Prevent using dot in DAG name (?)

[airflowuser <ai...@protonmail.com.INVALID>]

Apparently dot - "." is a reserved char for sub-dags.
See here:  https://issues.apache.org/jira/browse/AIRFLOW-3292
I didn't know that, nor the author of this ticket (I assume others also don't know that as it isn't listed in the docs)
Reserve words/chars is something that is pretty fundamental.
Shouldn't Airflow prevent from users to use chars/words that may cause problems ?

Re: Prevent using dot in DAG name (?)

[y2...@gmail.com, y2...@gmail.com]

On 2019/01/27 12:54:18, airflowuser <ai...@protonmail.com.INVALID> wrote: 
> Apparently dot - "." is a reserved char for sub-dags.
> See here:  https://issues.apache.org/jira/browse/AIRFLOW-3292
> I didn't know that, nor the author of this ticket (I assume others also don't know that as it isn't listed in the docs)
> Reserve words/chars is something that is pretty fundamental.
> Shouldn't Airflow prevent from users to use chars/words that may cause problems ?

I've also been bitten by invalid characters thing [earlier](https://stackoverflow.com/a/51103180/3679900) (though mine was with task_id and not dag_id). I agree that this fine detail is missing in the docs and I had do do a fair bit of digging through to code to arrive at [airflow/utils/helpers.py](https://github.com/apache/airflow/blob/v1-10-stable/airflow/utils/helpers.py#L58)

Particularly regarding SubDags, the dot '.' character limitation seems inhibiting, and extending SubDagOperator to do away with [this check](https://github.com/apache/airflow/blob/v1-10-stable/airflow/operators/subdag_operator.py#L61) might have worked if it weren't for [this check](https://github.com/apache/airflow/blob/v1-10-stable/airflow/models.py#L3820), which isn't going away till Airflow 2.0

Also see [How to extend SubDagOperator?](https://stackoverflow.com/questions/42256675/)