344: Added Param.__clone__() method; added corresponding unit tests

ipalib/frontend.py

@@ -117,6 +117,9 @@ def parse_param_spec(spec):
 
 
 class Param(plugable.ReadOnly):
+    """
+    A parameter accepted by a `Command`.
+    """
     __nones = (None, '', tuple(), [])
     __default = dict(
         doc='',
@@ -150,9 +153,18 @@ class Param(plugable.ReadOnly):
             allow_none=True
         )
         self.__normalize = self.__kw['normalize']
-        self.rules = (type_.validate,) + self.__kw['rules']
+        self.rules = self.__check_type(tuple, 'rules')
+        self.all_rules = (type_.validate,) + self.rules
         lock(self)
 
+    def __clone__(self, **override):
+        """
+        Return a new `Param` instance similar to this one.
+        """
+        kw = dict(self.__kw)
+        kw.update(override)
+        return self.__class__(self.name, self.type, **kw)
+
     def __check_type(self, type_, name, allow_none=False):
         value = self.__kw[name]
         return check_type(value, type_, name, allow_none)

ipalib/tests/test_frontend.py

@@ -147,7 +147,8 @@ class test_Param(ClassChecker):
         assert read_only(o, 'multivalue') is False
         assert read_only(o, 'default') is None
         assert read_only(o, 'default_from') is None
-        assert read_only(o, 'rules') == (type_.validate,)
+        assert read_only(o, 'rules') == tuple()
+        assert read_only(o, 'all_rules') == (type_.validate,)
 
         # Check default type_:
         o = self.cls(name)
@@ -173,6 +174,33 @@ class test_Param(ClassChecker):
         assert str(e) == \
             'Param.__init__() takes no such kwargs: another, whatever'
 
+    def test_clone(self):
+        """
+        Test the `frontend.Param.__clone__` method.
+        """
+        def compare(o, kw):
+            for (k, v) in kw.iteritems():
+                assert getattr(o, k) == v, (k, v, getattr(o, k))
+        default = dict(
+            required=False,
+            multivalue=False,
+            default=None,
+            default_from=None,
+            rules=tuple(),
+        )
+        name = 'hair_color?'
+        type_ = ipa_types.Int()
+        o = self.cls(name, type_)
+        compare(o, default)
+
+        override = dict(multivalue=True, default=42)
+        d = dict(default)
+        d.update(override)
+        clone = o.__clone__(**override)
+        assert clone.name == 'hair_color'
+        assert clone.type is o.type
+        compare(clone, d)
+
     def test_convert(self):
         """
         Test the `frontend.Param.convert` method.
@@ -277,7 +305,8 @@ class test_Param(ClassChecker):
 
         # Scenario 1: multivalue=False
         o = self.cls(name, type_, rules=my_rules)
-        assert o.rules == (type_.validate, case_rule)
+        assert o.rules == my_rules
+        assert o.all_rules == (type_.validate, case_rule)
         o.validate(okay)
         e = raises(errors.RuleError, o.validate, fail_case)
         assert e.name is name