From 02507f9b08239a28f464c1009c594c84482a662c Mon Sep 17 00:00:00 2001
From: Matt Prahl <mprahl@redhat.com>
Date: Feb 09 2017 20:03:09 +0000
Subject: Have xmd default as an empty dictionary


---

diff --git a/modulemd/__init__.py b/modulemd/__init__.py
index 1b25f66..9fc79f9 100644
--- a/modulemd/__init__.py
+++ b/modulemd/__init__.py
@@ -75,7 +75,7 @@ class ModuleMetadata(object):
         self.community = ""
         self.documentation = ""
         self.tracker = ""
-        self.xmd = None
+        self.xmd = dict()
         self.profiles = dict()
         self.api = ModuleAPI()
         self.filter = ModuleFilter()
@@ -630,7 +630,7 @@ class ModuleMetadata(object):
 
     @xmd.setter
     def xmd(self, d):
-        if d is not None and not isinstance(d, dict):
+        if not isinstance(d, dict):
             raise TypeError("xmd: data type not supported")
         self._xmd = d
 
diff --git a/modulemd/tests/io.py b/modulemd/tests/io.py
index cee9644..5f73b1e 100644
--- a/modulemd/tests/io.py
+++ b/modulemd/tests/io.py
@@ -51,7 +51,7 @@ class TestIO(unittest.TestCase):
         self.assertSetEqual(self.mmd.module_licenses, set(["MIT"]))
         self.assertSetEqual(self.mmd.content_licenses,
                 set(["Beerware", "GPLv2+", "zlib"]))
-        self.assertIsNone(self.mmd.xmd)
+        self.assertEqual(self.mmd.xmd, {'some_key': 'some_data'})
         self.assertDictEqual(self.mmd.buildrequires,
                 {
                     "generational-core" : "and-its-stream-name",
diff --git a/spec.yaml b/spec.yaml
index e6d05ce..bce4314 100644
--- a/spec.yaml
+++ b/spec.yaml
@@ -38,9 +38,10 @@ data:
             - GPLv2+
             - zlib
     # Extensible metadata block
-    # A dictionary of user-defined keys and values.  May be null.
-    # Optional.  Defaults to null.
-    xmd: ~
+    # A dictionary of user-defined keys and values.
+    # Optional.  Defaults to an empty dictionary.
+    xmd:
+      some_key: some_data
     # Module dependencies, if any.  Optional.
     # TODO: Provides, conflicts, obsoletes, recommends, etc.
     # TODO: Stream name globbing or regular expression support