fix(pydantic): allow pydantic model instances as defaults (jpmorganch…

…ase#64)

src/py_avro_schema/_schemas.py

@@ -862,6 +862,7 @@ def _record_field(self, py_field: dataclasses.Field) -> RecordField:
             default=default,
             options=self.options,
         )
+
         return field_obj
 
 
@@ -899,6 +900,9 @@ def _record_field(self, name: str, py_field: pydantic.fields.FieldInfo) -> Recor
             docs=py_field.description or "",
             options=self.options,
         )
+        # allow to use pydantic models as default values
+        if PydanticSchema.handles_type(default.__class__):
+            field_obj.default = default.model_dump(mode="json")  # type: ignore
         return field_obj
 
     def _annotation(self, field_name: str) -> Type:

tests/test_pydantic.py

@@ -523,3 +523,28 @@ class PyType(Base):
         ],
     }
     assert_schema(PyType, expected)
+
+
+def test_base_model_defaults():
+    class Default(pydantic.BaseModel):
+        field_a: str = "default_a"
+
+    class PyType(pydantic.BaseModel):
+        default: Default = pydantic.Field(..., default_factory=Default)
+
+    expected = {
+        "fields": [
+            {
+                "default": {"field_a": "default_a"},
+                "name": "default",
+                "type": {
+                    "fields": [{"default": "default_a", "name": "field_a", "type": "string"}],
+                    "name": "Default",
+                    "type": "record",
+                },
+            }
+        ],
+        "name": "PyType",
+        "type": "record",
+    }
+    assert_schema(PyType, expected)