get_display_name(): Don't attempt to concatenate variant information to None

Fixes #601

2 files changed, 11 insertions, 1 deletions

diff --git a/babel/core.py b/babel/core.py
index d028c07..211849b 100644
--- a/babel/core.py
+++ b/babel/core.py
@@ -379,7 +379,7 @@ class Locale(object):
             locale = self
         locale = Locale.parse(locale)
         retval = locale.languages.get(self.language)
-        if self.territory or self.script or self.variant:
+        if retval and (self.territory or self.script or self.variant):
             details = []
             if self.script:
                 details.append(locale.scripts.get(self.script))
diff --git a/tests/test_core.py b/tests/test_core.py
index f22ab30..fc637d2 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -317,3 +317,13 @@ def test_compatible_classes_in_global_and_localedata(filename):
 
     with open(filename, 'rb') as f:
         return Unpickler(f).load()
+
+
+def test_issue_601_no_language_name_but_has_variant():
+    # kw_GB has a variant for Finnish but no actual language name for Finnish,
+    # so `get_display_name()` previously crashed with a TypeError as it attempted
+    # to concatenate " (Finnish)" to None.
+    # Instead, it's better to return None altogether, as we can't reliably format
+    # part of a language name.
+
+    assert Locale.parse('fi_FI').get_display_name('kw_GB') == None