Accept any type as default json parser value

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## 10.1.0 (unreleased)
+
+Features:
+
+- Allow `default` for `env.json` to be a `dict` or `list` ([#240](https://github.com/sloria/environs/pull/240)).
+  Thanks [tomgrin10](https://github.com/tomgrin10) and [bvanelli](https://github.com/bvanelli) for the PRs.
+
 ## 10.0.0 (2023-12-15)
 
 Features:

environs/__init__.py

@@ -231,9 +231,14 @@ def _preprocess_dict(
     }
 
 
-def _preprocess_json(value: str, **kwargs):
+def _preprocess_json(value: typing.Union[str, typing.Mapping, typing.List], **kwargs):
     try:
-        return pyjson.loads(value)
+        if isinstance(value, str):
+            return pyjson.loads(value)
+        elif isinstance(value, dict) or isinstance(value, list) or value is None:
+            return value
+        else:
+            raise ma.ValidationError("Not valid JSON.")
     except pyjson.JSONDecodeError as error:
         raise ma.ValidationError("Not valid JSON.") from error
 

tests/test_environs.py

@@ -198,6 +198,13 @@ def test_invalid_json_raises_error(self, set_env, env):
             env.json("JSON")
         assert "Not valid JSON." in exc.value.args[0]
 
+    def test_json_default(self, set_env, env):
+        assert env.json("JSON", {"foo": "bar"}) == {"foo": "bar"}
+        assert env.json("JSON", ["foo", "bar"]) == ["foo", "bar"]
+        with pytest.raises(environs.EnvError) as exc:
+            env.json("JSON", int)  # a builtin is not a valid json
+        assert "Not valid JSON." in exc.value.args[0]
+
     def test_datetime_cast(self, set_env, env):
         dtime = dt.datetime.utcnow()
         set_env({"DTIME": dtime.isoformat()})