Fix issues due to the Parameterized private namespace

param/parameterized.py

@@ -845,15 +845,6 @@ def __new__(cls_, *args, **kwargs):
             values['precedence'] = 0
         return super().__new__(cls_, **values)
 
-    def __iter__(self):
-        """
-        Backward compatibility layer to allow tuple unpacking without
-        the precedence value. Important for Panel which creates a
-        custom Watcher and uses tuple unpacking. Will be dropped in
-        Param 3.x.
-        """
-        return iter(self[:-1])
-
     def __str__(self):
         cls = type(self)
         attrs = ', '.join([f'{f}={getattr(self, f)!r}' for f in cls._fields])
@@ -1412,6 +1403,9 @@ def __set__(self, obj, val):
                 _old = self.default
                 self.default = val
             else:
+                # When setting a Parameter before calling super.
+                if not isinstance(obj._param__private, _InstancePrivate):
+                    obj._param__private = _InstancePrivate()
                 _old = obj._param__private.values.get(self.name, self.default)
                 obj._param__private.values[self.name] = val
 
@@ -3627,6 +3621,7 @@ class _ClassPrivate:
         'disable_instance_params',
         'renamed',
         'params',
+        'initialized',
     ]
 
     def __init__(
@@ -3647,6 +3642,14 @@ def __init__(
         self.disable_instance_params = disable_instance_params
         self.renamed = renamed
         self.params = {} if params is None else params
+        self.initialized = False
+
+    def __getstate__(self):
+        return {slot: getattr(self, slot) for slot in self.__slots__}
+
+    def __setstate__(self, state):
+        for k, v in state.items():
+            setattr(self, k, v)
 
 
 class _InstancePrivate:
@@ -3699,6 +3702,13 @@ def __init__(
         # self.watchers = {} if watchers is None else watchers
         self.values = {} if values is None else values
 
+    def __getstate__(self):
+        return {slot: getattr(self, slot) for slot in self.__slots__}
+
+    def __setstate__(self, state):
+        for k, v in state.items():
+            setattr(self, k, v)
+
 
 class Parameterized(metaclass=ParameterizedMetaclass):
     """
@@ -3749,7 +3759,12 @@ class Foo(Parameterized):
     def __init__(self, **params):
         global object_count
 
-        self._param__private = _InstancePrivate()
+        # Setting a Parameter value in an __init__ block before calling
+        # Parameterized.__init__ (via super() generally) already sets the
+        # _InstancePrivate namespace over the _ClassPrivate namespace
+        # (see Parameter.__set__) so we shouldn't override it here.
+        if not isinstance(self._param__private, _InstancePrivate):
+            self._param__private = _InstancePrivate()
         self._param_watchers = {}
 
         # Skip generating a custom instance name when a class in the hierarchy

pyproject.toml

@@ -217,6 +217,7 @@ python_files = "test*.py"
 filterwarnings = [
   "error",
 ]
+xfail_strict = "true"
 
 [tool.coverage.report]
 omit = ["param/version.py"]

tests/testparameterizedobject.py

@@ -378,6 +378,142 @@ def test_remove_class_param_validation(self):
         with self.assertRaises(ValueError):
             TestPOValidation.value = 10
 
+    def test_instantiation_set_before_super(self):
+        count = 0
+        class P(param.Parameterized):
+
+            x = param.Parameter(0)
+
+            def __init__(self, x=1):
+                self.x = x
+                super().__init__()
+
+            @param.depends('x', watch=True)
+            def cb(self):
+                nonlocal count
+                count += 1
+
+        p = P()
+
+        assert p.x == 1
+        assert count == 0
+
+    def test_instantiation_set_before_super_contrived(self):
+        # https://github.com/holoviz/param/pull/790#discussion_r1263483293
+        class P(param.Parameterized):
+
+            value = param.String(default="A")
+
+            def __init__(self, depth=0):
+                self.value = 'B'
+                if depth < 2:
+                    self.sub = P(depth+1)
+                super().__init__()
+
+        p = P()
+
+        assert p.value == 'B'
+        assert p.sub.value == 'B'
+
+    def test_instantiation_set_before_super_subclass(self):
+        # Inspired by a HoloViews use case (GenericElementPlot, GenericOverlayPlot)
+        class A(param.Parameterized):
+
+            def __init__(self, batched=False, **params):
+                self.batched = batched
+                super().__init__(**params)
+
+        class B(A):
+
+            batched = param.Boolean()
+
+            def __init__(self, batched=True, **params):
+                super().__init__(batched=batched, **params)
+
+        a = A()
+        assert a.batched is False
+
+        # When b is instantiated the `batched` Parameter of B is set before
+        # Parameterized.__init__ is called.
+        b = B()
+        assert b.batched is True
+
+    def test_instantiation_param_objects_before_super_subclass(self):
+        # Testing https://github.com/holoviz/param/pull/420
+
+
+        class P(param.Parameterized):
+            x = param.Parameter()
+
+            def __init__(self):
+                objs = self.param.objects(instance='existing')
+                assert isinstance(objs, dict)
+                super().__init__()
+
+        P()
+
+    @pytest.mark.xfail(
+        raises=AttributeError,
+        reason='Behavior not defined when setting a constant parameter before calling super()',
+    )
+    def test_instantiation_set_before_super_constant(self):
+        count = 0
+        class P(param.Parameterized):
+
+            x = param.Parameter(0, constant=True)
+
+            def __init__(self, x=1):
+                self.x = x
+                super().__init__()
+
+            @param.depends('x', watch=True)
+            def cb(self):
+                nonlocal count
+                count += 1
+
+        p = P()
+
+        assert p.x == 1
+        assert count == 0
+
+    def test_instantiation_set_before_super_readonly(self):
+        class P(param.Parameterized):
+
+            x = param.Parameter(0, readonly=True)
+
+            def __init__(self, x=1):
+                self.x = x
+                super().__init__()
+
+        with pytest.raises(TypeError, match="Read-only parameter 'x' cannot be modified"):
+            P()
+
+    def test_parameter_constant_iadd_allowed(self):
+        # Testing https://github.com/holoviz/param/pull/400
+        class P(param.Parameterized):
+
+            list = param.List([], constant=True)
+
+        p = P()
+        p.list += [1, 2, 3]
+
+        # Just to make sure that normal setting is still forbidden
+        with pytest.raises(TypeError, match="Constant parameter 'list' cannot be modified"):
+            p.list = [0]
+
+    def test_parameter_constant_same_notallowed(self):
+        L = [0, 1]
+        class P(param.Parameterized):
+
+            list = param.List(L, constant=True)
+
+        p = P()
+
+        # instantiate is set to true internally so a deepcopy is made of L,
+        # it's no longer the same object
+        with pytest.raises(TypeError, match="Constant parameter 'list' cannot be modified"):
+            p.list = L
+
     def test_values(self):
         """Basic tests of params() method."""
 

tests/testpickle.py

@@ -29,24 +29,27 @@ class P1(param.Parameterized):
     x = param.Parameter()
 
 @pytest.mark.parametrize('pickler', [cloudpickle, pickle], indirect=True)
-def test_pickle_simple_class(pickler):
-    s = pickler.dumps(P1)
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_pickle_simple_class(pickler, protocol):
+    s = pickler.dumps(P1, protocol=protocol)
     cls = pickler.loads(s)
     assert cls is P1
 
 
 @pytest.mark.parametrize('pickler', [cloudpickle, pickle], indirect=True)
-def test_pickle_simple_instance(pickler):
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_pickle_simple_instance(pickler, protocol):
     p = P1()
-    s = pickler.dumps(p)
+    s = pickler.dumps(p, protocol=protocol)
     inst = pickler.loads(s)
     assert eq(p, inst)
 
 
 @pytest.mark.parametrize('pickler', [cloudpickle, pickle], indirect=True)
-def test_pickle_simple_instance_modif_after(pickler):
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_pickle_simple_instance_modif_after(pickler, protocol):
     p = P1()
-    s = pickler.dumps(p)
+    s = pickler.dumps(p, protocol=protocol)
     p.x = 'modified'
     inst = pickler.loads(s)
     assert not eq(p, inst)
@@ -88,16 +91,18 @@ class P2(param.Parameterized):
 
 
 @pytest.mark.parametrize('pickler', [cloudpickle, pickle], indirect=True)
-def test_pickle_all_parameters_class(pickler):
-    s = pickler.dumps(P2)
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_pickle_all_parameters_class(pickler, protocol):
+    s = pickler.dumps(P2, protocol=protocol)
     cls = pickler.loads(s)
     assert cls is P2
 
 
 @pytest.mark.parametrize('pickler', [cloudpickle, pickle], indirect=True)
-def test_pickle_all_parameters_instance(pickler):
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_pickle_all_parameters_instance(pickler, protocol):
     p = P2()
-    s = pickler.dumps(p)
+    s = pickler.dumps(p, protocol=protocol)
     inst = pickler.loads(s)
     assert eq(p, inst)
 
@@ -112,17 +117,19 @@ def cb(self):
 
 
 @pytest.mark.parametrize('pickler', [cloudpickle, pickle], indirect=True)
-def test_pickle_depends_watch_class(pickler):
-    s = pickler.dumps(P3)
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_pickle_depends_watch_class(pickler, protocol):
+    s = pickler.dumps(P3, protocol=protocol)
     cls = pickler.loads(s)
     assert cls is P3
 
 
 @pytest.mark.parametrize('pickler', [cloudpickle, pickle], indirect=True)
-def test_pickle_depends_watch_instance(pickler):
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_pickle_depends_watch_instance(pickler, protocol):
     # https://github.com/holoviz/param/issues/757
     p = P3()
-    s = pickler.dumps(p)
+    s = pickler.dumps(p, protocol=protocol)
     inst = pickler.loads(s)
     assert eq(p, inst)
 
@@ -167,27 +174,30 @@ def nested(self):
 
 
 @pytest.mark.parametrize('pickler', [cloudpickle, pickle], indirect=True)
-def test_pickle_complex_depends_class(pickler):
-    s = pickler.dumps(P4)
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_pickle_complex_depends_class(pickler, protocol):
+    s = pickler.dumps(P4, protocol=protocol)
     cls = pickler.loads(s)
     assert cls is P4
 
 
 @pytest.mark.parametrize('pickler', [cloudpickle, pickle], indirect=True)
-def test_pickle_complex_depends_instance(pickler):
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_pickle_complex_depends_instance(pickler, protocol):
     p = P4()
-    s = pickler.dumps(p)
+    s = pickler.dumps(p, protocol=protocol)
     inst = pickler.loads(s)
     assert eq(p, inst)
 
 
 @pytest.mark.skipif(cloudpickle is None, reason='cloudpickle not available')
-def test_issue_757():
+@pytest.mark.parametrize('protocol', [0, pickle.DEFAULT_PROTOCOL, pickle.HIGHEST_PROTOCOL])
+def test_issue_757(protocol):
     # https://github.com/holoviz/param/issues/759
     class P(param.Parameterized):
         a = param.Parameter()
 
     p = P()
-    s = cloudpickle.dumps(p)
+    s = cloudpickle.dumps(p, protocol=protocol)
     inst = cloudpickle.loads(s)
     assert eq(p, inst)