Fix .abstract for classes named with leading underscore(s) (#439)

* Fix abstract class check for classes with leading underscore(s) in name (previously an declared abstract _Class would come back as not abstract).

* Add note about API0 and API1 test suites.

param/parameterized.py

@@ -2087,9 +2087,9 @@ def __is_abstract(mcs):
         # _ParameterizedMetaclass__abstract before running, but
         # the actual class object will have an attribute
         # _ClassName__abstract.  So, we have to mangle it ourselves at
-        # runtime.
+        # runtime. Mangling follows description in https://docs.python.org/2/tutorial/classes.html#private-variables-and-class-local-references
         try:
-            return getattr(mcs,'_%s__abstract'%mcs.__name__)
+            return getattr(mcs,'_%s__abstract'%mcs.__name__.lstrip("_"))
         except AttributeError:
             return False
 

tests/API0/testparameterizedobject.py

@@ -39,6 +39,10 @@ class AnotherTestPO(param.Parameterized):
 class TestAbstractPO(param.Parameterized):
     __abstract = True
 
+class _AnotherAbstractPO(param.Parameterized):
+    __abstract = True
+
+
 @nottest
 class TestParamInstantiation(AnotherTestPO):
     instPO = param.Parameter(default=AnotherTestPO(),instantiate=False)
@@ -118,6 +122,7 @@ def test_instantiation_inheritance(self):
     def test_abstract_class(self):
         """Check that a class declared abstract actually shows up as abstract."""
         self.assertEqual(TestAbstractPO.abstract,True)
+        self.assertEqual(_AnotherAbstractPO.abstract,True)
         self.assertEqual(TestPO.abstract,False)
 
 

tests/API1/testparameterizedobject.py

@@ -53,6 +53,9 @@ class AnotherTestPO(param.Parameterized):
 class TestAbstractPO(param.Parameterized):
     __abstract = True
 
+class _AnotherAbstractPO(param.Parameterized):
+    __abstract = True
+
 @nottest
 class TestParamInstantiation(AnotherTestPO):
     instPO = param.Parameter(default=AnotherTestPO(),instantiate=False)
@@ -140,6 +143,7 @@ def test_instantiation_inheritance(self):
     def test_abstract_class(self):
         """Check that a class declared abstract actually shows up as abstract."""
         self.assertEqual(TestAbstractPO.abstract,True)
+        self.assertEqual(_AnotherAbstractPO.abstract,True)
         self.assertEqual(TestPO.abstract,False)
 
 

tests/README.md

@@ -0,0 +1,13 @@
+In 2018, we moved most of `Parameterized` onto a `param` namespace
+object, expecting this to be the public API of param 2.0, and cleaning
+up the namespace of user classes.
+
+The new API has been in use for a while within holoviz projects, but
+we're still changing it. Meanwhile, the previous API remains
+available.
+
+The original API's tests were copied into an `API0` subdirectory,
+while tests in `API1` use the new API.
+
+(Probably not ideal to just copy everything, and cleaning up would be
+great, but this explains the two directories you see here.)