Allow JSON serialization to work with json.dumps (#655)

param/__init__.py

@@ -1058,12 +1058,12 @@ def _validate(self, val):
     @classmethod
     def serialize(cls, value):
         if value is None:
-            return 'null'
+            return None
         return list(value) # As JSON has no tuple representation
 
     @classmethod
     def deserialize(cls, value):
-        if value == 'null':
+        if value == 'null' or value is None:
             return None
         return tuple(value) # As JSON has no tuple representation
 
@@ -1519,12 +1519,12 @@ def __init__(self, default=None, **params):
     @classmethod
     def serialize(cls, value):
         if value is None:
-            return 'null'
+            return None
         return value.tolist()
 
     @classmethod
     def deserialize(cls, value):
-        if value == 'null':
+        if value == 'null' or value is None:
             return None
         from numpy import asarray
         return asarray(value)
@@ -1606,12 +1606,12 @@ def _validate(self, val):
     @classmethod
     def serialize(cls, value):
         if value is None:
-            return 'null'
+            return None
         return value.to_dict('records')
 
     @classmethod
     def deserialize(cls, value):
-        if value == 'null':
+        if value == 'null' or value is None:
             return None
         from pandas import DataFrame as pdDFrame
         return pdDFrame(value)
@@ -1978,14 +1978,14 @@ def _validate_step(self, val, step):
     @classmethod
     def serialize(cls, value):
         if value is None:
-            return 'null'
+            return None
         if not isinstance(value, (dt.datetime, dt.date)): # i.e np.datetime64
             value = value.astype(dt.datetime)
         return value.strftime("%Y-%m-%dT%H:%M:%S.%f")
 
     @classmethod
     def deserialize(cls, value):
-        if value == 'null':
+        if value == 'null' or value is None:
             return None
         return dt.datetime.strptime(value, "%Y-%m-%dT%H:%M:%S.%f")
 
@@ -2016,12 +2016,12 @@ def _validate_step(self, val, step):
     @classmethod
     def serialize(cls, value):
         if value is None:
-            return 'null'
+            return None
         return value.strftime("%Y-%m-%d")
 
     @classmethod
     def deserialize(cls, value):
-        if value == 'null':
+        if value == 'null' or value is None:
             return None
         return dt.datetime.strptime(value, "%Y-%m-%d").date()
 
@@ -2176,7 +2176,7 @@ def _validate_value(self, val, allow_None):
     @classmethod
     def serialize(cls, value):
         if value is None:
-            return 'null'
+            return None
         # List as JSON has no tuple representation
         serialized = []
         for v in value:
@@ -2191,7 +2191,7 @@ def serialize(cls, value):
         return serialized
 
     def deserialize(cls, value):
-        if value == 'null':
+        if value == 'null' or value is None:
             return None
         deserialized = []
         for v in value:
@@ -2227,13 +2227,13 @@ def _validate_value(self, val, allow_None):
     @classmethod
     def serialize(cls, value):
         if value is None:
-            return 'null'
+            return None
         # As JSON has no tuple representation
         return [v.strftime("%Y-%m-%d") for v in value]
 
     @classmethod
     def deserialize(cls, value):
-        if value == 'null':
+        if value == 'null' or value is None:
             return None
         # As JSON has no tuple representation
         return tuple([dt.datetime.strptime(v, "%Y-%m-%d").date() for v in value])

tests/API1/testdateparam.py

@@ -1,8 +1,8 @@
 """
 Unit test for Date parameters.
 """
-
-
+import sys
+import json
 import datetime as dt
 import param
 from . import API1TestCase
@@ -52,3 +52,19 @@ def test_get_soft_bounds(self):
         self.assertEqual(q.get_soft_bounds(), (dt.datetime(2017,2,1),
                                                dt.datetime(2017,2,25)))
 
+def test_date_serialization():
+    class User(param.Parameterized):
+        A = param.Date(default=None)
+
+    # Validate round is possible
+    User.param.deserialize_parameters(User.param.serialize_parameters())
+
+    if sys.version_info.major == 2:
+        return
+
+    serialized_data = '{"name": "User", "A": null}'
+    deserialized_data = {"name": "User", "A": None}
+
+    assert serialized_data == json.dumps(deserialized_data)
+    assert serialized_data == User.param.serialize_parameters()
+    assert deserialized_data == User.param.deserialize_parameters(serialized_data)