Failed to create schema with optional fields

Just tried to use schema creation and it’s awesome, but I found, I think, bug with optional fields.

Here is my model:

from typing import Optional
from pydantic import BaseModel

class TestModel(BaseModel):
    foo: Optional[int] = None

print(TestModel.schema_json(indent=2))

Output:

Traceback (most recent call last):
  File "test_pydantic_schema.py", line 9, in <module>
    print(TestModel.schema_json(indent=2))
  File "/pydantic/pydantic/main.py", line 288, in schema_json
    return json.dumps(cls.schema(by_alias=by_alias), default=pydantic_encoder, **dumps_kwargs)
  File "/pydantic/pydantic/main.py", line 278, in schema
    s['properties'] = {f.alias: f.schema(by_alias) for f in cls.__fields__.values()}
  File "/pydantic/pydantic/main.py", line 278, in <dictcomp>
    s['properties'] = {f.alias: f.schema(by_alias) for f in cls.__fields__.values()}
  File "/pydantic/pydantic/fields.py", line 146, in schema
    if issubclass(self.type_, Enum):
TypeError: issubclass() arg 1 must be a class

Same issue with Union:

from typing import Union
from pydantic import BaseModel

class TestModel(BaseModel):
    foo: Union[str, int]

print(TestModel.schema_json(indent=2))

I think pydantic should cover cases like this, I don’t know what is the best way to solve issue with Optional, but in case of Union oneOf or anyOf rule can be used http://json-schema.org/latest/json-schema-validation.html#rfc.section.6.7.

[samuelcolvin]

as per discussion on gitter:

• the top level property should change type > schema
• there should be a shortened display of just 'schema': {'type': 'int'} which is just 'schema': 'int', this applies both at the top level for simple types and where simple types are nested within more complex types.

Overal the design is encapsulated by:

'foobar': {
  'schema': {
    'type': 'list',
    'item_type': {
      'mode': 'any_of',
      'types': [
        'float', 'int',
      ],
    }
  },
  'name': 'Foobar',
  'required': True,
}

[samuelcolvin]

ok, after looking at #218 I propose the following way to deal with this:

type becomes a dictionary.

For “simple” fields, eg. just an int or float, type like:

'type': {
  'item_type': 'float',
}

For unions we’d have:

'type': {
  'mode': 'any_of',
  'item_type': ['str', 'float'],
}

For things like List[int] we’d have:

'type': {
  'item_type': 'int',
  'shape': 'list',
}

or List[Union[int, str]] we’d have:

'type': {
  'mode': 'any_of',
  'item_type': ['int', 'str'],
  'shape': 'list',
}

For Dict[str, int] we’d have:

'type': {
  'item_type': 'int',
  'key_type': 'str',
  'shape': 'dict',
}

(we could add key_mode if the key is a union, but that’s a very rare case)

The names mode, item_type and shape are not great (suggestions very welcome), but I think this is the best way to go.

Questions:

• are their any case’s I’ve missed?
• do we do type: {'item_type': 'int', ...} or just add all these items to the main dict?
• what do we do when implement tuples #12, I guess something like properties on sub models?
• what do we do with Union[int, FoobarModel] - I guess we have type as above, then properties. What do we do with Union[FooModel, BarModel] - maybe this is just banned?

@Gr1N @x1ah