg):
    parent = instantiate(cfg.parent)
    print(parent.child)


if __name__ == "__main__":
    run()

This runs successfully if I remove the line - config_test_schema from the defaults in config_test.yaml. However, once the line is there running fails with

In 'config_test': ValidationError raised while composing config:
Merge error: str is not a subclass of ConfigChild. value: ${child}
    full_key: 
    object_type=TestConfig

Set the environment variable HYDRA_FULL_ERROR=1 for a complete stack trace.

Checklist

• I checked on the latest version of Hydra
• I created a minimal repro (See this for tips).

Expected Behavior

Instantiation of parent and child successful.

System information

• Hydra Version : 1.3.1
• Python version : 3.8.1
• Virtual environment type and version : venv 2.3.12
• Operating system : Linux

[jnzhnd]

Hey all, is there any update on this? I'm currently running into the same issue. My current workaround is to instantiate the schema and resolve the config, and then merging them to see if the config is valid. Is there a better solution?

resolved_config = OmegaConf.create(OmegaConf.to_container(my_config, resolve=True))
schema = OmegaConf.structured(MyConfigSchema)

OmegaConf.merge(schema, resolved_config)

[omry]

Closing this as an upstream OmegaConf structured-config merge issue. The minimal failure reproduces with pure OmegaConf by merging an interpolation into a structured-config field; Hydra is not required to trigger it.

This is tracked upstream in OmegaConf here: omry/omegaconf#1020