Re: [Fab-user] exceptions, and finally()

[Jeff Forcier]

Hi Rob,

On Fri, Jun 3, 2011 at 5:14 PM, Robert Terhaar
<address@hidden> wrote:
> Hi All,
>
> I know that Fabric does not currently use Python's built-in exceptions (as
> noted in bug http://code.fabfile.org/issues/show/277 ) However-
>
> It is possible to still wrap tasks inside a try(): for purposes of using
> finally(): as a way to implement pseudo roll-backs?

Fabric uses sys.exit() to abort, which raises SystemExit, so it does
play nicely with try/except/finally even though it's not specific like
it should be (re: the ticket). So you can use any combo of except and
finally as you would normally, or do both, eg:

    >>> from fabric.api import abort
    >>> try:
    ...     abort("Ohnoes!") # or any Fab code that might call abort()
or sys.exit() at some point, namely most of it
    ... except SystemExit:
    ...     print "Would exit here, but we're not gonna"
    ... finally:
    ...     print "One more thing"
    ...
    ...

    Fatal error: Ohnoes!

    Aborting.
    Would exit here, but we're not gonna
    One more thing
    >>> # haven't exited!

Again, you could just use try: / :finally and not even bother with the
SystemExit test, which would have the minor benefit of working in the
future when we do move to real exception raising.

HTH,
Jeff

-- 
Jeff Forcier
Unix sysadmin; Python/Ruby engineer
http://bitprophet.org