[IronPython] Weird Anomoly with SetStandardOutput

[Michael Foord]

Hello all,

If I create a subclass of 'Stream' from IronPython - and set it onto a 
PythonEngine using 'SetStandardOutput', then it fails with the following 
message:

Traceback (most recent call last):
  File C:\Python Projects\modules in 
progress\ironpython\embeddingDivert.py, lin
e 32, in Initialize
  File , line 0, in SetStandardOutput##94
TypeError: issubclass: arg 1 must be a class

If I define an empty class, and set this then I get the expected error 
'AttributeError: 'Diverter' object has no attribute 'get_CanSeek'.

What is weird, is if I add the required methods and properties one at a 
time to the class (which the instance then acquires) - eventually it 
works !!

Unfortunately this problem is going to block us very rapidly at 
resolver. We can probably get round it by creating the stream subclass 
in C# - but what is the problem with doing it from IronPython ?

Below is a full interactive interpreter session showing what happens as 
I add methods to a class dynamically :

 >>> from IronPython.Hosting import PythonEngine
 >>> from System.IO import Stream
 >>> py = PythonEngine()
 >>> class Diverter(Stream): pass
...
 >>> output = Diverter()
 >>> py.SetStandardOutput(output)
Traceback (most recent call last):
AttributeError: 'Diverter' object has no attribute 'get_CanRead'
 >>>
 >>> Diverter.CanRead = lambda self: False
 >>> py.SetStandardOutput(output)
Traceback (most recent call last):
AttributeError: 'Diverter' object has no attribute 'get_CanSeek'
 >>> Diverter.CanSeek = lambda self: False
 >>> py.SetStandardOutput(output)
Traceback (most recent call last):
AttributeError: 'Diverter' object has no attribute 'get_Position'
 >>> Diverter.Position = property(lambda self: 0)
 >>> py.SetStandardOutput(output)
Traceback (most recent call last):
AttributeError: 'Diverter' object has no attribute 'get_CanWrite'
 >>> Diverter.CanWrite = lambda self: True
 >>> py.SetStandardOutput(output)
 >>> py.Execute('print 3')
Traceback (most recent call last):
AttributeError: 'Diverter' object has no attribute 'Write'
 >>> def Write(self, chars, offset, count):
...   sys.stdout.write(repr(chars))   # silly buggy implementation
...
 >>> Diverter.Write = Write
 >>> import sys
 >>> py.Execute('print 3')
System.Byte[](51, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0
, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0
, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
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0, 0, 0
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0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
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0, 0, 0
, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
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0, 0, 0
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0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
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0, 0, 0
, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
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0, 0, 0
, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
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0, 0, 0
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0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
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0, 0, 0
, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0
, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0,
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0
, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)Traceback (most recent 
call las
t):
  File , line 0, in <stdin>##126
  File , line 0, in Execute##116
  File , line 0, in <string>##127
  File , line 0, in Write##121
  File mscorlib, line unknown, in Flush
  File mscorlib, line unknown, in Flush
AttributeError: 'Diverter' object has no attribute 'Flush'
 >>>