TypeError raised when rendering error with chunked encoding

[Jun Omae]

I get the following error while investigating #13038 with [trac] use_chunked_encoding = enabled.

Exception happened during processing of request from ('192.168.11.29', 50776)
Traceback (most recent call last):
  File "/usr/lib/python2.7/SocketServer.py", line 596, in process_request_thread
    self.finish_request(request, client_address)
  File "/usr/lib/python2.7/SocketServer.py", line 331, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/usr/lib/python2.7/SocketServer.py", line 652, in __init__
    self.handle()
  File "/usr/lib/python2.7/BaseHTTPServer.py", line 340, in handle
    self.handle_one_request()
  File "/home/jun66j5/src/tracdev/git/trac/web/wsgi.py", line 212, in handle_one_request
    gateway.run(self.server.application)
  File "/home/jun66j5/src/tracdev/git/trac/web/wsgi.py", line 112, in run
    response = application(self.environ, self._start_response)
  File "trac/web/standalone.py", line 63, in __call__
    return self.application(environ, start_response)
  File "trac/web/standalone.py", line 94, in __call__
    return self.application(environ, start_response)
  File "/home/jun66j5/src/tracdev/git/trac/web/main.py", line 632, in dispatch_request
    return _dispatch_request(req, env, env_error)
  File "/home/jun66j5/venv/py27/local/lib/python2.7/site-packages/memory_profiler.py", line 1072, in wrapper
    val = prof(func)(*args, **kwargs)
  File "/home/jun66j5/venv/py27/local/lib/python2.7/site-packages/memory_profiler.py", line 659, in f
    return func(*args, **kwds)
  File "/home/jun66j5/src/tracdev/git/trac/web/main.py", line 672, in _dispatch_request
    _send_user_error(req, env, e)
  File "/home/jun66j5/src/tracdev/git/trac/web/main.py", line 692, in _send_user_error
    req.send_error(sys.exc_info(), status=e.code, env=env, data=data)
  File "/home/jun66j5/src/tracdev/git/trac/web/api.py", line 842, in send_error
    self.send_header('Content-Length', len(out))
TypeError: object of type 'generator' has no len()

We should ignore [trac] use_chunked_encoding option when rendering the error (untested patch).

trac/web/api.py

@@ -813 +813 @@
                 if env:
                     from trac.web.chrome import Chrome, add_stylesheet
                     add_stylesheet(self, 'common/css/code.css')
-                    metadata = {'content_type': 'text/html'}
+                    metadata = {'content_type': 'text/html',
+                                'iterable': False}
                     try:
                         out = Chrome(env).render_template(self, template, data,
                                                           metadata)

[Ryan J Ollos]

Your patch resolves the issue per my testing. Alternatively, would the following be valid?:

trac/web/api.py

@@ -839 +839 @@
         self.send_header('Cache-Control', 'must-revalidate')
         self.send_header('Expires', 'Fri, 01 Jan 1999 00:00:00 GMT')
         self.send_header('Content-Type', content_type + ';charset=utf-8')
-        self.send_header('Content-Length', len(out))
+        if isinstance(out, basestring):
+            self.send_header('Content-Length', len(out))
         self._send_configurable_headers()
         self._send_cookie_headers()

Though I suppose the error page doesn't need to be rendered in chunks because it's a fairly small amount of content.

I did some refactoring in rjollos.git:t13039_refactoring.

[Jun Omae]

Replying to Ryan J Ollos:

I did some refactoring in rjollos.git:t13039_refactoring.

Looks good to me.

[Ryan J Ollos]

I did some refactoring in r16637, but didn't run all the tests. I didn't consider that modifying the Request class would persist outside the scope of the module. Fixed in r16638.

[Ryan J Ollos]

After this ticket is concluded I'll propose some related changes in #13042.

[Ryan J Ollos]

Committed to trunk in r16656.