fix for model subclass serialization in unions (pydantic#632)

src/serializers/fields.rs

@@ -6,6 +6,7 @@ use pyo3::types::{PyDict, PyString};
 use ahash::AHashMap;
 use serde::ser::SerializeMap;
 
+use crate::serializers::extra::SerCheck;
 use crate::PydanticSerializationUnexpectedValue;
 
 use super::computed_fields::ComputedFields;
@@ -75,7 +76,7 @@ fn exclude_default(value: &PyAny, extra: &Extra, serializer: &CombinedSerializer
     Ok(false)
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Eq, PartialEq)]
 pub(super) enum FieldsMode {
     // typeddict with no extra items
     SimpleDict,
@@ -196,10 +197,10 @@ impl TypeSerializer for GeneralFieldsSerializer {
                     if field.required {
                         used_req_fields += 1;
                     }
-                } else if matches!(self.mode, FieldsMode::TypedDictAllow) {
+                } else if self.mode == FieldsMode::TypedDictAllow {
                     let value = infer_to_python(value, next_include, next_exclude, &extra)?;
                     output_dict.set_item(key, value)?;
-                } else if extra.check.enabled() {
+                } else if extra.check == SerCheck::Strict {
                     return Err(PydanticSerializationUnexpectedValue::new_err(None));
                 }
             }
@@ -281,11 +282,12 @@ impl TypeSerializer for GeneralFieldsSerializer {
                             map.serialize_entry(&output_key, &s)?;
                         }
                     }
-                } else if matches!(self.mode, FieldsMode::TypedDictAllow) {
+                } else if self.mode == FieldsMode::TypedDictAllow {
                     let output_key = infer_json_key(key, &extra).map_err(py_err_se_err)?;
                     let s = SerializeInfer::new(value, next_include, next_exclude, &extra);
                     map.serialize_entry(&output_key, &s)?
                 }
+                // no error case here since unions (which need the error case) use `to_python(..., mode='json')`
             }
         }
         // this is used to include `__pydantic_extra__` in serialization on models

src/serializers/type_serializers/model.rs

@@ -109,9 +109,10 @@ fn has_extra(schema: &PyDict, config: Option<&PyDict>) -> PyResult<bool> {
 
 impl ModelSerializer {
     fn allow_value(&self, value: &PyAny, extra: &Extra) -> PyResult<bool> {
+        let class = self.class.as_ref(value.py());
         match extra.check {
-            SerCheck::Strict => Ok(value.get_type().is(self.class.as_ref(value.py()))),
-            SerCheck::Lax => value.is_instance(self.class.as_ref(value.py())),
+            SerCheck::Strict => Ok(value.get_type().is(class)),
+            SerCheck::Lax => value.is_instance(class),
             SerCheck::None => value.hasattr(intern!(value.py(), "__dict__")),
         }
     }

tests/serializers/test_union.py

@@ -1,3 +1,4 @@
+import dataclasses
 import json
 import re
 
@@ -179,17 +180,16 @@ def test_typed_dict_literal():
 
 
 def test_typed_dict_missing():
-    """
-    TODO, needs tests for each case
-    """
     s = SchemaSerializer(
         core_schema.union_schema(
             [
                 core_schema.typed_dict_schema(dict(foo=core_schema.typed_dict_field(core_schema.int_schema()))),
                 core_schema.typed_dict_schema(
                     dict(
                         foo=core_schema.typed_dict_field(
-                            core_schema.int_schema(serialization=core_schema.format_ser_schema('04d'))
+                            core_schema.int_schema(
+                                serialization=core_schema.format_ser_schema('04d', when_used='always')
+                            )
                         ),
                         bar=core_schema.typed_dict_field(core_schema.int_schema()),
                     )
@@ -201,7 +201,8 @@ def test_typed_dict_missing():
     assert s.to_python(dict(foo=1)) == {'foo': 1}
     assert s.to_python(dict(foo=1), mode='json') == {'foo': 1}
     assert s.to_json(dict(foo=1)) == b'{"foo":1}'
-    assert s.to_python(dict(foo=1, bar=2)) == {'foo': 1, 'bar': 2}
+
+    assert s.to_python(dict(foo=1, bar=2)) == {'foo': '0001', 'bar': 2}
     assert s.to_python(dict(foo=1, bar=2), mode='json') == {'foo': '0001', 'bar': 2}
     assert s.to_json(dict(foo=1, bar=2)) == b'{"foo":"0001","bar":2}'
 
@@ -269,3 +270,93 @@ def test_typed_dict_different_fields():
     assert s.to_python(dict(spam=1, ham=2)) == {'spam': 1, 'ham': 2}
     assert s.to_python(dict(spam=1, ham=2), mode='json') == {'spam': 1, 'ham': '0002'}
     assert s.to_json(dict(spam=1, ham=2)) == b'{"spam":1,"ham":"0002"}'
+
+
+def test_dataclass_union():
+    @dataclasses.dataclass
+    class BaseUser:
+        name: str
+
+    @dataclasses.dataclass
+    class User(BaseUser):
+        surname: str
+
+    @dataclasses.dataclass
+    class DBUser(User):
+        password_hash: str
+
+    @dataclasses.dataclass
+    class Item:
+        name: str
+        price: float
+
+    user_schema = core_schema.dataclass_schema(
+        User,
+        core_schema.dataclass_args_schema(
+            'User',
+            [
+                core_schema.dataclass_field(name='name', schema=core_schema.str_schema()),
+                core_schema.dataclass_field(name='surname', schema=core_schema.str_schema()),
+            ],
+        ),
+        ['name', 'surname'],
+    )
+    item_schema = core_schema.dataclass_schema(
+        Item,
+        core_schema.dataclass_args_schema(
+            'Item',
+            [
+                core_schema.dataclass_field(name='name', schema=core_schema.str_schema()),
+                core_schema.dataclass_field(name='price', schema=core_schema.float_schema()),
+            ],
+        ),
+        ['name', 'price'],
+    )
+    s = SchemaSerializer(core_schema.union_schema([user_schema, item_schema]))
+    assert s.to_python(User(name='foo', surname='bar')) == {'name': 'foo', 'surname': 'bar'}
+    assert s.to_python(DBUser(name='foo', surname='bar', password_hash='x')) == {'name': 'foo', 'surname': 'bar'}
+    assert s.to_json(DBUser(name='foo', surname='bar', password_hash='x')) == b'{"name":"foo","surname":"bar"}'
+
+
+def test_model_union():
+    class BaseUser:
+        def __init__(self, name: str):
+            self.name = name
+
+    class User(BaseUser):
+        def __init__(self, name: str, surname: str):
+            super().__init__(name)
+            self.surname = surname
+
+    class DBUser(User):
+        def __init__(self, name: str, surname: str, password_hash: str):
+            super().__init__(name, surname)
+            self.password_hash = password_hash
+
+    class Item:
+        def __init__(self, name: str, price: float):
+            self.name = name
+            self.price = price
+
+    user_schema = core_schema.model_schema(
+        User,
+        core_schema.model_fields_schema(
+            {
+                'name': core_schema.model_field(schema=core_schema.str_schema()),
+                'surname': core_schema.model_field(schema=core_schema.str_schema()),
+            }
+        ),
+    )
+    item_schema = core_schema.model_schema(
+        Item,
+        core_schema.model_fields_schema(
+            {
+                'name': core_schema.model_field(schema=core_schema.str_schema()),
+                'price': core_schema.model_field(schema=core_schema.float_schema()),
+            }
+        ),
+    )
+    s = SchemaSerializer(core_schema.union_schema([user_schema, item_schema]))
+    assert s.to_python(User(name='foo', surname='bar')) == {'name': 'foo', 'surname': 'bar'}
+    assert s.to_python(DBUser(name='foo', surname='bar', password_hash='x')) == {'name': 'foo', 'surname': 'bar'}
+    assert s.to_json(DBUser(name='foo', surname='bar', password_hash='x')) == b'{"name":"foo","surname":"bar"}'