[Patches] [ python-Patches-769142 ] CallTip trimming may loop forever.

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Patches item #769142, was opened at 2003-07-10 14:13
Message generated for change (Settings changed) made by scott_daniels
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https://sourceforge.net/tracker/?func=detail&atid=305470&aid=769142&group_id=5470

Category: IDLE
Group: Python 2.3
Status: Open
Resolution: None
>Priority: 7
Submitted By: Scott David Daniels (scott_daniels)
Assigned to: Nobody/Anonymous (nobody)
Summary: CallTip trimming may loop forever.

Initial Comment:
(also applies to 2.2.x)    
  
While trying to understand someone else's half-developed code, I found   
an interesting problem in Idle.  This bug is far nastier in 2.3 (which   
I was using at the time).  
  
testcase.py:  
  
    def function(arg):  
        '''  
        '''  
        return 1  
  
  
In Idle if you type  
>>> import testcase  
>>> testcase.function(  
  
The code will loop trying to place a calltip in 2.3 (in 2.2.0, it  
raises an exception).  
  
After investigation, I found the following code:  
  
python/dist/src/Lib/idlelib/CallTips.py:  
...  while doc[:1] in " \t\n":  
        doc = doc[1:]  
     pos = doc.find("\n")  
...  
  
With the new string semantics for 'in', this loop will be  
checking ('' in ' \t\n') (a bad state of affairs).  
  
  
The following patch should fix it:  
  
*** CallTips.py        Thu Jun 26 01:16:56 2003  
--- CallTips.py_old    Tue Dec 31 07:59:14 2002  
***************  
*** 164,175 ****  
          # See if we can use the docstring  
          doc = getattr(ob, "__doc__", "")  
          if doc:  
!             doc = doc.lstrip()  
              pos = doc.find("\n")  
              if pos < 0 or pos > 70:  
                  pos = 70  
!             if argText and doc:  
                  argText += "\n"  
!             argText = (argText + doc[:pos]).rstrip()  
      return argText  
  
--- 164,176 ----  
          # See if we can use the docstring  
          doc = getattr(ob, "__doc__", "")  
          if doc:  
!             while doc[:1] in " \t\n":  
!                 doc = doc[1:]  
              pos = doc.find("\n")  
              if pos < 0 or pos > 70:  
                  pos = 70  
!             if argText:  
                  argText += "\n"  
!             argText += doc[:pos]  
      return argText  
  
  
  
Unit tests are tricky (since the 2.3 problem is an infinite loop):  
Attached is a test that won't get stuck in a loop. 
  
  
-Scott David Daniels  
Scott.Daniels@Acm.Org  
  

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