feat: warn when running on an unsupported Python version

[not-matthias]

Print a warning in the pytest header when the running interpreter is outside the
Python version range pytest-codspeed claims to support:

WARNING: Python 3.16 is not officially supported by pytest-codspeed (supported:
3.9 to 3.15). Support is experimental and untested, measurements may be unreliable.

Customers upgrading Python currently get silent, unvalidated measurements: nothing
tells them the interpreter they benchmark on was never tested. Surfacing it in the
header means it lands in the CI log right under the existing codspeed: <version>
line, next to the other notices.

The bounds live in pytest_codspeed.utils and mirror requires-python plus the
Programming Language :: Python classifiers in pyproject.toml and the CI matrix.
The issue did not specify a list, and the sources disagreed: the classifiers and CI
say 3.15, while the README badge says 3.14 and the docs badge 3.13. The badges are
stale (docs still claimed 3.13 well after 3.14 classifiers shipped), so the bounds
follow the classifiers. Warning on 3.15 would contradict the package's own metadata
and redden the 3.15 CI legs.

test_get_python_version_warning_supported asserts no warning fires on the
interpreter running the suite, so adding a Python version to the CI matrix without
bumping the constant fails loudly instead of silently warning users.

Not included: the "warning on the Run page" half of the issue is platform-side. The
plugin already ships full interpreter metadata via get_environment_metadata and
collect_and_write_python_environment, so no extra plumbing is needed here.

Refs COD-3400

[codspeed-hq]

Merging this PR will regress 7 benchmarks

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 12 improved benchmarks
❌ 7 regressed benchmarks
✅ 203 untouched benchmarks
⏩ 55 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	WallTime	test_recursive_fibo_20	5.3 ms	5.9 ms	-9.39%
❌	WallTime	test_noop_lambda_decorated	1.3 µs	1.3 µs	-4.87%
❌	WallTime	test_mmap_operation[409600]	128.5 µs	135.1 µs	-4.85%
❌	Memory	test_multiprocessing_map[100]	3.2 MB	3.4 MB	-3.83%
❌	WallTime	test_generate_sum_of_subsets_soln[nums0-9]	26.1 µs	27.1 µs	-3.54%
❌	WallTime	test_noop_pass_decorated	658.4 ns	680.7 ns	-3.27%
❌	WallTime	test_tcp_connection[1.1.1.1-53]	948.1 µs	973.5 µs	-2.6%
⚡	WallTime	test_multiprocessing_map[100000]	419.4 ms	320.6 ms	+30.83%
⚡	WallTime	test_multiprocessing_map[1000]	59.2 ms	51 ms	+16.01%
⚡	Memory	test_multiprocessing_map[10]	4.1 MB	3.6 MB	+13.73%
⚡	Memory	test_multiprocessing_map[10000]	3.4 MB	3.1 MB	+9.28%
⚡	Memory	test_multiprocessing_map[100000]	6.2 MB	5.7 MB	+8.93%
⚡	WallTime	test_sum_of_squares[sum_of_squares_sum_labmda_power]	350.4 µs	325.7 µs	+7.59%
⚡	Memory	test_multiprocessing_map[1000]	3.7 MB	3.5 MB	+5.86%
⚡	WallTime	test_get_valid_pos[pos0-4]	2.9 µs	2.7 µs	+4.98%
⚡	WallTime	test_sum_of_squares[sum_of_squares_sum_comprehension_power]	238.5 µs	230.7 µs	+3.4%
⚡	WallTime	test_solve_maze[maze0]	24.8 µs	24.1 µs	+3.09%
⚡	WallTime	test_make_highpass	5.5 µs	5.4 µs	+2.91%
⚡	WallTime	test_open_close_fd[100]	901.6 µs	876.9 µs	+2.81%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing cod-3400-warn-when-running-pytest-codspeed-with-unsupported-python (4e49265) with master (c7e9981)}

Footnotes

1. 55 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[not-matthias]

@greptileai review

[greptile-apps]

Greptile Summary

The PR adds a pytest-header notice when the active interpreter falls outside the supported Python 3.9–3.15 range.

• Defines supported-version bounds and formats local or GitHub Actions warnings.
• Adds unit and pytest integration coverage for supported, unsupported, and annotation output.

Confidence Score: 5/5

The PR appears safe to merge because no blocking failure remains.

No blocking failure remains.

Important Files Changed

Filename	Overview
src/pytest_codspeed/plugin.py	Adds supported-version bounds, warning formatting, and inclusion of the warning in pytest's report header.
tests/test_pytest_plugin.py	Adds tests for supported and unsupported versions, GitHub Actions annotations, and header integration.

_{Reviews (2): Last reviewed commit: "feat: warn when running on an unsupporte..." | Re-trigger Greptile}

[greptile-apps]

ANSI ignores color settings

On an unsupported interpreter outside GitHub Actions, format_ci_warning embeds ANSI sequences even when pytest uses --color=no or writes to redirected output, leaving terminal-control bytes in non-color logs.

Knowledge Base Used: Validation and benchmark fixtures

Prompt To Fix With AI

This is a comment left during a code review.
Path: src/pytest_codspeed/utils.py
Line: 75

Comment:
**ANSI ignores color settings**

On an unsupported interpreter outside GitHub Actions, `format_ci_warning` embeds ANSI sequences even when pytest uses `--color=no` or writes to redirected output, leaving terminal-control bytes in non-color logs.

**Knowledge Base Used:** [Validation and benchmark fixtures](https://app.greptile.com/codspeed/-/custom-context/knowledge-base/codspeedhq/pytest-codspeed/-/docs/validation-and-benchmark-fixtures.md)

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!