gh-132502: Implements PEP-830 adding timestamps to tracebacks by gpshead · Pull Request #129337 · python/cpython
added 24 commits
This came up at work as a suggestion to make debugging what happened in big async servers with lots of exception groups and exceptions easier. Timestamps when emitting exception groups containing tracebacks often with their own nested causes would allow some semblance of order to be understood. This is a demo. If we want such a feature, we should settle on semantics in a Discuss thread and write it up as a PEP. This should be simpler than exception notes (PEP-678) was. One thought was just to store the timestamp as a note; but that'd involve string and list creation on every exception. Performance testing needs to be done. This is the kind of thing that is visually distracting, so not all applications want to _see_ the timestamps. A knob to turn that on for those who do seems more useful rather than making that the default. But the performance impact of merely collecting the timestamps is worth knowing.
Avoids a 15% regression in the pyperformance async_generators suite.
Tested with `PYTHON_TRACEBACK_TIMESTAMPS=ns` set. First pass. Further review could rework some of these changes. Explicit tests for the new feature have yet to be added.
Better docs, improved tests. Claude Code using Sonnet 3.7 helped with this, but that was a bit of a battle as our CPython code context size for this type of change is huge.
TODO: performance testing - this increases the conditional load on every BaseException instantiation with that interp->config.field && field[0] check. If needed, we could cache the "collect or not" bool in a static global as it is fair to say this is a process wide setting rather than per interpreter, but ugh.
… other processes in tests as well
gh-132502: Implements PEP-829 adding timestamps to tracebacks
gh-132502: Implements PEP-830 adding timestamps to tracebacks
Resolve conflicts in Lib/subprocess.py (adopt generic sorted xoptions loop) and Objects/exceptions.c (integrate _PyTuple_FromPair with timestamp-aware __reduce__ methods).
Updates the implementation to match the PEP revisions in python/peps#4928 * Drop the ``us`` display format; ``-X traceback_timestamps`` with no value or ``=1`` now selects ``ns``. * ``ns`` format now renders as seconds with nine fractional digits (``<@1776017178.687320256>``) instead of a raw integer with an ``ns`` suffix. Integer divmod is used to preserve full precision. * The ``no_timestamp`` boolean on the traceback formatting APIs is replaced by a tri-state ``timestamps`` keyword: ``None`` follows the global config, ``False`` suppresses, ``True`` forces display of any non-zero ``__timestamp_ns__``. The setting now propagates through ``__cause__``, ``__context__`` and exception-group members. * MemoryError instances handed out from the free list receive a fresh timestamp at hand-out time; only the last-resort static singleton remains at 0.