[Python-ideas] Logical tracebacks

[Christian Heimes]

On 15/04/2019 22.07, Antoine Pitrou wrote:
> 
> Hello,
> 
> I apologize because I'm only going to throw a very vague idea and I
> don't currently have time or motivation to explore it myself.  But I
> think it may prove interesting for other people and perhaps spur some
> concrete actionable proposal.
> 
> With the growing complexity of Python software stacks, the length of
> tracebacks is continuously growing and is frequently making debugging
> errors and issues more tedious than it should be.  This is a
> language-agnostic problem.  Java software is often mocked for its
> ridiculously long tracebacks, but Python might come close in the future.
> 
> Especially since Python is often the a language of choice for non
> computer science professionals, including but not only as a teaching
> language, this would be a problem worth solving.  We already recognized
> the issue some years ago, and even implemented a focussed fix for one
> specific context: the elision of importlib frames when an import error
> occurs:
> https://bugs.python.org/issue15110
> 
> However, there are many contexts where implementation details would
> benefit from being hidden from tracebacks (the classical example being
> the internals of framework or middleware code, such as Django, Dask,
> etc.).  We would therefore have to define some kind of protocol by
> which tracebacks can be enumerated, not only as frames, but as logical
> execution blocks, comprised of one or several frames each, whose
> boundaries would reflect the boundaries of the various logical
> execution layers (again: framework, middleware...) involved in the
> frame stack.  We would probably also need some flag(s) to disable the
> feature in cases where the full stack frame is wanted (I imagine
> elaborate UIs could also allow switching back and forth from both
> representations).
> 
> This would need a lot more thinking, and perhaps exploring what kind of
> hacks already exist in the wild to achieve similar functionality.
> Again, I'm just throwing this around for others to play with.

Zope has a feature like that for more than a decade. Code could define
variables __traceback_info__  and __traceback_supplement__ in local
scope, which would then be used by the traceback formatter to annotate
the traceback with additional information. I think it was also possible
to hide frame with a similar technique.

https://zopeexceptions.readthedocs.io/en/latest/narr.html