[jira] Closed: (MODPYTHON-91) Improve error message when "quit" run in pdb debugger.

["Graham Dumpleton (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MODPYTHON-91?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Graham Dumpleton closed MODPYTHON-91.
-------------------------------------


> Improve error message when "quit" run in pdb debugger.
> ------------------------------------------------------
>
>                 Key: MODPYTHON-91
>                 URL: https://issues.apache.org/jira/browse/MODPYTHON-91
>             Project: mod_python
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 3.3
>            Reporter: Graham Dumpleton
>         Assigned To: Graham Dumpleton
>            Priority: Minor
>             Fix For: 3.3
>
>
> If one has enabled PythonEnablePdb and correctly running "httpd" with -DONE_PROCESS option, in the debugger, if you run the "quit" command in the debugger, you get back the result 500 error message reads as:
>   Mod_python error: "PythonHandler mptest"
>   Traceback (most recent call last):
>     File "/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/site-packages/mod_python/apache.py", line 313, in HandlerDispatch
>       assert (type(result) == type(int())), \
>   AssertionError: Handler 'mptest' returned invalid return code.
> It might be nice to have an error response which actually indicates in some way that the debugger was explicitly quit for the request that was being debugged.
> The reason that the error above occurs now is that the debugger support uses the call:
>   result = pdb.runcall(object, conn)
> This ultimately executes bdb.Bdb.runcall();
>     def runcall(self, func, *args):
>         self.reset()
>         sys.settrace(self.trace_dispatch)
>         res = None
>         try:
>             try:
>                 res = func(*args)
>             except BdbQuit:
>                 pass
>         finally:
>             self.quitting = 1
>             sys.settrace(None)
>         return res
> As can be seen, the exception BdbQuit indicating that the "quit" command had been run is caught and ignored, with the result that None is then returned as if from the handler itself. This causes the upstream exception to be raised that the result is not an integer.
> One possibility is run replace pdb.runcall() invocation with:
>                         #result = pdb.runcall(object, req)
>                         debugger = pdb.Pdb()
>                         debugger.reset()
>                         sys.settrace(debugger.trace_dispatch)
>                         try:
>                             return object(req)
>                         finally:
>                             debugger.quitting = 1
>                             sys.settrace(None)
> If this is done, the BdbQuit exception ignored and is propogated up. The error message then at least can be linked better as being related to the debugger.
>   Mod_python error: "PythonHandler mptest"
>   Traceback (most recent call last):
>     File "/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/site-packages/mod_python/apache.py", line 303, in HandlerDispatch
>       return object(req)
>     File "/Users/grahamd/Sites/importer/mptest.py", line 5, in handler
>       req.content_type = 'text/plain'
>     File "/Users/grahamd/Sites/importer/mptest.py", line 5, in handler
>       req.content_type = 'text/plain'
>    File "/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/bdb.py", line 48, in trace_dispatch
>       return self.dispatch_line(frame)
>     File "/System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/bdb.py", line 61, in dispatch_line
>       if self.quitting: raise BdbQuit
>   BdbQuit
> Alternatively a special purpose error message could be generated to indicate that the debugging of the handler for that request was explicitly quit.

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