Allow theme template block override

common/djangoapps/edxmako/paths.py

@@ -70,6 +70,11 @@ class DynamicTemplateLookup(TemplateLookup):
             try:
                 # Try to find themed template, i.e. see if current theme overrides the template
                 template = super(DynamicTemplateLookup, self).get_template(get_template_path_with_theme(uri))
+                # For an overriding template, the uri is the path to the same template, so the lookup always
+                # finds the same overriding template. If that's the case, route to exception so that the
+                # uri can be stripped of the path and the parent template can be found.
+                if template == super(DynamicTemplateLookup, self).get_template(uri):
+                    raise TopLevelLookupException()
             except TopLevelLookupException:
                 # strip off the prefix path to theme and look in default template dirs
                 template = super(DynamicTemplateLookup, self).get_template(strip_site_theme_templates_path(uri))

common/test/test-theme/lms/templates/dashboard.html

+<%inherit file="dashboard.html" />
+<%block name="pagetitle">Overridden Title!</%block>
+${parent.body()}
+<%block name="bodyextra">Overriden Body Extra!</%block>

openedx/core/djangoapps/theming/tests/test_theme_style_overrides.py

@@ -64,6 +64,30 @@ class TestComprehensiveThemeLMS(TestCase):
         result = staticfiles.finders.find('test-theme/images/logo.png')
         self.assertEqual(result, settings.TEST_THEME / 'lms/static/images/logo.png')
 
+    @with_comprehensive_theme("test-theme")
+    def test_override_block_in_parent(self):
+        """
+        Test that theme title is used instead of parent title.
+        """
+        self._login()
+        dashboard_url = reverse('dashboard')
+        resp = self.client.get(dashboard_url)
+        self.assertEqual(resp.status_code, 200)
+        # This string comes from the 'pagetitle' block of the overriding theme.
+        self.assertContains(resp, "Overridden Title!")
+
+    @with_comprehensive_theme("test-theme")
+    def test_override_block_in_grandparent(self):
+        """
+        Test that theme title is used instead of parent's parent's title.
+        """
+        self._login()
+        dashboard_url = reverse('dashboard')
+        resp = self.client.get(dashboard_url)
+        self.assertEqual(resp.status_code, 200)
+        # This string comes from the 'bodyextra' block of the overriding theme.
+        self.assertContains(resp, "Overriden Body Extra!")
+
 
 @skip_unless_cms
 class TestComprehensiveThemeCMS(TestCase):