RuntimeError: headers have already been sent

[Velu Narasimman]

Hi team,

    I am facing this "headers have already been sent" error in an AJAX call. I am not able to fix it. I need your hellp. Would be better if someone could explain this issue.

2020-03-04 11:00:45,582 Trac[main] ERROR: [172.24.188.116] Internal Server Error: <RequestWithSession "POST '/admin/pros users/users'">, referrer 'https://prism30.aspiresys.com/Merlin/admin/pros%20users/users'
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/Trac-1.0.15-py2.7.egg/trac/web/main.py", line 631, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/local/lib/python2.7/dist-packages/Trac-1.0.15-py2.7.egg/trac/web/main.py", line 325, in dispatch
    req.send(output, content_type or 'text/html')
  File "/usr/local/lib/python2.7/dist-packages/Trac-1.0.15-py2.7.egg/trac/web/api.py", line 556, in send
    self.end_headers()
  File "/usr/local/lib/python2.7/dist-packages/Trac-1.0.15-py2.7.egg/trac/web/api.py", line 476, in end_headers
    self._write = self._start_response(self._status, self._outheaders)
RuntimeError: headers have already been sent

Above chunk is the error. And below is how I write my json response to the AJAX call.

    def respond(self, req, data, code=200):
        """Respond to the JSON request by sending the JSON-encoded data back."""
        json_data = json.dumps(data)
        req.send_response(code)
        req.send_header('Content-Type', 'application/json')
        req.send_header('Content-Length', len(json_data))
        req.write(json_data)
        raise RequestDone

Not sure if I am missing any code here in this respond method. Welcome your suggestions to fix this error.

[Jun Omae]

That is due to Request.end_headers() called twice. Please report it to
the plugin maintainers.

--
Jun Omae <jun...@gmail.com> (大前 潤)

[Velu Narasimman]

This error is happening in the core Trac package. Whom should I report to? Also I am using similar code in few other area. There it works well.

[Jun Omae]

Please share entire of the plugin code. I believe the plugin has the problem(s).

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[Velu Narasimman]

Sorry, do you mean the Trac code? I am using trac 1.0.15 version and you can find the same here. Now it is archived.

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[Jun Omae]

No. Please share your installed plugin, not Trac. The installed plugin has something wrong and the wrong leads the error.

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[Jun Omae]

In addition, post System Information, Installed Plugins and configuration from about page of your Trac.

On Thu, Mar 5, 2020 at 0:03 Jun Omae <jun...@gmail.com> wrote:

No. Please share your installed plugin, not Trac. The installed plugin has something wrong and the wrong leads the error.

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