Incorrect signature of operators

Hello,

Currently, the signatures of most operators look similar to the following.

    @apply_defaults
    def __init__(
        self, sql: str, conn_id: Optional[str] = None, *args, **kwargs
    ) -> None:
        super().__init__(*args, **kwargs)
        self.conn_id = conn_id
        self.sql = sql

There are two problems here.

1. The apply_default decorator forces all arguments to be passed as keyword arguments, but this information is not marked in the signature. As of Python 3 it is possible to mark arguments as keyword-only argument.
2. The *args is passed to the BaseOperator class, but this class does not accept positional arguments.

The new operator signature may look like folllow

    @apply_defaults
    def __init__(
        self, *, sql: str, conn_id: Optional[str] = None, **kwargs
    ) -> None:
        super().__init__(**kwargs)
        self.conn_id = conn_id
        self.sql = sql

This change will allow the detection of improper operator initialization by static code analysis tools. This will also improve the operator’s documentation as the method signature is available in the Python API Reference.

This change is backward-compatible because the positional arguments were not accepted before, but this was not enforced by the Python interpreter, but by an ddecorator.

We can use Bowler to do it.

Best regards, Kamil

[mik-laj]

@LeonY1 CLA is not required.

[mik-laj]

@LeonY1 You can start. You are already assigned to this ticket so I cannot assign you again.