Allow for AWSHelperFn objects in Tags

tests/test_tags.py

@@ -1,5 +1,5 @@
 import unittest
-from troposphere import Sub, Tags
+from troposphere import If, Sub, Tag, Tags
 from troposphere.autoscaling import Tags as ASTags
 
 
@@ -15,6 +15,19 @@ def test_TagAddition(self):
         ]
         self.assertEqual(tags.to_dict(), result)
 
+    def test_TagConditional(self):
+        tags = Tags(
+            {'foo': 'foo'},
+            If('MyCondition', Tag('bar', 'bar'), Tag('baz', 'baz'))
+        )
+        result = [
+            {"Fn::If": ["MyCondition",
+                        {"Key": "bar", "Value": "bar"},
+                        {"Key": "baz", "Value": "baz"}]},
+            {'Value': 'foo', 'Key': 'foo'},
+        ]
+        self.assertEqual(tags.to_dict(), result)
+
     def test_ASTagAddition(self):
         tags = ASTags(foo=('fooval', True))
         tags += ASTags(bar=('barval', False))

troposphere/__init__.py

@@ -525,25 +525,33 @@ def __init__(self, data):
         self.data = {'Fn::ImportValue': data}
 
 
+class Tag(AWSHelperFn):
+    def __init__(self, k, v):
+        self.data = {'Key': k, 'Value': v, }
+
+
 class Tags(AWSHelperFn):
     def __init__(self, *args, **kwargs):
+        self.tags = []
         if not args:
             # Assume kwargs variant
             tag_dict = kwargs
         else:
-            if len(args) != 1:
-                raise(TypeError, "Multiple non-kwargs passed to Tags")
-
-            # Validate single argument passed in is a dict
-            if not isinstance(args[0], dict):
-                raise(TypeError, "Tags needs to be either kwargs or dict")
-            tag_dict = args[0]
+            tag_dict = {}
+            for arg in args:
+                # Validate argument passed in is an AWSHelperFn or...
+                if isinstance(arg, AWSHelperFn):
+                    self.tags.append(arg)
+                # Validate argument passed in is a dict
+                elif isinstance(arg, dict):
+                    tag_dict.update(arg)
+                else:
+                    raise(TypeError, "Tags needs to be either kwargs, "
+                                     "dict, or AWSHelperFn")
 
         def add_tag(tag_list, k, v):
             tag_list.append({'Key': k, 'Value': v, })
 
-        self.tags = []
-
         # Detect and handle non-string Tag items which do not sort in Python3
         if all(isinstance(k, basestring) for k in tag_dict):
             for k, v in sorted(tag_dict.items()):