fix: Incorrect to_schema generation for dataclass using ResultConverter

sqlspec/mixins.py

@@ -1,3 +1,4 @@
+import dataclasses
 import datetime
 from abc import abstractmethod
 from collections.abc import Sequence
@@ -257,10 +258,10 @@ def to_schema(
             if not isinstance(data, Sequence):
                 return cast("ModelT", data)
             return cast("Sequence[ModelT]", data)
-        if is_dataclass(schema_type):
+        if dataclasses.is_dataclass(schema_type):
             if not isinstance(data, Sequence):
                 # data is assumed to be dict[str, Any] as per the method's overloads
-                return cast("ModelDTOT", schema_type(**data))  # type: ignore[operator]
+                return cast("ModelDTOT", schema_type(data))  # type: ignore[operator]
             # data is assumed to be Sequence[dict[str, Any]]
             return cast("Sequence[ModelDTOT]", [schema_type(**item) for item in data])  # type: ignore[operator]
         if is_msgspec_struct(schema_type):

tests/unit/test_mixins.py

@@ -0,0 +1,72 @@
+"""Tests for mixins utilities."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Any, ClassVar
+
+import pytest
+from msgspec import Struct
+from pydantic import BaseModel
+
+from sqlspec.mixins import (
+    ResultConverter
+)
+from sqlspec.typing import (
+    Empty,
+    is_dataclass_instance,
+)
+
+
+@dataclass
+class SampleDataclass:
+    """Sample dataclass for testing."""
+
+    name: str
+    value: int | None = None
+    empty_field: Any = Empty
+    meta: ClassVar[str] = "test"
+
+
+class SamplePydanticModel(BaseModel):
+    """Sample Pydantic model for testing."""
+
+    name: str
+    value: int | None = None
+
+
+class SampleMsgspecModel(Struct):
+    """Sample Msgspec model for testing."""
+
+    name: str
+    value: int | None = None
+
+
+@pytest.fixture(scope="session")
+def sample_dataclass() -> SampleDataclass:
+    """Create a sample dataclass instance."""
+    return SampleDataclass(name="test", value=42)
+
+
+@pytest.fixture(scope="session")
+def sample_pydantic() -> SamplePydanticModel:
+    """Create a sample Pydantic model instance."""
+    return SamplePydanticModel(name="test", value=42)
+
+
+@pytest.fixture(scope="session")
+def sample_msgspec() -> SampleMsgspecModel:
+    """Create a sample Msgspec model instance."""
+    return SampleMsgspecModel(name="test", value=42)
+
+
+@pytest.fixture(scope="session")
+def sample_dict() -> dict[str, Any]:
+    """Create a sample dictionary."""
+    return {"name": "test", "value": 42}
+
+
+def test_is_result_converter_dataclass(sample_dataclass: SampleDataclass) -> None:
+    """Test dataclass type checking."""
+    assert is_dataclass_instance(ResultConverter.to_schema(data=SampleDataclass(name="test", value=42), schema_type=SampleDataclass))
+