Overriding configuration using an environment doesn't trigger type checks when merging into Structured config

[SimonStJG]

Describe the bug

If I create a structured configuration with an integer field and then merge in a configuration where that fields value is taken from an environment variable, the type checks usually associated with the structured field are not triggered.

To Reproduce

def test_strange_overriding_behaviour():
    @dataclass
    class Base:
        foo: int = omegaconf.MISSING

    override = textwrap.dedent("""
        foo: ${env:FOO_OVERRIDE}
    """)

    with MonkeyPatch.context() as mp:
        mp.setenv("FOO_OVERRIDE", "This is not an integer")
        base_conf = omegaconf.OmegaConf.structured(Base)
        override_conf = omegaconf.OmegaConf.create(override)

        # This does not raise ValidationError but merges successfully, and merged_conf.foo is set to the string
        # "This is not an integer"
        with pytest.raises(omegaconf.ValidationError):
            merged_conf = omegaconf.OmegaConf.merge(base_conf, override_conf)

Expected behavior

I expected a validation error to be raised on merge, as it would have been had I set:
override = "foo: "This is not an integer"

Additional context

• OmegaConf version: 2.0.5
• Python version: 3.8.5
• Operating system : Ubuntu 16.04.7 LTS
• Please provide a minimal repro

[SimonStJG]

Also tested on 2.0.6

[omry]

Custom resolvers return value is not merged into the config. They can actually return anything (including incompatible objects).

This behavior is intentional.
It's worth considering validating the return value of custom resolvers defined in typed fields, but that's an enhancement and not a bug.

[omry]

from dataclasses import dataclass
from omegaconf import SI, OmegaConf

OmegaConf.register_resolver("foo", lambda: "not an int")


@dataclass
class Foo:
    bar: int = SI("${foo:}")


foo = OmegaConf.structured(Foo)
print(foo.bar) # not an int

[SimonStJG]

Hi @omry, thanks for the explanation, that makes sense. Would you be interested in a little docs update pr, perhaps in the Interpolation subsection of the structured config section, to make this behaviour clear?

Also thanks for maintaining this, its been a lovely library to use.

[omry]

Yes, a PRs to improve the docs are always welcome!
Once we get into master, you can send a second PR cherry picking it into the 2.0_branch so that it appears in the docs for the current stable version.

Glad to hear you like OmegaConf. I also recommend that you check out Hydra, which builds on top of OmegaConf.

[odelalleau]

Reopening as this will be fixed by #445 an upcoming PR following up on #445 in OmegaConf 2.1.

The new behavior will automatically try to convert the output of a resolver (or any interpolation) into the desired type.