fix: handle multiple annotations when dtype is present in Field

.gitignore

@@ -132,3 +132,5 @@ dmypy.json
 
 # Pyre type checker
 .pyre/
+
+.vscode/

src/patito/pydantic.py

@@ -218,7 +218,8 @@ def _valid_dtypes(  # noqa: C901
                     f"No valid dtype mapping found for column '{column}'."
                 )
             return [pl.List(dtype) for dtype in item_dtypes]
-        if "dtype" in props:
+
+        if "dtype" in props and 'anyOf' not in props:
             return [
                 props["dtype"],
             ]

tests/test_model.py

@@ -454,3 +454,11 @@ class Model(pt.Model):
     assert fields["d"].dtype is not None
     assert "unique" in fields["e"]._attributes_set
     assert fields["e"].unique is not None
+
+
+def test_nullable_columns():
+    class Test(pt.Model):
+        foo: str | None = pt.Field(dtype=pl.Utf8)
+
+    assert Test.nullable_columns == {"foo"}
+    assert set(Test.valid_dtypes['foo']) == {pl.Utf8, pl.Null}

tests/test_polars.py

@@ -253,3 +253,5 @@ class Model(pt.Model):
 
     # Or a list of columns
     assert df.drop(["column_1", "column_2"]).columns == []
+
+