Fix a bug when using BaseSettings with RootModel (#120)

Author: hramezani

pydantic_settings/sources.py

@@ -184,7 +184,7 @@ class Sub(BaseModel):
             class Settings(BaseSettings):
                 nested: Sub
 
-                model_config = ConfigDict(env_nested_delimiter='__')
+                model_config = SettingsConfigDict(env_nested_delimiter='__')
             ```
 
         Then:
@@ -241,7 +241,11 @@ def __call__(self) -> dict[str, Any]:
                 ) from e
 
             if field_value is not None:
-                if not self.case_sensitive and lenient_issubclass(field.annotation, BaseModel):
+                if (
+                    not self.case_sensitive
+                    and lenient_issubclass(field.annotation, BaseModel)
+                    and isinstance(field_value, dict)
+                ):
                     data[field_key] = self._replace_field_names_case_insensitively(field, field_value)
                 else:
                     data[field_key] = field_value

tests/test_settings.py

@@ -15,6 +15,7 @@
     Field,
     HttpUrl,
     Json,
+    RootModel,
     SecretStr,
     ValidationError,
 )
@@ -1775,3 +1776,18 @@ class Settings(BaseSettings, env_prefix='foobar_', title='Test Settings Model'):
     env.set('foobar_apple', 'has_prefix')
     s = Settings()
     assert s.apple == 'has_prefix'
+
+
+def test_root_model_as_field(env):
+    class Foo(BaseModel):
+        x: int
+        y: Dict[str, int]
+
+    FooRoot = RootModel[List[Foo]]
+
+    class Settings(BaseSettings):
+        z: FooRoot
+
+    env.set('z', '[{"x": 1, "y": {"foo": 1}}, {"x": 2, "y": {"foo": 2}}]')
+    s = Settings()
+    assert s.model_dump() == {'z': [{'x': 1, 'y': {'foo': 1}}, {'x': 2, 'y': {'foo': 2}}]}