AttributeCollection: No longer allows duplicate overriding attributes

Previously if parameters with the same names and override set to True
were added to an extension at the same level one would silently
override the other.

This is no longer the case and an error will be show instead.

Also added tests to check that this is handeled correctly

wlauto/core/extension.py

@@ -82,7 +82,12 @@ class AttributeCollection(object):
         return p
 
     def __iadd__(self, other):
+        other = [self._to_attrcls(p) for p in other]
+        names = []
         for p in other:
+            if p.name in names:
+                raise ValueError("Duplicate '{}' {}".format(p.name, p.__class__.__name__.split('.')[-1]))
+            names.append(p.name)
             self.add(p)
         return self
 
@@ -687,4 +692,3 @@ class Module(Extension):
 
     def initialize(self, context):
         pass
-

wlauto/tests/test_extension.py

@@ -320,6 +320,13 @@ class ParametersTest(TestCase):
         myext = _instantiate(MyOtherExtension, mandatory=1, optional='invalid')
         myext.validate()
 
+    @raises(ValueError)
+    def test_duplicate_param_override(self):
+        class DuplicateParamExtension(MyBaseExtension):  # pylint: disable=W0612
+            parameters = [
+                Parameter('food', override=True, default='cheese'),
+                Parameter('food', override=True, default='cheese'),
+            ]
 
 class ModuleTest(TestCase):
 
@@ -340,4 +347,3 @@ class ModuleTest(TestCase):
 def _instantiate(cls, *args, **kwargs):
     # Needed to get around Extension's __init__ checks
     return cls(*args, **kwargs)
-