Don't show course start date if it hasn't been set.

If neither start nor advertised_start has been changed from default
don't show the course start date.

This allows us to accept course registrations for courses whose start
date is yet TBD.

common/lib/xmodule/xmodule/course_module.py

@@ -821,6 +821,10 @@ class CourseDescriptor(CourseFields, SequenceDescriptor):
 
     @property
     def start_date_text(self):
+        """
+        Returns the desired text corresponding the course's start date.  Prefers .advertised_start,
+        then falls back to .start
+        """
         def try_parse_iso_8601(text):
             try:
                 result = Date().from_json(text)
@@ -835,12 +839,22 @@ class CourseDescriptor(CourseFields, SequenceDescriptor):
 
         if isinstance(self.advertised_start, basestring):
             return try_parse_iso_8601(self.advertised_start)
-        elif self.advertised_start is None and self.start is None:
-            # TODO this is an impossible state since the init function forces start to have a value
-            return 'TBD'
+        elif self.start_date_is_still_default:
+            _ = self.runtime.service(self, "i18n").ugettext
+            # Translators: TBD stands for 'To Be Determined' and is used when a course
+            # does not yet have an announced start date.
+            return _('TBD')
         else:
             return (self.advertised_start or self.start).strftime("%b %d, %Y")
 
+    @property
+    def start_date_is_still_default(self):
+        """
+        Checks if the start date set for the course is still default, i.e. .start has not been modified,
+        and .advertised_start has not been set.
+        """
+        return self.advertised_start is None and self.start == CourseFields.start.default
+
     @property
     def end_date_text(self):
         """

common/lib/xmodule/xmodule/tests/test_course_module.py

@@ -134,23 +134,29 @@ class IsNewCourseTestCase(unittest.TestCase):
             print "Comparing %s to %s" % (a, b)
             assertion(a_score, b_score)
 
+    start_advertised_settings = [
+        # start, advertised, result, is_still_default
+        ('2012-12-02T12:00', None, 'Dec 02, 2012', False),
+        ('2012-12-02T12:00', '2011-11-01T12:00', 'Nov 01, 2011', False),
+        ('2012-12-02T12:00', 'Spring 2012', 'Spring 2012', False),
+        ('2012-12-02T12:00', 'November, 2011', 'November, 2011', False),
+        (xmodule.course_module.CourseFields.start.default, None, 'TBD', True),
+        (xmodule.course_module.CourseFields.start.default, 'January 2014', 'January 2014', False),
+    ]
+
     @patch('xmodule.course_module.datetime.now')
     def test_start_date_text(self, gmtime_mock):
         gmtime_mock.return_value = NOW
-
-        settings = [
-            # start, advertized, result
-            ('2012-12-02T12:00', None, 'Dec 02, 2012'),
-            ('2012-12-02T12:00', '2011-11-01T12:00', 'Nov 01, 2011'),
-            ('2012-12-02T12:00', 'Spring 2012', 'Spring 2012'),
-            ('2012-12-02T12:00', 'November, 2011', 'November, 2011'),
-        ]
-
-        for s in settings:
+        for s in self.start_advertised_settings:
             d = get_dummy_course(start=s[0], advertised_start=s[1])
             print "Checking start=%s advertised=%s" % (s[0], s[1])
             self.assertEqual(d.start_date_text, s[2])
 
+    def test_start_date_is_default(self):
+        for s in self.start_advertised_settings:
+            d = get_dummy_course(start=s[0], advertised_start=s[1])
+            self.assertEqual(d.start_date_is_still_default, s[3])
+
     def test_display_organization(self):
         descriptor = get_dummy_course(start='2012-12-02T12:00', is_new=True)
         self.assertNotEqual(descriptor.location.org, descriptor.display_org_with_default)