gh-135751: traceback: add recent_first and show_lines parameter

[methane]

• Issue: traceback: add recent_first and show_lines parameters #135751

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📚 Documentation preview 📚: https://cpython-previews--135752.org.readthedocs.build/

[Copilot]

Pull Request Overview

Adds two new keyword-only parameters, show_lines and recent_first, to the traceback module’s formatting and printing APIs, allowing callers to suppress source lines or invert traceback order.

• Introduce show_lines and recent_first across module-level functions and TracebackException/StackSummary methods
• Update internal printing/formatting logic to pass these flags through
• Extend tests and documentation to cover new behavior

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Misc/NEWS.d/next/Library/2025-06-20-21-16-32…rst	Announce new parameters in the NEWS file
Lib/traceback.py	Core implementation: API signatures and logic updates
Lib/test/test_traceback.py	New unit tests for show_lines and recent_first flags
Doc/whatsnew/3.15.rst	Document what’s new section for show_lines/recent_first
Doc/library/traceback.rst	Update function/method docstrings to include new flags

Comments suppressed due to low confidence (4)

Lib/traceback.py:31

• The first line of the docstring was truncated and now only mentions extract_stack(). It should refer to both extract_tb() and extract_stack(), e.g., "Print the list of tuples as returned by extract_tb() or extract_stack() as a formatted stack trace to the given file."

    extract_stack() as a formatted stack trace to the given file.

Doc/whatsnew/3.15.rst:181

• [nitpick] Grammar in release notes: replace "It is default to True." with "Defaults to True." for clarity.

  It is default to ``True``.

Doc/library/traceback.rst:125

• [nitpick] This sentence is duplicated immediately above; remove one instance to avoid redundancy.

   If *show_lines* is false, source code lines are not included in the output.

Doc/library/traceback.rst:175

• [nitpick] Using "next" as a version string may be confusing. Consider using the actual upcoming version number or a placeholder like "3.x" for clarity.

   .. versionchanged:: next

[brianschubert]

I'm not sure this needs the loudness of a .. note block. Merging this into the previous paragraph would be sufficient IMO

[brianschubert]

nit: some of new version changed directives use the style "Added X parameter" while others use "Added the X parameter". Both styles are used elsewhere in the docs, but it would probably be better to use one consistently here

[brianschubert]

Suggested change

	The keyword argument *show_lines*, if ``False``, prevents source code
	lines from being included in the output.
	If *show_lines* is set to ``False``, source code lines will not be
	included in the output.

[hugovk]

Or flip to remove double negative.

[iritkatriel]

I think show_lines should be renamed to something like show_source.

[iritkatriel]

Why not add the new args via **kwargs as was done for colorize? It would save having to update all the signatures.

[methane]

I think colorize is in kwargs because of its hidden parameter. Callars determine use COLOR automatically by isatty() and env variables and pass it to here. colorize is not documented.

On the other hand, show_lines and recent_first are explicit parameter.
User need to determine and specify them manually.