AttributeError when using dataclass with schema function

[JayH5]

Bug

Please complete:

• OS: macOS
• Python version import sys; print(sys.version): 3.7.4
• Pydantic version import pydantic; print(pydantic.VERSION): 0.32.2, as well as master as of 7901711

Where possible please include a self contained code snippet describing your bug:

from pydantic.dataclasses import dataclass
from pydantic.schema import schema

@dataclass
class Model:
    name: str

schema([Model])

This produces an error message like:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/jamie/.virtualenvs/tempenv-74cd74727d61/lib/python3.7/site-packages/pydantic/schema.py", line 185, in schema
    flat_models = get_flat_models_from_models(models)
  File "/Users/jamie/.virtualenvs/tempenv-74cd74727d61/lib/python3.7/site-packages/pydantic/schema.py", line 437, in get_flat_models_from_models
    flat_models |= get_flat_models_from_model(model)
  File "/Users/jamie/.virtualenvs/tempenv-74cd74727d61/lib/python3.7/site-packages/pydantic/schema.py", line 378, in get_flat_models_from_model
    fields = cast(Sequence[Field], model.__fields__.values())
AttributeError: type object 'Model' has no attribute '__fields__'

The same code using BaseModel instead of the @dataclass works fine.

With the dataclass, Model.__pydantic_model__.schema() also works.

[samuelcolvin]

That's not how the schema function is designed to work. Did you find somewhere in the docs that suggested that?

For now the solution is to use Model.__pydantic_model__.schema(), if you'd like to modify schema() to accept a dataclass, please submit a PR.

[JayH5]

That's not how the schema function is designed to work. Did you find somewhere in the docs that suggested that?

Ah, apologies, I must've misunderstood. I mostly just expected dataclasses to work similarly to things that inherit from BaseModel and don't think I read that schema() supports them.

I'd like to make a PR but honestly I'm not sure when I will have the time, so feel free to close if you want.

[samuelcolvin]

no problem. Would definitely be better if schema() worked with dataclasses as it does with models, so I'll leave this open and fix it when I get a chance if no one else does before.