Delegating generators do not show always up in stack traces, such as inspect.stack().
The show up during the first delegation, but not thereafter.

I have attached a patch. It alters the way the YIELD_FROM bytecode works; it loops back on itself. This ensures the delegator's frame is always in the trace.

Unfortunately I started working on it before Benjamin fixed issue 14220
(rev 3357eac1ba62). By the nature of it, this patch necessarily fixes most of issue  14220, so I have just included the tests for issue 14220
in this patch as well.
So in order to apply this, 3357eac1ba62 will have to be backed out.
Sorry for the overlap.

Mark's patch looks good on a quick read through (although I still need to double check where f_lasti gets incremented to be happy the new comment about YIELD_FROM is accurate). 

If someone gets to this soon, great, otherwise I'll deal with it after I finish moving house.

I would appreciate the patch could be regenerated against the latest default.

Updated Patch

Mercurial complains when trying to apply the patch:

applying yieldfrom.patch
patching file Lib/test/test_pep380.py
Hunk #2 succeeded at 921 with fuzz 2 (offset 72 lines).
abort: bad hunk #1 @@ -20,7 +20,6 @@
 (7 7 7 6)

Could you try this new patch (with white space changes included)?

New changeset 72556ff86828 by Benjamin Peterson in branch 'default':
perform yield from delegation by repeating YIELD_FROM opcode (closes #14230)
http://hg.python.org/cpython/rev/72556ff86828

This changeset has broken something. All I get is a confusing backtrace ending with:

  File "/home/matt/src/python-torrent/torrent/bencode.py", line 15, in encode
    yield from encode(k)
AttributeError: 'list_iterator' object has no attribute 'send'

Backing out the changeset, and there is no problem. Let me know if there's some way to provide more information.

2012/3/16 Matt Joiner <report@bugs.python.org>:
>
> Matt Joiner <anacrolix@gmail.com> added the comment:
>
> This changeset has broken something. All I get is a confusing backtrace ending with:
>
>  File "/home/matt/src/python-torrent/torrent/bencode.py", line 15, in encode
>    yield from encode(k)
> AttributeError: 'list_iterator' object has no attribute 'send'
>
> Backing out the changeset, and there is no problem. Let me know if there's some way to provide more information.

Try removing all the pycs.

Nevermind, I think I see the problem.

2012/3/16 Benjamin Peterson <report@bugs.python.org>:
>
> Benjamin Peterson <benjamin@python.org> added the comment:
>
> 2012/3/16 Matt Joiner <report@bugs.python.org>:
>>
>> Matt Joiner <anacrolix@gmail.com> added the comment:
>>
>> This changeset has broken something. All I get is a confusing backtrace ending with:
>>
>>  File "/home/matt/src/python-torrent/torrent/bencode.py", line 15, in encode
>>    yield from encode(k)
>> AttributeError: 'list_iterator' object has no attribute 'send'
>>
>> Backing out the changeset, and there is no problem. Let me know if there's some way to provide more information.
>
> Try removing all the pycs.
>
> ----------
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <http://bugs.python.org/issue14230>
> _______________________________________

Can you possibly create a small example that fails?

The magic number has not been updated

Patch attached.

New changeset c0a6569fdad6 by Benjamin Peterson in branch 'default':
in 72556ff86828, I should have updated the magic as well as the comment (#14230)
http://hg.python.org/cpython/rev/c0a6569fdad6