Add Pydantic Json field support (#79)

pydantic_settings/sources.py

@@ -9,7 +9,7 @@
 from pathlib import Path
 from typing import TYPE_CHECKING, Any, List, Mapping, Sequence, Tuple, Union, cast
 
-from pydantic import AliasChoices, AliasPath, BaseModel
+from pydantic import AliasChoices, AliasPath, BaseModel, Json
 from pydantic._internal._typing_extra import origin_is_union
 from pydantic._internal._utils import deep_update, lenient_issubclass
 from pydantic.fields import FieldInfo
@@ -68,7 +68,7 @@ def field_is_complex(self, field: FieldInfo) -> bool:
         Returns:
             Whether the field is complex.
         """
-        return _annotation_is_complex(field.annotation)
+        return _annotation_is_complex(field.annotation, field.metadata)
 
     def prepare_field_value(self, field_name: str, field: FieldInfo, value: Any, value_is_complex: bool) -> Any:
         """
@@ -611,7 +611,9 @@ def read_env_file(
         return file_vars
 
 
-def _annotation_is_complex(annotation: type[Any] | None) -> bool:
+def _annotation_is_complex(annotation: type[Any] | None, metadata: list[Any]) -> bool:
+    if any(isinstance(md, Json) for md in metadata):  # type: ignore[misc]
+        return False
     origin = get_origin(annotation)
     return (
         _annotation_is_complex_inner(annotation)

tests/test_settings.py

@@ -15,6 +15,7 @@
     ConfigDict,
     Field,
     HttpUrl,
+    Json,
     SecretStr,
     ValidationError,
 )
@@ -1652,3 +1653,48 @@ class Settings(BaseSettings):
     env.set('foobar_apple', 'has_prefix')
     s = Settings(_env_prefix='foobar_')
     assert s.apple == 'has_prefix'
+
+
+def test_env_json_field(env):
+    class Settings(BaseSettings):
+        x: Json
+
+    env.set('x', '{"foo": "bar"}')
+
+    s = Settings()
+    assert s.x == {'foo': 'bar'}
+
+    env.set('x', 'test')
+    with pytest.raises(ValidationError) as exc_info:
+        Settings()
+    assert exc_info.value.errors(include_url=False) == [
+        {
+            'type': 'json_invalid',
+            'loc': ('x',),
+            'msg': 'Invalid JSON: expected ident at line 1 column 2',
+            'input': 'test',
+            'ctx': {'error': 'expected ident at line 1 column 2'},
+        }
+    ]
+
+
+def test_env_json_field_dict(env):
+    class Settings(BaseSettings):
+        x: Json[Dict[str, int]]
+
+    env.set('x', '{"foo": 1}')
+
+    s = Settings()
+    assert s.x == {'foo': 1}
+
+    env.set('x', '{"foo": "bar"}')
+    with pytest.raises(ValidationError) as exc_info:
+        Settings()
+    assert exc_info.value.errors(include_url=False) == [
+        {
+            'type': 'int_parsing',
+            'loc': ('x', 'foo'),
+            'msg': 'Input should be a valid integer, unable to parse string as an integer',
+            'input': 'bar',
+        }
+    ]