bare excepts

[Robert Collins]

On Tue, 2006-01-03 at 11:39 -0500, Aaron Bentley wrote:
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> Robert Collins wrote:
> > On Tue, 2006-01-03 at 01:28 -0500, Aaron Bentley wrote:
> > 
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> >>Robert Collins wrote:
> >>| I'd be happy to extend my code-practices tests to check for:
> >>| except:
> >>| except Exception[ ,].*
> >>| What do you think? (They are persistent little buggers, keep coming
> >>| back.)
> >>
> >>I think we'd need a way to flag some of the second type as legit.  And
> >>there's a risk of improper flagging, then.  But on the whole, sure.
> > 
> > 
> > I'll put in a counter - which we can change as needed - to accomodate
> > the aggregate legit ones. That said, I *still* have never seen one.
> 
> What about the exception logging?
> 
>     except Exception, e:
>         # used to handle AssertionError and KeyboardInterrupt
>         # specially here, but hopefully they're handled ok by the logger now
>         import errno
>         if (isinstance(e, IOError)
>             and hasattr(e, 'errno')
>             and e.errno == errno.EPIPE):
>             bzrlib.trace.note('broken pipe')
>             return 3
>         else:
>             bzrlib.trace.log_exception()
>             if os.environ.get('BZR_PDB'):
>                 print '**** entering debugger'
>                 import pdb
>                 pdb.post_mortem(sys.exc_traceback)
>             return 3

AssertionError and KeyboardInterrupt still should not be caught
unless we *want* them to drop into the debugger here.
if we do - then the comment is wrong, otherwise the following will be
buggy. And yes, I'll admit thata this is a valid use of bare excepts -
but only because its 'drop into the debugger' - its not used for flow
control or error handling. I'd write it as follows:

def do_debug():
    """Print the exception we have encountered.

    If we have post mortem mode enabled, drop into the debugger.
    """
    bzrlib.trace.log_exception()
    if os.environ.get('BZR_PDB'):
        print '**** entering debugger'
        import pdb
        pdb.post_mortem(sys.exc_traceback)
    return 3

except IOError, e:
    # all IOErrors have errno
    if e.errno == errno.EPIPE:
        bzrlib.trace.note('broken pipe')
        return 3
    return do_debug()
except:
    # this catches string exceptions which
    # except Exception, e: does not.
    return do_debug()
    

Rob

-- 
GPG key available at: <http://www.robertcollins.net/keys.txt>.
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