Adding support for default values in FindInMap

tests/test_findinmap.py

@@ -0,0 +1,37 @@
+import unittest
+
+from troposphere import BaseAWSObject, FindInMap
+
+expected_find_in_map = {"Fn::FindInMap": ["m", "t", "s"]}
+
+expected_find_in_map_with_default = {
+    "Fn::FindInMap": ["m", "t", "s", {"DefaultValue": "d"}]
+}
+
+map_object = BaseAWSObject(title="m")
+
+
+class TestFindInMap(unittest.TestCase):
+    def test_find_in_map(self):
+        find_in_map = FindInMap(mapname="m", toplevelkey="t", secondlevelkey="s")
+        self.assertEqual(find_in_map.to_dict(), expected_find_in_map)
+
+    def test_find_in_map_with_object(self):
+        find_in_map = FindInMap(mapname=map_object, toplevelkey="t", secondlevelkey="s")
+        self.assertEqual(find_in_map.to_dict(), expected_find_in_map)
+
+    def test_find_in_map_with_default(self):
+        find_in_map = FindInMap(
+            mapname="m", toplevelkey="t", secondlevelkey="s", defaultvalue="d"
+        )
+        self.assertEqual(find_in_map.to_dict(), expected_find_in_map_with_default)
+
+    def test_find_in_map_with_object_and_default(self):
+        find_in_map = FindInMap(
+            mapname=map_object, toplevelkey="t", secondlevelkey="s", defaultvalue="d"
+        )
+        self.assertEqual(find_in_map.to_dict(), expected_find_in_map_with_default)
+
+
+if __name__ == "__main__":
+    unittest.main()

troposphere/__init__.py

@@ -537,11 +537,18 @@ def __init__(self, data: Any) -> None:
 
 class FindInMap(AWSHelperFn):
     def __init__(
-        self, mapname: object, toplevelkey: object, secondlevelkey: object
+        self,
+        mapname: object,
+        toplevelkey: object,
+        secondlevelkey: object,
+        defaultvalue: Optional[object] = None,
     ) -> None:
-        self.data = {
-            "Fn::FindInMap": [self.getdata(mapname), toplevelkey, secondlevelkey]
-        }
+        find_in_map_details = [self.getdata(mapname), toplevelkey, secondlevelkey]
+
+        if defaultvalue is not None:
+            find_in_map_details.append({"DefaultValue": defaultvalue})
+
+        self.data = {"Fn::FindInMap": find_in_map_details}
 
 
 class GetAtt(AWSHelperFn):