[BUG][PYTHON] should only allow timezone-aware datetime

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• [] Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

As described in https://github.com/OAI/OpenAPI-Specification/issues/1498#issuecomment-369680369, OpenAPI date-time strings must contain time-zone information.

In the Python client generator, the Pydantic fields are annotated with datetime, which allows timezone-naive objects to be passed. When serialized to strings, these do not contain time-zone information like a trailing Z or +00:00. This violates the OpenAPI spec.

openapi-generator version

7.7.0

OpenAPI declaration file content or url

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

I would change the type annotations for date-time format string to pydantic.types.AwareDatetime, to require the time-zone information that the OpenAPI spec asks for when objects are constructed in Python.

This can be a breaking change to users using lenient REST APIs with the generated client. It might also be annoying if server responses contain "incorrect" timezone-naive timestamps and client-side validation fails.

Looking forward to feedback on how this should be best handled, to correctly represent the OpenAPI spec but not be annoying to users.

The issue names no source file or test. Start by generating a Python client with version 7.7.0 and checking how its Pydantic date-time fields handle naive and timezone-aware values; done means the generated client enforces timezone information consistently with the OpenAPI date-time requirement, with the compatibility impact resolved.