Dataclass schema attr (#438)

fix #408

* Fix default field value compatibility for dataclass-based models

* Add unittests for dataclass schema bugfix

* Update HISTORY

HISTORY.rst

@@ -7,6 +7,7 @@ v0.21.1 (unreleased)
 ....................
 * add ``IPv{4,6,Any}Network`` and ``IPv{4,6,Any}Interface`` types from ``ipaddress`` stdlib, #333 by @pilosus
 * add docs for ``datetime`` types, #386 by @pilosus
+* fix to schema generation in dataclass-based models, #408 by @pilosus
 
 
 v0.21.0 (2019-03-15)

pydantic/dataclasses.py

@@ -3,6 +3,7 @@ from typing import TYPE_CHECKING, Any, Callable, Dict, Generator, Optional, Type
 
 from .error_wrappers import ValidationError
 from .errors import DataclassTypeError
+from .fields import Required
 from .main import create_model, validate_model
 from .utils import AnyType
 
@@ -72,7 +73,10 @@ def _process_class(
     _cls.__post_init__ = _pydantic_post_init
     cls = dataclasses._process_class(_cls, init, repr, eq, order, unsafe_hash, frozen)  # type: ignore
 
-    fields: Dict[str, Any] = {name: (field.type, field.default) for name, field in cls.__dataclass_fields__.items()}
+    fields: Dict[str, Any] = {
+        name: (field.type, field.default if field.default != dataclasses.MISSING else Required)
+        for name, field in cls.__dataclass_fields__.items()
+    }
     cls.__post_init_original__ = post_init_original
 
     cls.__pydantic_model__ = create_model(cls.__name__, __config__=config, __module__=_cls.__module__, **fields)

tests/test_dataclasses.py

@@ -1,4 +1,5 @@
 import dataclasses
+from datetime import datetime
 
 import pytest
 
@@ -260,3 +261,43 @@ def test_nested_dataclass_model():
 
     navbar = Outer(n=Nested(number='1'))
     assert navbar.n.number == 1
+
+
+def test_fields():
+    @pydantic.dataclasses.dataclass
+    class User:
+        id: int
+        name: str = 'John Doe'
+        signup_ts: datetime = None
+
+    user = User(id=123)
+    fields = user.__pydantic_model__.__fields__
+
+    assert fields['id'].required is True
+    assert fields['id'].default is None
+
+    assert fields['name'].required is False
+    assert fields['name'].default == 'John Doe'
+
+    assert fields['signup_ts'].required is False
+    assert fields['signup_ts'].default is None
+
+
+def test_schema():
+    @pydantic.dataclasses.dataclass
+    class User:
+        id: int
+        name: str = 'John Doe'
+        signup_ts: datetime = None
+
+    user = User(id=123)
+    assert user.__pydantic_model__.schema() == {
+        'title': 'User',
+        'type': 'object',
+        'properties': {
+            'id': {'title': 'Id', 'type': 'integer'},
+            'name': {'title': 'Name', 'default': 'John Doe', 'type': 'string'},
+            'signup_ts': {'title': 'Signup_Ts', 'type': 'string', 'format': 'date-time'},
+        },
+        'required': ['id'],
+    }