Re: [KVM-AUTOTEST PATCH v2 3/6] [RFC] Introduce exception context strings

[Michael Goldish <mgoldish@redhat.com>]

On 01/05/2011 06:21 PM, Eduardo Habkost wrote:
> On Wed, Jan 05, 2011 at 06:12:05PM +0200, Avi Kivity wrote:
>> It would be nice to make the error context a stack, and to use the
>> with statement to manage the stack:
>>
>>
>>    with error.context("main test"):
>>        foo()
>>        with error.context("before reboot"):
>>            bar()
>>
>> If foo() throws an exception, the context would be "main test",
>> while if bar() throws an exception, the context would be "before
>> reboot" in "main test".
> 
> Autotest targets Python 2.4, and Python 2.4 doesn't have the 'with'
> statement.
> 
> The error context is already a stack, but without the 'with' statement
> you would have to use try/finally explicitly:
> 
>   _new_context('foo')
>   try:
>     # [...]
>   finally:
>     _pop_context()
> 
> By the way, I think we could make _new_context() and _pop_context() part
> of the public interface (i.e. remove the "_" from their names).  I see
> @context_aware as just a helper for a stack interface that could be used
> directly if needed.

To actually use the context you also have to insert it into an
exception, i.e.

_new_context('foo')
try:
    try:
        ...
    except Exception, e:
        e._context = get_context()
finally:
    _pop_context()

and I thought it would be more comfortable to just define a
@context_aware function and call it.