[Feature Request] Self-referencing _target_

[Laleee]

🚀 Feature Request

Defining default value for target which will refer to the same class.

Motivation

I have a lot of classes whose target is self. It would be fantastic if target could have some keyword that could suggest that the target is that same class.

Pitch

@dataclass
class SomeDataClass:
    attr1: str
    attr2: str
    att3: int
    _target_: str = 'path.to.the.file.SomeDataClas'

Additional context

I guess it's possible to automatically extract the class path relative to the project's root.

[Jasha10]

I think you can get away with using the module's __name__ attribute for this:

@dataclass
class SomeDataClass:
    attr1: str
    attr2: str
    att3: int
    _target_: str = __name__ + ".SomeDataClass"

or even:

@dataclass
class SomeDataClass:
    attr1: str
    attr2: str
    att3: int
    _target_: str = f"{__name__}.{__qualname__}"  # path to Self

An alternative would be to skip defining the _target_ field and use OmegaConf.to_object:

from dataclasses import dataclass
from omegaconf import OmegaConf

@dataclass
class SomeDataClass:
    attr1: str
    attr2: str
    att3: int

cfg = OmegaConf.create(SomeDataClass("foo", "bar", 123))

instance = OmegaConf.to_object(cfg)
assert isinstance(instance, SomeDataClass)
assert instance.attr1 == "foo"

See issue #1719 for caveats regarding the combination of hydra.utils.instantiate with OmegaConf.to_object.

[Laleee]

The second solution is great! Thanks a lot Jasha!

I think that 3. solution woudn't work when attributes are more complex (I'd have to mess with OmegaConfig's allow_objects).