Use a default serializer that is not only for date types

This would allow making more general changes here. I am also adding
serialization of bytes type into base64.

jupyter_client/jsonutil.py

@@ -3,6 +3,7 @@
 # Distributed under the terms of the Modified BSD License.
 import re
 import warnings
+from binascii import b2a_base64
 from datetime import datetime
 from typing import Optional
 from typing import Union
@@ -91,9 +92,21 @@ def squash_dates(obj):
 
 
 def date_default(obj):
- """default function for packing datetime objects in JSON."""
+ """DEPRECATED: Use jupyter_client.jsonutil.json_default"""
+ warnings.warn(
+ "date_default is deprecated since jupyter_client 7.0.0."
+ " Use jupyter_client.jsonutil.json_default.",
+ stacklevel=2,
+ )
+ return json_default(obj)
+
+
+def json_default(obj):
+ """default function for packing objects in JSON."""
  if isinstance(obj, datetime):
  obj = _ensure_tzinfo(obj)
- return obj.isoformat().replace("+00:00", "Z")
+ return obj.isoformat().replace('+00:00', 'Z')
+ elif isinstance(obj, bytes):
+ return b2a_base64(obj).decode('ascii')
  else:
  raise TypeError("%r is not JSON serializable" % obj)

jupyter_client/session.py

@@ -49,8 +49,8 @@
 
 from jupyter_client import protocol_version
 from jupyter_client.adapter import adapt
-from jupyter_client.jsonutil import date_default
 from jupyter_client.jsonutil import extract_dates
+from jupyter_client.jsonutil import json_default
 from jupyter_client.jsonutil import squash_dates
 
 
@@ -94,7 +94,7 @@ def squash_unicode(obj):
 def json_packer(obj):
  return jsonapi.dumps(
  obj,
- default=date_default,
+ default=json_default,
  ensure_ascii=False,
  allow_nan=False,
  )

jupyter_client/tests/test_jsonutil.py

@@ -65,14 +65,14 @@ def test_parse_ms_precision():
  assert isinstance(parsed, str)
 
 
-def test_date_default():
+def test_json_default():
  naive = datetime.datetime.now()
  local = tzoffset("Local", -8 * 3600)
  other = tzoffset("Other", 2 * 3600)
  data = dict(naive=naive, utc=utcnow(), withtz=naive.replace(tzinfo=other))
  with mock.patch.object(jsonutil, "tzlocal", lambda: local):
  with pytest.deprecated_call(match="Please add timezone info"):
- jsondata = json.dumps(data, default=jsonutil.date_default)
+ jsondata = json.dumps(data, default=jsonutil.json_default)
  assert "Z" in jsondata
  assert jsondata.count("Z") == 1
  extracted = jsonutil.extract_dates(json.loads(jsondata))