flow.validate_parameters regression

[j-tr]

Bug summary

Certain flow deployments that worked fine before cannot be executed anymore after updating from Prefect 2.20.9 to any newer Prefect version.
This is due to a change in the parameter validation.

MRE:

from prefect import flow

@flow
def my_flow(param: dict[str, str]):
    pass

flow_run_params = {
    "param": {'foo': 'bar'}
}

my_flow.validate_parameters(flow_run_params)

runs fine for Prefect <= 2.20.9.

But raises

Traceback (most recent call last):
  File "mre.py", line 13, in <module>
    my_flow.validate_parameters(flow_run_params)
  File "mre.py", line 532, in validate_parameters
    has_v1_models = any(
  File "mre.py", line 533, in <genexpr>
    issubclass(param.annotation, V1BaseModel)
  File "/usr/lib/python3.10/abc.py", line 123, in __subclasscheck__
    return _abc_subclasscheck(cls, subclass)
TypeError: issubclass() arg 1 must be a class

for Prefect >= 2.20.10

Version info

Version:             2.20.14
API version:         0.8.4
Python version:      3.10.12
Git commit:          fb919c67
Built:               Mon, Nov 18, 2024 4:41 PM
OS/Arch:             linux/x86_64
Server type:         cloud

Additional context

related to #15608

[zzstoatzz]

hi @j-tr - thanks for the issue!

can you share what version of pydantic you are using? I cannot seem to directly reproduce this

In [1]: from prefect import flow
   ...:
   ...: @flow
   ...: def my_flow(param: dict[str, str]):
   ...:     pass
   ...:
   ...: flow_run_params = {
   ...:     "param": {'foo': 'bar'}
   ...: }
   ...:
   ...: my_flow.validate_parameters(flow_run_params)

Out[1]: {'param': {'foo': 'bar'}}

In [2]:

In [2]: !uv pip list | rg 'prefect|pydantic'
prefect                             2.20.14                           /Users/nate/github.com/prefecthq/prefect
pydantic                            2.10.2
pydantic-core                       2.27.1

---

EDIT: interesting, ok I reproduce it on python 3.10...

[zzstoatzz]

thanks @j-tr - this should be fixed by the above PR