What are you really trying to do?

Note: this issue came about because we implemented our own from_payload from scratch. I just rewrote the code to reuse JSONPlainPayloadConverter and just define our own custom_type_converters instead of reimplementing the whole thing. So this doesn't affect us anymore, but it's still a confusing error to get

We're defining our own custom from_payload function that deserializes according to the type_hint. If the type_hint isn't supported, we throw an error like

raise ValueError(f"{val} does not match {type_hint}")

When using a dataclass with a datetime field, this errors with

TypeError: descriptor '__format__' for 'datetime.date' objects doesn't apply to a 'str' object

Related: #301

Describe the bug

Normally, running

from datetime import datetime
format(datetime, "")

will desugar as type(datetime).__format__(datetime, ""), where type(datetime) is type and type.__format__ just calls str().

But when datetime is a _RestrictedProxy, format(proxy_datetime, "") will run _RestrictedProxy.__format__(proxy_datetime, ""), which will run real_datetime.__format__(""), which throws the above error.

Current workaround is to explicitly convert to str like f"{type_hint!s}", but the error is very confusing

Minimal Reproduction

Environment/Versions

• OS and processor: [e.g. M1 Mac, x86 Windows, Linux]
• Temporal Version: [e.g. 1.14.0?] and/or SDK version
• Are you using Docker or Kubernetes or building Temporal from source?

Additional context