Update of callbacks dict in RequestDispatcher.dispatch makes it difficult to write test case

[Ryan J Ollos]

For example I've written some test case like ​browser:trachacksplugin/trunk/trachacks/tests/web_ui.py@15127:109#L104, but when I try to use MockRequest the tests don't pass because the callbacks are overwritten: tags/trac-1.2/trac/web/main.py@:195-206#L184​.

I can make the tests work with the following change:

trac/web/main.py

@@ -192 +192 @@
         chrome = Chrome(self.env)
 
         # Setup request callbacks for lazily-evaluated properties
-        req.callbacks.update({
+        default_callbacks = {
             'authname': self.authenticate,
             'chrome': chrome.prepare_request,
             'form_token': self._get_form_token,
@@ -203 +203 @@
             'tz': self._get_timezone,
             'use_xsendfile': self._get_use_xsendfile,
             'xsendfile_header': self._get_xsendfile_header,
-        })
+        }
+        for key, value in default_callbacks.iteritems():
+            req.callbacks.setdefault(key, value)
 
         try:
             # Select the component that should handle the request

Does anyone foresee any negative side effects?