fix command inheritance

Command.ownProperties must be definead in __init__

+ add test for this

Change-Id: I283331be6439a49ec61d28f04869a5b44704236f
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/27104
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

test/test_params.py

@@ -103,3 +103,30 @@ def test_Export():
     class Mod(HasAccessibles):
         param = Parameter('description1', datatype=BoolType, default=False)
     assert Mod.param.export == '_param'
+
+
+def test_Command_Inheritance():
+    class Base(HasAccessibles):
+        @Command(BoolType(), visibility=2)
+        def cmd(self, arg):
+            """first"""
+
+    class Sub(Base):
+        @Command(group='grp')
+        def cmd(self, arg):
+            """second"""
+
+    class Sub2(Base):
+        @Command(FloatRange())
+        def cmd(self, arg):
+            """third"""
+
+    assert Sub.accessibles['cmd'].for_export() == {
+        'description': 'second', 'group': 'grp', 'visibility': 2,
+        'datainfo': {'type': 'command', 'argument': {'type': 'bool'}}
+    }
+
+    assert Sub2.accessibles['cmd'].for_export() == {
+        'description': 'third', 'visibility': 2,
+        'datainfo': {'type': 'command', 'argument': {'type': 'double'}}
+    }