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Is it possible to get the current function in a trace function?
I'm trying to subclass pdb to have a debugger that, in case of a call to a decorated function, can "step in" the decorated function directly and skip the decorator content altogether. A well-behaved decorator using @functools.wraps sets __wrapped__ attribute on the wrapper to point to the decorated function and inspect.unwrap can follow a chain of such decorators.
So, I need access to the function object, but the trace function gives me the frame only and I don't know how to get the function object out of it.
1 answer
The following users marked this post as Works for me:
| User | Comment | Date |
|---|---|---|
| luser | (no comment) | May 7, 2023 at 13:10 |
CPython only very recently started keeping a reference on frames to function objects internally, and that reference isn't exposed from inside Python.
There's an old PEP that would have defined a __function__ local, which, combined with the f_locals field on frame objects, probably would have done what you needed. Unfortunately, the PEP was rejected, and I don't see any current activity in the direction of exposing a frame's function object via any other means.
For limited cases, if you make various assumptions about what variables are named or what kind of functions get decorated, you can possibly bodge in something that will work some of the time by inspecting a parent frame's f_locals and f_globals and looking for a function object that matches what the current frame is doing. But a technique suitable for a general-purpose debugger is probably impossible.
You probably already know, but the Pdb class accepts a skip argument which allows the debugger to skip code in modules that match wildcards. Depending on which decorators you need to skip and how you structure your code, using this feature might be better for you than attempting to subclass Pdb.
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