Handle failures on column filters more gracefully

With certain inputs it's possible for filters to fail, however we
should still display the table as well as return the data we have even
if it didn't go through one filter successfully.

We're still expecting "filters" to be made of functions, therefore the
func_name attribute should exist.

Note that this warning message being displayed still indicates that
there is a programming error somewhere that should be fixed.

Related-Bug: #1286959
Change-Id: I408dc9fbdaa7dfe49a39ad3a96a0e1256f6a99eb

horizon/tables/base.py

@@ -347,7 +347,14 @@ class Column(html.HTMLElement):
             data = display_value[0]
         else:
             for filter_func in self.filters:
-                data = filter_func(data)
+                try:
+                    data = filter_func(data)
+                except Exception:
+                    msg = ("Filter '%(filter)s' failed with data "
+                           "'%(data)s' on column '%(col_name)s'")
+                    LOG.warning(msg, {'filter': filter_func.func_name,
+                                      'data': data,
+                                      'col_name': unicode(self.verbose_name)})
 
         if data and self.truncate:
             data = truncatechars(data, self.truncate)

horizon/test/tests/tables.py

@@ -18,6 +18,7 @@ from django.core.urlresolvers import reverse
 from django import forms
 from django import http
 from django import shortcuts
+from django.template import defaultfilters
 
 from mox import IsA  # noqa
 
@@ -1091,6 +1092,19 @@ class DataTableTests(test.TestCase):
         row = self.table.get_rows()[0]
         self.assertTrue("down" in row.cells['status'].value)
 
+    def test_broken_filter(self):
+        class MyTableBrokenFilter(MyTable):
+            value = tables.Column('value',
+                                  filters=(defaultfilters.timesince,))
+
+        value = "not_a_date"
+        data = TEST_DATA[0]
+        data.value = value
+
+        table = MyTableBrokenFilter(self.request, [data])
+        resp = http.HttpResponse(table.render())
+        self.assertContains(resp, value)
+
 
 class SingleTableView(table_views.DataTableView):
     table_class = MyTable