Load tab context data during init for "preload" tabs. Fixes bug 959800.

Change-Id: If05c022def2e97bbae682db65d4311b1401e850d

1 files changed, 11 insertions, 1 deletions

diff --git a/horizon/tabs/base.py b/horizon/tabs/base.py
index 17a5a535a..12ade1986 100644
--- a/horizon/tabs/base.py
+++ b/horizon/tabs/base.py
@@ -95,6 +95,10 @@ class TabGroup(html.HTMLElement):
         self._tabs = SortedDict(tab_instances)
         if not self._set_active_tab():
             self.tabs_not_available()
+        # Preload all data that will be loaded to allow errors to be displayed
+        for tab in self._tabs.values():
+            if tab.load:
+                tab._context_data = tab.get_context_data(request)
 
     def __repr__(self):
         return "<%s: %s>" % (self.__class__.__name__, self.slug)
@@ -249,6 +253,12 @@ class Tab(html.HTMLElement):
         load_preloaded = self.preload or self.is_active()
         return load_preloaded and self._allowed and self._enabled
 
+    @property
+    def context_data(self):
+        if not getattr(self, "_context_data", None):
+            self._context_data = self.get_context_data(self.request)
+        return self._context_data
+
     def render(self):
         """
         Renders the tab to HTML using the :meth:`~horizon.tabs.Tab.get_data`
@@ -263,7 +273,7 @@ class Tab(html.HTMLElement):
         if not self.load:
             return ''
         try:
-            context = self.get_context_data(self.request)
+            context = self.context_data
         except exceptions.Http302:
             raise
         except: