IDLE: Calltip fails if __getattr__ raises exception #60834

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1. serwy commented on Dec 7, 2012

   

   serwymannequin

   on Dec 7, 2012

   MannequinAuthor

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   The calltip fails if __getattr__ raises an exception. Take as an example:

   Python 3.4.0a0 (default:0238cc842805+, Dec  6 2012, 19:17:04) 
   [GCC 4.7.2] on linux
   Type "copyright", "credits" or "license()" for more information.
   >>> class Test:
   	def __getattr__(self, name):
   		raise Exception()

   >> a = Test()
   >> a(

   This traceback is sent to stderr:

   Exception in Tkinter callback
   Traceback (most recent call last):
     File "/home/serwy/Code/python/cpython/Lib/tkinter/__init__.py", line 1442, in __call__
       return self.func(*args)
     File "/home/serwy/Code/python/cpython/Lib/idlelib/MultiCall.py", line 166, in handler
       r = l[i](event)
     File "/home/serwy/Code/python/cpython/Lib/idlelib/CallTips.py", line 56, in try_open_calltip_event
       self.open_calltip(False)
     File "/home/serwy/Code/python/cpython/Lib/idlelib/CallTips.py", line 75, in open_calltip
       argspec = self.fetch_tip(expression)
     File "/home/serwy/Code/python/cpython/Lib/idlelib/CallTips.py", line 101, in fetch_tip
       (expression,), {})
     File "/home/serwy/Code/python/cpython/Lib/idlelib/rpc.py", line 216, in remotecall
       return self.asyncreturn(seq)
     File "/home/serwy/Code/python/cpython/Lib/idlelib/rpc.py", line 247, in asyncreturn
       return self.decoderesponse(response)
     File "/home/serwy/Code/python/cpython/Lib/idlelib/rpc.py", line 267, in decoderesponse
       raise what
   Exception

   The attached patch fixes the issue.
2. serwy

   added

   topic-IDLE

   easy

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Dec 7, 2012
3. serhiy-storchaka commented on Dec 7, 2012

   

   serhiy-storchaka

   on Dec 7, 2012

   Member

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   1. rpcclt.remotecall also can raise an exception.

   2. I think fetch_tip() should return '' in case of exception as for non-existent arguments or for non-callables. You can add tests for this cases too.

   3. "break" is a reserved word. It's not a good name for an attribute.

   4. It will be better test for exception an instance of the special class and not break TC.

   class Broken:
       def __getattr__(self, name):
           raise Exception('Broken __getattr__')
   
   brocken = Broken()
   test('brocken', '')
4. serhiy-storchaka

   self-assigned this

   on Dec 29, 2012
5. terryjreedy commented on Jan 10, 2014

   

   terryjreedy

   on Jan 10, 2014

   Member

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   Get_entity already has try-except to block exceptions propagating from eval failure, so wrapping it is redundant. We only need worry about get_argspec.

   I presume the failure is in get_argspec in the remote process:
   if hasattr(ob, '__call__'):
   This can be replaced by callable(ob) as it converts exceptions to False. The appropriate return for non-callables is the current default, '', which results in no tip.

   There are, however, other attribute accesses that could fail. I am reluctant to wrap get_argspec in its entirety, as that would mask bugs in Idle code as well as in user snippets. So I think each access should be protected. Since users will expect a tip for something that is a callable, I think a message might be appropriate. I checked that getattr(ob, name, default) does not convert exception to default.

   Their are rpc calls in several places in Idle code. Unless failure can be triggered here in particular by user error, I do not think we should add specific protection here.
6. python-dev commented on Jan 21, 2014

   

   python-devmannequin

   on Jan 21, 2014

   Mannequin

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   New changeset d55d1cbf5f9a by Terry Jan Reedy in branch '2.7':
   Issue bpo-16630: Make Idle calltips work even when __getattr__ raises.
   http://hg.python.org/cpython/rev/d55d1cbf5f9a

   New changeset 2fe0b2dcc98c by Terry Jan Reedy in branch '3.3':
   Issue bpo-16630: Make Idle calltips work even when __getattr__ raises.
   http://hg.python.org/cpython/rev/2fe0b2dcc98c
7. terryjreedy commented on Jan 21, 2014

   

   terryjreedy

   on Jan 21, 2014

   Member

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   I added test_attribute_exception with two subtests for each of two nasty classes. The resulting failures were fixed in CallTips.py by replacing all ob.__call__ references with one reference inside try_except that saved the method for possible later use.
8. terryjreedy

   closed this as completedon Jan 21, 2014
9. terryjreedy

   assigned

   terryjreedy

   and unassigned

   serhiy-storchaka

   on Jan 21, 2014
10. ezio-melotti

    transferred this issue fromon Apr 10, 2022