Issue1462188

Under jython 2.2 (latest and previous build) attempting to access 
specifically the __doc__ attribute of objects of built in classes fails.
The example uses "dict" but the bug is not specific to this.  

Other classes may also be affected. The behavior was first seen 
introspecting the on an object of the PatternObject class in the re 
module.

E.g.

>>> d = dict()
>>> dir(d)
['__class__', '__cmp__', '__contains__', '__delattr__', '__delitem__', 
'__doc__', '__eq__', '__getattribute__', '__getitem__', '__hash__', '__init__', 
'__iter__', '__len__', '__ne__', '__new__', '__repr__', '__setattr__', 
'__setitem__', '__str__', '__unicode__', 'clear', 'copy', 'fromkeys', 'get', 
'has_key', 'items', 'iteritems', 'iterkeys', 'itervalues', 'keys', 'pop', 
'popitem', 'setdefault', 'update', 'values']
>>> d.__class__
<type 'dict'>
>>> d.__doc__
Traceback (innermost last):
  File "<console>", line 1, in ?
java.lang.NullPointerException
	at org.python.core.PyObject.getDoc(Unknown Source)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at 
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorIm
pl.java:39)
	at 
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAc
cessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:324)
	at org.python.core.PyGetSetDescr.__get__(Unknown Source)
	at org.python.core.PyObject.object___findattr__(Unknown Source)
	at org.python.core.PyObject.__findattr__(Unknown Source)
	at org.python.core.PyObject.__getattr__(Unknown Source)
	at org.python.pycode._pyx11.f$0(<console>:1)
	at org.python.pycode._pyx11.call_function(<console>)
	at org.python.core.PyTableCode.call(Unknown Source)
	at org.python.core.PyCode.call(Unknown Source)
	at org.python.core.Py.runCode(Unknown Source)
	at org.python.core.Py.exec(Unknown Source)
	at org.python.util.PythonInterpreter.exec(Unknown Source)
	at org.python.util.InteractiveInterpreter.runcode(Unknown Source)
	at org.python.util.InteractiveInterpreter.runsource(Unknown 
Source)
	at org.python.util.InteractiveInterpreter.runsource(Unknown 
Source)
	at org.python.util.InteractiveConsole.push(Unknown Source)
	at org.python.util.InteractiveConsole.interact(Unknown Source)
	at org.python.util.jython.main(Unknown Source)

java.lang.NullPointerException: java.lang.NullPointerException

Logged In: NO 

It can be fixed the way that the NPE doesn't occur anymore.
But, if there is no documentation string for dict (and BTW,
for other built-in types as well), an AttributeError will be
thrown. So, what should we do ? Hm, when we look at CPython,
we can see that, here too, dict for example has a very poor
documentation string. The same applies to list. Maybe we
should simply return an empty string. 

What do others think ? 

Logged In: YES 
user_id=369541

> cvs diff PyObject.java
Index: PyObject.java
===================================================================
RCS file: /cvsroot/jython/jython/org/python/core/PyObject.java,v
retrieving revision 2.43
diff -r2.43 PyObject.java
388c388,394
<         PyObject doc = fastGetDict().__finditem__("__doc__");
---
>
>         PyObject dict = fastGetDict();
>         if(dict == null) {
>             return Py.None;
>         }
>
>         PyObject doc = dict.__finditem__("__doc__");

Logged In: YES 
user_id=18288


Thanks gene9, that null-guard in PyObject:getDoc() fixes the
exception for me. Probably at some point we can also add the
docs to dict & friends, copying cpython.

- kz

Logged In: YES 
user_id=1174327

Looks like the nullguard from gene9 has already been applied
so I'm closing this.