ScheduleInterval schema in OpenAPI specs should have "nullable: true" otherwise generated OpenAPI client will throw an error in case of nullable "schedule_interval"

Apache Airflow version

2.2.4 (latest released)

What happened

Currently we have this schema definition in the OpenAPI specs:

    ScheduleInterval:
      description: |
        Schedule interval. Defines how often DAG runs, this object gets added to your latest task instance's
        execution_date to figure out the next schedule.
      readOnly: true
      oneOf:
        - $ref: '#/components/schemas/TimeDelta'
        - $ref: '#/components/schemas/RelativeDelta'
        - $ref: '#/components/schemas/CronExpression'
      discriminator:
        propertyName: __type

The issue with above is, when using an OpenAPI generator for Java for example (I think is same for other languages as well), it will treat ScheduleInterval as non-nullable property, although what is returned under /dags/{dag_id} or /dags/{dag_id}/details in case of a None schedule_interval is null for schedule_interval.

What you think should happen instead

We should have nullable: true in ScheduleInterval schema which will allow schedule_interval to be parsed as null.

How to reproduce

No response

Operating System

Linux

Versions of Apache Airflow Providers

No response

Deployment

Official Apache Airflow Helm Chart

Deployment details

No response

Anything else

If the maintainers think is a valid bug, I will be more than happy to submit a PR 😃

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

[uranusjr]

From what I understand, the problem is not in the API response, but the generated API clients. The response you have above is currently not consumable by an API client. Adding nullable: true would allow the clients to handle "schedule_interval": null correctly. The generated API clients are not a part of the main Airflow repository, but they do rely on the openapi/v1.yml file in here, so we need to fix it for them.

[uranusjr]

Good catch. Pull request would be very welcomed!