allow to set exported properties in code

Actually, only property values set in the configuration can
be exported, as values equal to the default are not exported.
For this, the mechanism of overwriting properties by class attributes
has to be modified.

Change-Id: I4388d1fbb36393e863556fbbc8df800dd4800c87
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/22161
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/properties.py

@@ -37,7 +37,7 @@ class Property:
     otherwise, this is optional in which case the default value is applied.
     All values MUST pass the datatype.
     '''
-    # note: this is inteded to be used on base classes.
+    # note: this is intended to be used on base classes.
     #       the VALUES of the properties are on the instances!
     def __init__(self, description, datatype, default=None, extname='', export=False, mandatory=None, settable=True):
         if not callable(datatype):
@@ -102,29 +102,24 @@ class PropertyMeta(type):
         for base in reversed(bases):
             properties.update(getattr(base, "properties", {}))
         # update with properties from new class
-        aprops = attrs.get('properties', {})
-        properties.update(aprops)
+        properties.update(attrs.get('properties', {}))
         newtype.properties = properties
 
         # generate getters
-        for k in properties:
+        for k, po in properties.items():
+
             def getter(self, pname=k):
                 val = self.__class__.properties[pname].default
                 return self.properties.get(pname, val)
+
             if k in attrs and not isinstance(attrs[k], property):
                 if callable(attrs[k]):
                     raise ProgrammingError('%r: property %r collides with method'
                                         % (newtype, k))
-                if k in aprops:
-                    # this property was defined in the same class
-                    raise ProgrammingError('%r: name collision with property %r'
-                                        % (newtype, k))
-                # assume the attribute value should be assigned to the property
+                # store the attribute value for putting on the instance later
                 try:
-                    # make a copy first!
-                    prop = Property(**newtype.properties[k].__dict__)
-                    prop.default = prop.datatype(attrs[k])
-                    newtype.properties[k] = prop
+                    # for inheritance reasons, it seems best to store it as a renamed attribute
+                    setattr(newtype, '_initProp_' + k, po.datatype(attrs[k]))
                 except BadValueError:
                     raise ProgrammingError('%r: property %r can not be set to %r'
                                             % (newtype, k, attrs[k]))
@@ -144,7 +139,10 @@ class HasProperties(metaclass=PropertyMeta):
         self.properties = {}
         # pre-init with properties default value (if any)
         for pn, po in self.__class__.properties.items():
-            if not po.mandatory:
+            value = getattr(self, '_initProp_' + pn, self)
+            if value is not self:  # property value was given as attribute
+                self.properties[pn] = value
+            elif not po.mandatory:
                 self.properties[pn] = po.default
 
     def checkProperties(self):

secop_psi/ppms.py

@@ -127,8 +127,6 @@ class Main(Communicator):
 class PpmsMixin(HasIodev, Module):
     properties = {
         'iodev': Attached(),
-        'general_stop': Property('respect general stop', datatype=BoolType(),
-                                 export=True, default=True)
     }
 
     pollerClass = Poller
@@ -439,6 +437,11 @@ class Temp(PpmsMixin, Drivable):
         14: [Status.ERROR, 'can not complete'],
         15: [Status.ERROR, 'general failure'],
     }
+    properties = {
+        'iodev': Attached(),
+        'general_stop': Property('respect general stop', datatype=BoolType(),
+                                 export=True, default=True)
+    }
 
     channel = 'temp'
     _stopped = False

test/test_properties.py

@@ -133,15 +133,6 @@ def test_Property_override():
                 pass
     assert 'collides with method' in str(e.value)
 
-    with pytest.raises(ProgrammingError) as e:
-        class cy(c): # pylint: disable=unused-variable
-            properties = {
-                'b' : Property('', FloatRange(), 3.14),
-            }
-            b = 1.5
-
-    assert 'name collision with property' in str(e.value)
-
     with pytest.raises(ProgrammingError) as e:
         class cz(c): # pylint: disable=unused-variable
             a = 's'