pygi-property: Lookup property in base classes of non-introspected types

Look for introspection data in the base classes of non-introspected gtypes.
This is necessary to look up introspection data for plugins.

https://bugzilla.gnome.org/show_bug.cgi?id=684058

gi/pygi-property.c

@@ -54,27 +54,27 @@ _pygi_lookup_property_from_g_type (GType g_type, const gchar *attr_name)
 
     repository = g_irepository_get_default();
     info = g_irepository_find_by_gtype (repository, g_type);
-    if (info == NULL) {
-        return NULL;
-    }
+    if (info != NULL) {
 
-    n_infos = g_object_info_get_n_properties ( (GIObjectInfo *) info);
-    for (i = 0; i < n_infos; i++) {
-        GIPropertyInfo *property_info;
+        n_infos = g_object_info_get_n_properties ( (GIObjectInfo *) info);
+        for (i = 0; i < n_infos; i++) {
+            GIPropertyInfo *property_info;
 
-        property_info = g_object_info_get_property ( (GIObjectInfo *) info, i);
-        g_assert (info != NULL);
+            property_info = g_object_info_get_property ( (GIObjectInfo *) info,
+                                                         i);
+            g_assert (info != NULL);
 
-        if (strcmp (attr_name, g_base_info_get_name (property_info)) == 0) {
-            g_base_info_unref (info);
-            return property_info;
+            if (strcmp (attr_name, g_base_info_get_name (property_info)) == 0) {
+                g_base_info_unref (info);
+                return property_info;
+            }
+
+            g_base_info_unref (property_info);
         }
 
-        g_base_info_unref (property_info);
+        g_base_info_unref (info);
     }
 
-    g_base_info_unref (info);
-
     parent = g_type_parent (g_type);
     if (parent > 0)
         return _pygi_lookup_property_from_g_type (parent, attr_name);

tests/test_everything.py

@@ -596,6 +596,18 @@ class TestProperties(unittest.TestCase):
         object_.props.gtype = str
         self.assertEqual(object_.props.gtype, GObject.TYPE_STRING)
 
+    def test_parent_class(self):
+        class A(Everything.TestObj):
+            prop1 = GObject.Property(type=int)
+
+        a = A()
+        a.props.int = 20
+        self.assertEqual(a.props.int, 20)
+
+        # test parent property which needs introspection
+        a.props.list = ("str1", "str2")
+        self.assertEqual(a.props.list, ["str1", "str2"])
+
 
 class TestTortureProfile(unittest.TestCase):
     def test_torture_profile(self):