Message3439

Author akruis
Recipients akruis, leosoto
Date 2008-08-19.11:58:36
SpamBayes Score 1.30507e-13
Marked as misclassified No
Message-id <1219147118.67.0.799494758901.issue1095@psf.upfronthosting.co.za>
In-reply-to
Content
The attached patch fixes this issue.

Some details: In my test case an old style class implements
__getattr__(self, name). An access of an otherwise undefined attribute
yields the following JAVA stack trace (just the interesting part):

        at org.python.core.PyFunction.__call__(PyFunction.java:312)
        at org.python.core.PyInstance.ifindfunction(PyInstance.java:238)
        at org.python.core.PyInstance.__findattr__(PyInstance.java:217)
        at org.python.core.PyInstance.__findattr_ex__(PyInstance.java:204)
        at org.python.core.PyObject.__getattr__(PyObject.java:820)
        at org.python.pycode._pyx0.f$0(testAttributeError.py)

Inspection of this code path shows:
  - the call of a __findattr__-method, which indicates a problem,
because the __findattr__ methods never throw AttributeError
  - org.python.core.PyInstance#ifindfunction(String) catches PyException
and returns null in case of an AttributeError. (In PyObject#__getattr__
 this null return value yields an AttributeError.)
 
I looked at the clients of PyInstance#ifindfunction(String). The method
is only used within PyInstance. In every case, we see the same pattern

  value=this.ifindfunction(name);
  ...
  if (value==null)
     noAttributeError(name);

Therefore it does not harm, to remove the try-catch clause from
ifindfunction. Of course we have to make sure, that the __findattr__
methods still return null instead of an AttributeError. Therefor I added
a new method PyInstance#__findattr_ex__(String name, boolean stopAtJava)
and changed PyInstance#__findattr__(String name, boolean stopAtJava) to
call the new method.

With the patch applied, the relevant parts of a stack trace look like this:

        at org.python.core.PyFunction.__call__(PyFunction.java:312)
        at org.python.core.PyInstance.ifindfunction(PyInstance.java:246)
        at org.python.core.PyInstance.__findattr_ex__(PyInstance.java:226)
        at org.python.core.PyInstance.__findattr_ex__(PyInstance.java:204)
        at org.python.core.PyObject.__getattr__(PyObject.java:820)
        at org.python.pycode._pyx0.f$0(testAttributeError.py)

No more __findattr__ methods. Looks good for me.
History
Date User Action Args
2008-08-19 11:58:38akruissetmessageid: <1219147118.67.0.799494758901.issue1095@psf.upfronthosting.co.za>
2008-08-19 11:58:38akruissetrecipients: + akruis, leosoto
2008-08-19 11:58:38akruislinkissue1095 messages
2008-08-19 11:58:37akruiscreate