fix: support custom root type with nested models in parse_obj

changes/2238-PrettyWood.md

@@ -0,0 +1 @@
+Support custom root type (aka `__root__`) when using `parse_obj()` with nested models

pydantic/main.py

@@ -509,12 +509,18 @@ def json(
         return self.__config__.json_dumps(data, default=encoder, **dumps_kwargs)
 
     @classmethod
-    def parse_obj(cls: Type['Model'], obj: Any) -> 'Model':
+    def _enforce_dict_if_root(cls, obj: Any) -> Any:
         if cls.__custom_root_type__ and (
             not (isinstance(obj, dict) and obj.keys() == {ROOT_KEY}) or cls.__fields__[ROOT_KEY].shape == SHAPE_MAPPING
         ):
-            obj = {ROOT_KEY: obj}
-        elif not isinstance(obj, dict):
+            return {ROOT_KEY: obj}
+        else:
+            return obj
+
+    @classmethod
+    def parse_obj(cls: Type['Model'], obj: Any) -> 'Model':
+        obj = cls._enforce_dict_if_root(obj)
+        if not isinstance(obj, dict):
             try:
                 obj = dict(obj)
             except (TypeError, ValueError) as e:
@@ -662,14 +668,13 @@ def __get_validators__(cls) -> 'CallableGenerator':
 
     @classmethod
     def validate(cls: Type['Model'], value: Any) -> 'Model':
+        value = cls._enforce_dict_if_root(value)
         if isinstance(value, dict):
             return cls(**value)
         elif isinstance(value, cls):
             return value.copy()
         elif cls.__config__.orm_mode:
             return cls.from_orm(value)
-        elif cls.__custom_root_type__:
-            return cls.parse_obj(value)
         else:
             try:
                 value_as_dict = dict(value)

tests/test_main.py

@@ -1120,6 +1120,60 @@ class MyModel(BaseModel):
     ]
 
 
+def test_parse_obj_nested_root():
+    class Pokemon(BaseModel):
+        name: str
+        level: int
+
+    class Pokemons(BaseModel):
+        __root__: List[Pokemon]
+
+    class Player(BaseModel):
+        rank: int
+        pokemons: Pokemons
+
+    class Players(BaseModel):
+        __root__: Dict[str, Player]
+
+    class Tournament(BaseModel):
+        players: Players
+        city: str
+
+    payload = {
+        'players': {
+            'Jane': {
+                'rank': 1,
+                'pokemons': [
+                    {
+                        'name': 'Pikachu',
+                        'level': 100,
+                    },
+                    {
+                        'name': 'Bulbasaur',
+                        'level': 13,
+                    },
+                ],
+            },
+            'Tarzan': {
+                'rank': 2,
+                'pokemons': [
+                    {
+                        'name': 'Jigglypuff',
+                        'level': 7,
+                    },
+                ],
+            },
+        },
+        'city': 'Qwerty',
+    }
+
+    tournament = Tournament.parse_obj(payload)
+    assert tournament.city == 'Qwerty'
+    assert len(tournament.players.__root__) == 2
+    assert len(tournament.players.__root__['Jane'].pokemons.__root__) == 2
+    assert tournament.players.__root__['Jane'].pokemons.__root__[0].name == 'Pikachu'
+
+
 def test_untouched_types():
     from pydantic import BaseModel