[Bugs] #1775 UNSP: view source functionality should be more robust against buggy activities

[Sugar Labs Bugs]

#1775: view source functionality should be more robust against buggy activities
------------------------------------------+---------------------------------
    Reporter:  rgs                        |          Owner:  tomeu                      
        Type:  defect                     |         Status:  new                        
    Priority:  Unspecified by Maintainer  |      Milestone:  Unspecified by Release Team
   Component:  sugar                      |        Version:  Git as of bugdate          
    Severity:  Unspecified                |       Keywords:  robust file existence check
Distribution:  Unspecified                |   Status_field:  Unconfirmed                
------------------------------------------+---------------------------------
 Scenario:

 We added view-source support to TurtleArt (see attached code snippet). I
 manage to hit a code path (a race condition somewhere or problem accessing
 the temp file) in which I got the following exception (in
 ~/.sugar/default/logs/shell.log):


 {{{
 File "/usr/lib/python2.6/dist-packages/jarabe/view/viewsource.py",  line
 291, in __init__
  activity_button.props.group = document_button
  UnboundLocalError: local variable 'document_button' referenced before
 assignment
 }}}

 Checking the constructor of the Toolbar class in jarabe/view/viewsource.py
 it seems like the following test:

 {{{
  if document_path is not None:
 }}}

 forgets to check file existence as the previous conditional does:


 {{{
  if document_path is not None and os.path.exists(document_path)
 }}}



 The attached patch proposes a fix by starting document_button to None
 which seems cheaper then testing for the existence of a file twice.

-- 
Ticket URL: <http://bugs.sugarlabs.org/ticket/1775>
Sugar Labs <http://sugarlabs.org/>
Sugar Labs bug tracking system