Refactor get_ec2_userdata to return list

This makes it easier to override the userdata in other modules. This
means that bootstrap salt can extend the userdata without having to
decode the mime message and re-mime it afterwards.

bootstrap_cfn/config.py

@@ -551,7 +551,7 @@ def get_ec2_userdata(self):
             })
 
         if len(parts):
-            return mime_packer.pack(parts)
+            return parts
 
     HOSTNAME_BOOTHOOK_TEMPLATE = textwrap.dedent("""\
     #!/bin/sh
@@ -654,8 +654,10 @@ def ec2(self):
             ImageId=FindInMap("AWSRegion2AMI", Ref("AWS::Region"), "AMI"),
             BlockDeviceMappings=devices,
         )
+
         user_data = self.get_ec2_userdata()
         if user_data:
+            user_data = mime_packer.pack(user_data)
             launch_config.UserData = Base64(user_data)
 
         resources.append(launch_config)

tests/test_mime_packer.py

@@ -0,0 +1,36 @@
+import email
+
+import unittest
+
+from testfixtures import compare
+
+from bootstrap_cfn import mime_packer
+
+
+class TestMimePacker(unittest.TestCase):
+
+    def setUp(self):
+        self.parts = []
+        self.parts.append({
+            'content': 'MORESTRING',
+            'mime_type': 'text/cloud-boothook'
+        })
+        self.parts.append({
+            'content': 'SOMESTRING',
+            'mime_type': 'text/cloud-config'
+        })
+
+    def test_encode(self):
+        ret = mime_packer.pack(self.parts)
+        self.assertTrue('SOMESTRING' in ret)
+        self.assertTrue('MORESTRING' in ret)
+
+    def test_decode(self):
+        ret = mime_packer.pack(self.parts)
+        parts = [part for part in email.message_from_string(ret).walk()]
+        compare(
+            [part.get_content_type() for part in parts],
+            ["multipart/mixed", "text/cloud-boothook", "text/cloud-config"],
+            prefix="mimeparts are in expected order")
+        compare(parts[1].get_payload(), "MORESTRING")
+        compare(parts[2].get_payload(), "SOMESTRING")

tests/tests.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python
-import email
 import json
 import unittest
 from StringIO import StringIO
@@ -18,6 +17,7 @@
 import yaml
 
 from bootstrap_cfn import errors
+from bootstrap_cfn import mime_packer
 from bootstrap_cfn.config import ConfigParser, ProjectConfig
 
 
@@ -1047,14 +1047,14 @@ def test_launchconfig_userdata(self):
             IamInstanceProfile=Ref("InstanceProfile"),
             InstanceType="t2.micro",
             AssociatePublicIpAddress="true",
-            UserData=Base64("Mock Userdata String"),
+            UserData=Base64("Mock String"),
         )
 
-        with patch.object(config, "get_ec2_userdata", return_value="Mock Userdata String"):
-            ec2_json = self._resources_to_dict(config.ec2())
-            expected = self._resources_to_dict([BaseHostLaunchConfig])
-            compare(ec2_json['BaseHostLaunchConfig'], expected['BaseHostLaunchConfig'])
-            pass
+        with patch.object(config, "get_ec2_userdata", return_value="Mock String"):
+            with patch.object(mime_packer, "pack", side_effect=lambda x: x):
+                ec2_json = self._resources_to_dict(config.ec2())
+                expected = self._resources_to_dict([BaseHostLaunchConfig])
+                compare(ec2_json['BaseHostLaunchConfig'], expected['BaseHostLaunchConfig'])
 
     def test_get_ec2_userdata(self):
         data = {
@@ -1063,24 +1063,10 @@ def test_get_ec2_userdata(self):
             }
         }
         config = ConfigParser(data, environment="env", application="test", stack_name="my-stack")
-
         with patch.object(config, 'get_hostname_boothook', return_value={"content": "sentinel"}) as mock_boothook:
-            # This test is slightly silly as we are testing the decoding with
-            # the same code as the generator... but it's that or we test it
-            # with regexp.
-            mime_text = config.get_ec2_userdata()
-
+            compare(yaml.load(config.get_ec2_userdata()[1]['content']), data['ec2']['cloud_config'])
             mock_boothook.assert_called_once_with(data['ec2'])
-
-            parts = [part for part in email.message_from_string(mime_text).walk()]
-
-            compare(
-                [part.get_content_type() for part in parts],
-                ["multipart/mixed", "text/plain", "text/cloud-config"],
-                prefix="Userdata parts are in expected order")
-
-            compare(parts[1].get_payload(), "sentinel")
-            compare(yaml.load(parts[2].get_payload()), data['ec2']['cloud_config'])
+            compare(config.get_ec2_userdata()[0]['content'], 'sentinel')
 
     def test_get_hostname_boothook(self):
         config = ConfigParser({}, environment="env", application="test", stack_name="my-stack")