Create a context manager that prevents updating of the search index

Given a model that has non-searchable fields that are updated often, this
context manager can prevent frivolous search index updates.

src/watson/__init__.py

@@ -27,3 +27,4 @@ get_adapter = default_search_engine.get_adapter
 
 # Easy context management.
 update_index = search_context_manager.update_index
+skip_index_update = search_context_manager.skip_index_update

src/watson/registration.py

@@ -232,7 +232,15 @@ class SearchContextManager(local):
         The returned context manager can also be used as a decorator.
         """
         return SearchContext(self)
-    
+
+    def skip_index_update(self):
+        """
+        Marks up a block of code as not requiring a search index update.
+
+        Like update_index, the returned context manager can also be used as a decorator.
+        """
+        return SkipSearchContext(self)
+
     # Signalling hooks.
         
     def _request_finished_receiver(self, **kwargs):
@@ -281,8 +289,21 @@ class SearchContext(object):
                 if not exception:
                     self.__exit__(None, None, None)
         return do_search_context
-        
-            
+
+
+class SkipSearchContext(SearchContext):
+
+    """A context that skips over index updating"""
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        """Mark it as invalid and exit"""
+        try:
+            self._context_manager.invalidate()
+        finally:
+            self._context_manager.end()
+
+
+
 # The shared, thread-safe search context manager.
 search_context_manager = SearchContextManager()
 

src/watson/tests.py

@@ -244,6 +244,13 @@ class InternalsTest(SearchTestBase):
         # Test a search that should get not model.
         self.assertEqual(watson.search("fooo").count(), 0)
         
+    def testSkipSearchIndexUpdate(self):
+        with watson.skip_index_update():
+            self.test11.title = "fooo"
+            self.test11.save()
+        # Test a search that should get not model.
+        self.assertEqual(watson.search("fooo").count(), 0)
+        
     def testFixesDuplicateSearchEntries(self):
         search_entries = SearchEntry.objects.filter(engine_slug="default")
         # Duplicate a couple of search entries.