added method to ParentsGroup to add a group easily (#624)

nornir/core/inventory.py

@@ -105,6 +105,18 @@ def __contains__(self, value: object) -> bool:
         else:
             return any([value == g for g in self])
 
+    def add(self, group: "Group") -> None:
+        """
+        Add the ParentGroup.  The group will only be appended
+        if it does not exist.
+
+        :param group: Parent Group object to add
+        :return: None
+        """
+        # only add the group if it doesn't exist
+        if not self.__contains__(group):
+            self.append(group)
+
 
 class InventoryElement(BaseAttributes):
     __slots__ = ("groups", "data", "connection_options")

tests/core/test_inventory.py

@@ -530,3 +530,50 @@ def test_get_hosts_dict(self, inv):
         assert "group_1" in dev1_groups
         assert dev2_paramiko_opts["username"] == "root"
         assert "dev3.group_2" in hosts_dict
+
+    def test_add_group_to_host_runtime(self):
+        orig_data = {"var1": "val1"}
+        data = {"var3": "val3"}
+        g1 = inventory.Group(name="g1", data=orig_data)
+        g2 = inventory.Group(name="g2", groups=inventory.ParentGroups([g1]))
+        g3 = inventory.Group(name="g3", groups=inventory.ParentGroups([g2]), data=data)
+        h1 = inventory.Host(name="h1", groups=inventory.ParentGroups([g1, g2]))
+        h2 = inventory.Host(name="h2")
+        hosts = {"h1": h1, "h2": h2}
+        groups = {"g1": g1, "g2": g2}
+        inv = inventory.Inventory(hosts=hosts, groups=groups)
+
+        assert "h1" in inv.hosts
+        assert g3 not in inv.hosts["h1"].groups
+        assert h1.get("var3", None) is None
+
+        h1.groups.add(g3)
+        assert g3 in h1.groups
+        assert h1.get("var3", None) == "val3"
+
+    def test_remove_group_from_host(self):
+        data = {"var3": "val3"}
+        orig_data = {"var1": "val1"}
+        g1 = inventory.Group(name="g1", data=orig_data)
+        g2 = inventory.Group(name="g2", groups=inventory.ParentGroups([g1]))
+        g3 = inventory.Group(name="g3", groups=inventory.ParentGroups([g2]), data=data)
+        h1 = inventory.Host(name="h1", groups=inventory.ParentGroups([g1, g2, g3]))
+        h2 = inventory.Host(name="h2")
+        hosts = {"h1": h1, "h2": h2}
+        groups = {"g1": g1, "g2": g2}
+        inv = inventory.Inventory(hosts=hosts, groups=groups)
+
+        assert "h1" in inv.hosts
+        assert g3 in inv.hosts["h1"].groups
+        assert h1.get("var3") == "val3"
+
+        g3.data["var3"] = "newval3"
+        assert h1.get("var3", None) == "newval3"
+
+        h1.groups.remove(g3)
+        assert g3 not in h1.groups
+        assert h1.get("var3", None) is None
+        assert h1.get("var1", None) == "val1"
+
+        with pytest.raises(ValueError):
+            h1.groups.remove(g3)