boolean flow parameter defaults to False in UI when no default is given in code about prefect HOT 2 OPEN

Note that the suggested workaround of clicking omit value on the optional parameter is not viable in our case. Accidentally sending the (unwanted) default value False could have huge consequences. For now we work around this by explicitly using the default value True but we'd rather have an explicitly optional value.

Another suggestion was to use a dropdown, maybe something. like Literal['true', 'false'] | None. However, that would require a redundant pydantic BaseModel for the UI vs internal representation.

from prefect.

hello @martin-schulze-e2m - I can reproduce this only with pydantic<2

from prefect import flow


@flow(log_prints=True)
def optional_bool(x: bool | None = None) -> bool:
    print(x)


if __name__ == "__main__":
    optional_bool.serve("optional-bool")

with pydantic==1.x

» prefect deployment inspect optional-bool/optional-bool

{
  "parameter_openapi_schema": {
    "type": "object",
    "title": "Parameters",
    "properties": {
      "x": {
        "type": "boolean",
        "title": "x",
        "position": 0
      }
    }
  }
}

with pydantic 2.x

{
  "parameter_openapi_schema": {
    "type": "object",
    "title": "Parameters",
    "properties": {
      "x": {
        "anyOf": [
          {
            "type": "boolean"
          },
          {
            "type": "null"
          }
        ],
        "title": "x",
        "default": null,
        "position": 0
      }
    }
}

a bool toggle seems like the correct thing for the UI to render in the case of the OpenAPI schema resulting from the pydantic 1 case. It seems like this is a limitation of the way pydantic 1 dumps Optional types into an OpenAPI schema.

if you're stuck on pydantic 1, how is this for a workaround?

from pydantic import BaseModel

from prefect import flow


class noop(BaseModel):
    """A class that does nothing"""


@flow(log_prints=True)
def optional_bool(x: bool | noop = noop()):
    print(x)


if __name__ == "__main__":
    optional_bool.serve("optional-bool")

from prefect.