Description

XComArg is a class that references an XCom entry from an operator. Can be used to explicitly set XCom dependencies and explictly pass results between operators.

Class attributes:

• operator: BaseOperator: Origin operator instance.
• key: str: Stores key for XCom value. Defaults to airflow.models.xcom. XCOM_RETURN_KEY

Class methods

• get(context: dict)-> Any: Resolves XCom value given operator and key.
• __getitem__(key, str) -> XComArg: Easy method to create new XComArg using the same operator but a different key.
• add_downstream_dependent(operator: BaseOperator)->None: Add an operator as a downstream dependency of operator. [Optional] Makes this task simpler.

Proposed implementation: https://github.com/casassg/corrent/blob/master/corrent/xcom_arg.py

Use case / motivation

• Explicit way to pass around results between operators.
• This object is a reference to an XCom value that has not been created and will need to be resolved in the future.
• It can generate new XComArgs that point to the same operator but has a different key by using the key accessor. E.g: output['train'].
• To do so, it includes as class attributes both the originating operator instance and a key (both needed to pull the XCom).
• Has a property op that allows access to the origin operator.

Stretch goal

• Store type class for the XCom and lie to MyPy when trying to check class signature.