mod_python: txt format view of wiki pages throws exception

[Alec Thomas]

I'm not sure whether it's limited to mod_python however.

23:17:13 Trac[main] ERROR: Response already started
Traceback (most recent call last):
  File "/usr/lib/python2.4/site-packages/trac/web/main.py", line 283, in dispatch_request
    dispatcher.dispatch(req)
  File "/usr/lib/python2.4/site-packages/trac/web/main.py", line 176, in dispatch
    req.display(template, content_type or 'text/html')
  File "/usr/lib/python2.4/site-packages/trac/web/api.py", line 324, in display
    self.end_headers()
  File "/usr/lib/python2.4/site-packages/trac/web/api.py", line 244, in end_headers
    self._write = self._start_response(self._status, self._outheaders)
  File "/usr/lib/python2.4/site-packages/trac/web/wsgi.py", line 111, in _start_response
    assert not self.headers_set, 'Response already started'
AssertionError: Response already started

[Alec Thomas]

This is ​still present in r3047.

[Alec Thomas]

This doesn't occur with FCGI under lighttpd.

[Alec Thomas]

Actually, my last comment seems to not be 100% correct. I get an assertion failure under FCGI. The following patch fixes it:

trac/web/_fcgi.py

@@ -1188 +1188 @@
         result = None
 
         def write(data):
-            assert type(data) is str, 'write() argument must be string'
+            assert isinstance(data, basestring), 'write() argument must be string'
             assert headers_set, 'write() before start_response()'
 
             if not headers_sent:

[Matthew Good]

Alec, where was that called from? The Request.write method encodes unicode objects to the configured character set, so the data written to the FCGI response should be str objects. If something's writing unicode objects directly to the response it should be changed to encode them first.

[Alec Thomas]

Ah okay. This is probably one of the plugins I have installed then.

I'll close it and if I encounter it again I will reopen.

[Alec Thomas]

Yes, this was my own stupid fault. TracTags replaced the WikiModule but wasn't handling the return from the request handler correctly. Sorry about that.