fix: resolve forward refs for inherited dataclasses (#2220)

* fix: resolve forward refs for inherited dataclasses

closes #1668

* chore: add change file

* fix: make test work everywhere

* chore: rename file just in case

As it doesn't solve the target issue, let's change the PR number

* docs: update change description

changes/2220-PrettyWood.md

@@ -0,0 +1 @@
+Resolve forward refs for stdlib dataclasses converted into _pydantic_ ones

pydantic/dataclasses.py

@@ -5,6 +5,7 @@ from .error_wrappers import ValidationError
 from .errors import DataclassTypeError
 from .fields import Required
 from .main import create_model, validate_model
+from .typing import resolve_annotations
 from .utils import ClassAttribute
 
 if TYPE_CHECKING:
@@ -128,7 +129,7 @@ def _process_class(
             _cls.__name__,
             (_cls,),
             {
-                '__annotations__': _cls.__annotations__,
+                '__annotations__': resolve_annotations(_cls.__annotations__, _cls.__module__),
                 '__post_init__': _pydantic_post_init,
                 # attrs for pickle to find this class
                 '__module__': __name__,

tests/test_forward_ref.py

@@ -4,6 +4,7 @@ from typing import Optional, Tuple
 import pytest
 
 from pydantic import BaseModel, ConfigError, ValidationError
+from pydantic.typing import Literal
 
 skip_pre_37 = pytest.mark.skipif(sys.version_info < (3, 7), reason='testing >= 3.7 behaviour only')
 
@@ -480,6 +481,32 @@ def test_forward_ref_with_create_model(create_module):
         assert instance.sub.dict() == {'foo': 'bar'}
 
 
+@skip_pre_37
+@pytest.mark.skipif(not Literal, reason='typing_extensions not installed')
+def test_resolve_forward_ref_dataclass(create_module):
+    module = create_module(
+        # language=Python
+        """
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from pydantic import BaseModel
+from pydantic.typing import Literal
+
+@dataclass
+class Base:
+    literal: Literal[1, 2]
+
+class What(BaseModel):
+    base: Base
+        """
+    )
+
+    m = module.What(base=module.Base(literal=1))
+    assert m.base.literal == 1
+
+
 def test_nested_forward_ref():
     class NestedTuple(BaseModel):
         x: Tuple[int, Optional['NestedTuple']]  # noqa: F821