[Ironpython-users] WDB web debugger for IronPython

Kerray kerray.cz at gmail.com
Mon Nov 24 13:53:48 CET 2014

Hi everyone,
We're using IronPython to script the insides of SharePoint (ASP.NET
<http://asp.net/> on IIS). For quite some time, I've been looking for a
comfortable way to debug these scripts without having to install Visual

I've considered using standard PDB, with console redirected over the net by
some sort of messaging. This was the least preferable option, as the user
comfort is quite low and we'd have to take care of the messaging layer.

I also considered using IPython to do this, but despite using
https://github.com/paweljasinski/ repositories, I haven't been anywhere
close to success.

However, recently I've re-visited https://github.com/Kozea/wdb and was
surprised how far it has come since I've seen it for the first time. It
looked exactly like the debugger I was looking for. I tried playing with
it, added small IPy compatibility changes here and there, and the results
are promising.

I've been attacking this on two fronts:

1) I've tried running the server side in IronPython, but it uses Tornado,
and while I can get it to run (using
https://github.com/paweljasinski/tornado), on client connect the server
 fails with
Exception in I/O handler for fd 1492
    Traceback (most recent call last):
      File "c:\Program Files (x86)\IronPython
2.7\lib\site-packages\tornado-3.1.1-py2.7.egg\tornado\iostream.py", line
694, in read_from_fd
        chunk = self.socket.recv(self.read_chunk_size)
    error: [Errno 10022] A request to send or receive data was disallowed
because the socket is not connected and (when sending on a datagram socket
using a sendto call) no address was supplied

While the client reports:
site-packages\wdb\_compat.py", line 135, in recv_bytes
    size, = struct.unpack("!i", self._handle.recv(4))
struct.error: unpack requires a string argument of length 4

But seeing my added debug output, the server and the client have
successfully communicated over the socket at least once, succesfully
sending and receiving a guid, and then crash on the message "ServerBreaks"
which should get server breakpoints.

Could this be an error with how sockets are handled in IPy/Windows? I've no

2) I've also tried running the server side in Python, and the client in
IronPython (as I wouldn't mind doing it like this), but this also fails with
File "c:\Program Files (x86)\IronPython
2.7\lib\site-packages\wdb-2.0.7-py2.7.egg\wdb\__init__.py", line 575, in
TypeError: Unable to cast object of type
'System.Linq.Expressions.FieldExpression' to type

And I've been unable to get any further from here - the line 575 in
question contains
startlnos = dis.findlinestarts(code)
and even when I take the dis.findlinestarts function, put it into the file
in question, and enhance it with debug output, it seem the call doesn't
come through to the inside of the function as none of the debug output

Both points seem to me more like IronPython issues than an issues with WDB
directly, which is why I'm trying to ask here.

This is far too deep in the insides for my shallow "expertise", but I'd be
grateful for any pointers or ideas as to what to try next.

Thanks - and have a nice day

Jaromír Matýšek
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