I am a little confused how you get from "there are extra frames in the traceback" to "modify exec() to run code in another frame".

Also, with PEP 558 (Defined semantics for locals(), by Nick Coghlan) we might be able to just pass the frame's globals and locals to exec() or eval() without further changes (or perhaps just with changes to allow passing a proxy instead of a true dict).

On Mon, Feb 17, 2020 at 11:36 PM Serhiy Storchaka <storchaka@gmail.com> wrote:
The idea is inspired by the following StackOverflow question:
https://stackoverflow.com/questions/40945752/inspect-who-imported-me and
the corresponding BPO issue: https://bugs.python.org/issue39643.

In the older Python versions the f_back attribute of the frame in which
the module code is executed pointed to the frame which executes the
import statement or calls __import__() or import_module(). But after
rewriting the import machinery in Python, there are other frames between
the caller frame and the calling frame. This caused problems with
tracebacks which was worked around by removing intermediate frames
related to the import machinery when the exception floats to the caller.
But there is still unresolved problem with warnings, and all frames of
the import machinery are visible from the imported code.

I propose to add possibility to execute the code in the context of
different frame. Either add a frame argument in exec() and eval(), which
will allow to pass an arbitrary frame. Or add a stacklevel argument in
exec() and eval() (similar to warnings.warn()), which will limit
possible frames to the parent frames of the current frame. I do not know
what is more feasible.

This will automatically fix problems with warnings. This will allow to
get rid the workaround for exceptions, and may make the code simpler.
This will allow the imported code to do miscellaneous magic things with
the code which performs the import.

What do you think about this?
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