This patch causes multiple with statements with multiple with items to be represented in the AST instead of flattened as currently happens.

Here is an improved patch. Sans comments, I will apply in a few days.

Just to articulate the rationale, I'm guessing the reasoning behind this is to make it feasible for source->AST->source translators to retain the original grouping?

Visual scan of the patch in Reitveld looks fine to me.

2011/5/24 Nick Coghlan <report@bugs.python.org>:
>
> Nick Coghlan <ncoghlan@gmail.com> added the comment:
>
> Just to articulate the rationale, I'm guessing the reasoning behind this is to make it feasible for source->AST->source translators to retain the original grouping?

Correct. It also allows my Python static analysis tool to detect when
someone could be using the double with shorthand instead of
nested-withs.

New changeset 9b11cc4e2918 by Benjamin Peterson in branch 'default':
reflect with statements with multiple items in the AST (closes #12106)
http://hg.python.org/cpython/rev/9b11cc4e2918

Does this change have a visible effect? If so, can it have some unit test? Otherwise pypy and other alternative implementations are likely to miss this change.

The AST version changed, and, more importantly, if other implementations pick up our AST changes without updating their compilers accordingly, their symbol table analysis and code compilation processes will break.

So yes, the test suite does already cover this change.

For the record:
3.2: ast.__version__ == 82163
3.3: ast.__version__ == 0daa6ba25d9b

(The latter is only the 3.3 AST version for the moment - there are additional AST cleanups planned for 3.3 now that the other projects gave their blessing to do so on python-dev)

Thanks for this answer.

One other thing I should mention is that in a later checkin, Benjamin did add a couple of explicit with statement examples to test_ast. These will fail if other implementations don't update the front end of their compilation processes correctly, so that should eliminate cases of counteracting bugs in the front end and back end.

That would be c4ddb460f4f2.