Cannot use TypedDict object when defining params

[jcobb-healx]

Apache Airflow version

2.5.1

What happened

Context: I am attempting to use TypedDict objects to maintain the keys used in DAG params in a single place, and check for key names across multiple DAGs that use the params.
This raises an error with mypy as params expects an Optional[Dict]. Due to the invariance of Dict, this does not accept TypedDict objects.

What happened: I passed a TypedDict to the params arg of DAG and got a TypeError.

What you think should happen instead

TypedDict objects should be accepted by DAG, which should accept Optional[Mapping[str, Any]].

Unless I'm mistaken, params are converted to a ParamsDict class and therefore the appropriate type hint is a generic Mapping type.

How to reproduce

Steps to reproduce

from typing import TypedDict

from airflow import DAG
from airflow.models import Param

class ParamsTypedDict(TypedDict):
    str_param: Param

params: ParamsTypedDict = {
    "str_param": Param("", type="str")
}

with DAG(
    dag_id="mypy-error-dag",
    # The line below raises a mypy error
    # Argument "params" to "DAG" has incompatible type "ParamsTypedDict"; expected "Optional[Dict[Any, Any]]"  [arg-type]
    params=params,  
) as dag:
    pass

Operating System

Amazon Linux

Versions of Apache Airflow Providers

No response

Deployment

Docker-Compose

Deployment details

No response

Anything else

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

[boring-cyborg]

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[jcobb-healx]

Relevant mypy discussion on passing TypedDict as args annotated with Dict: python/mypy#4976

[potiuk]

Feel free to work on it.

[pierrejeambrun]

@jcobb-healx Are you still working on this ? Don't hesitate to reach out if you need some help :)

[jcobb-healx]

@pierrejeambrun Sorry, I hadn't gotten around to looking at this. Spent a bit of time on this today, and it looks like converting the type hint to Mapping isn't right, as the params are merged with the default params in an update call, which isn't consistent with TypedDict behaviour.
Given the earlier mypy discussion, it probably makes sense to use MutableMapping to allow generic inputs, and let users perform casts, i.e. not accept TypedDict objects.

[jcobb-healx]

@pierrejeambrun I've made the changes to use MutableMapping so that passing in a ParamsDict object works as expected. I've not changed anything that would allow my original case to work, so I've made no mention of TypedDict in the PR