Refactor packer/unpacker change handling for improved readability

Author: fleming79

CHANGELOG.md

@@ -9,7 +9,6 @@
 ### Enhancements made
 
 - Support psutil for finding network addresses [#1033](https://github.com/jupyter/jupyter_client/pull/1033) ([@juliangilbey](https://github.com/juliangilbey))
-- Add new functions `orjson_packer`, `orjson_unpacker`, `msgpack_packer` and `msgpack_unpacker`
 
 ### Bugs fixed
 

jupyter_client/session.py

@@ -393,28 +393,21 @@ class Session(Configurable):
 
     @observe("packer", "unpacker")
     def _packer_unpacker_changed(self, change: t.Any) -> None:
-        new = change["new"]
-        new_ = new.lower()
-        if new_ == "orjson" and orjson:
-            self.pack = orjson_packer
-            self.unpack = orjson_unpacker
-            self.packer = self.unpacker = new
-        elif new_ in ["json", "orjson"]:
-            self.pack = json_packer
-            self.unpack = json_unpacker
-            self.packer = self.unpacker = new
-        elif new_ == "pickle":
-            self.pack = pickle_packer
-            self.unpack = pickle_unpacker
-            self.packer = self.unpacker = new
-        elif new_ == "msgpack":
-            self.pack = msgpack_packer
-            self.unpack = msgpack_unpacker
-            self.packer = self.unpacker = new
+        new = change["new"].lower()
+        if new == "orjson" and orjson:
+            self.pack, self.unpack = orjson_packer, orjson_unpacker
+        elif new == "json" or new == "orjson":
+            self.pack, self.unpack = json_packer, json_unpacker
+        elif new == "pickle":
+            self.pack, self.unpack = pickle_packer, pickle_unpacker
+        elif new == "msgpack" and msgpack:
+            self.pack, self.unpack = msgpack_packer, msgpack_unpacker
         else:
-            obj = import_item(str(new))
+            obj = import_item(str(change["new"]))
             name = "pack" if change["name"] == "packer" else "unpack"
             self.set_trait(name, obj)
+            return
+        self.packer = self.unpacker = change["new"]
 
     session = CUnicode("", config=True, help="""The UUID identifying this session.""")
 

tests/test_session.py

@@ -524,12 +524,16 @@ def test_squash_unicode():
     assert ss.squash_unicode("hi") == b"hi"
 
 
+_sample_time = datetime(2021, 4, 1, 12, tzinfo=tzlocal())
+_sample_time_string = ss.json_default(_sample_time)
+
+
 @pytest.mark.parametrize(
     ["description", "data"],
     [
         ("dict", [{"a": 1}, [{"a": 1}]]),
         ("infinite", [math.inf, ["inf", None]]),
-        ("datetime", [datetime(2021, 4, 1, 12, tzinfo=tzlocal()), ["2021-04-01T12:00:00+11:00"]]),
+        ("datetime", [_sample_time, [_sample_time_string]]),
     ],
 )
 @pytest.mark.parametrize(["packer", "pack", "unpack"], serializers)