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Case study: click COLUMNS

No upstream issue was found for this one. It is a found-in-the-wild failure on pallets/click (17.8k stars) at 06b2a67 (main): tests/test_commands.py::test_custom_parser fails whenever the COLUMNS environment variable is small, and passes with a wide or unset one. Someone with a 40-column terminal (or a CI job that exports COLUMNS) sees a red test that a maintainer cannot see.

The test builds an optparse.OptionParser and compares its format_help() output with fixed, 78-column-wrapped text. optparse sizes its help to COLUMNS, so the wrapping (and the test) changes with it.

File What it is
narrow-40.json capsule from a reporter with COLUMNS=40: the test fails
wide-120.json capsule from a maintainer with COLUMNS=120: the whole file passes
replay.txt twin replay narrow-40.json on Solari, recorded 2026-09-29
bisect.txt twin bisect narrow-40.json --good wide-120.json on Solari, recorded 2026-09-29
fix.patch candidate fix for the test
verify.txt twin verify narrow-40.json --patch fix.patch on Solari, recorded 2026-09-29

This is a Python project: uv (uv.lock), Python 3.13.12, uv 0.11.3, clean working tree at the commit. Capsules were captured with LANG=C.UTF-8, no LC_*, NO_COLOR=1, and --include-env COLUMNS (twin records most variable values by name only; COLUMNS is not in its shared-value list, so the reporter opts in to sharing it).

What happened

Section titled “What happened”

Capture:

uv run --frozen pytest -q -p no:cacheprovider tests/test_commands.py

twin diff wide-120.json narrow-40.json shows a single difference: COLUMNS 120 -> 40.

Command Verdict Wall time
twin replay narrow-40.json REPRODUCED (3 of 3 attempts, same signature) 20 s
twin bisect narrow-40.json --good wide-120.json minimal difference COLUMNS=40 25 s
twin verify narrow-40.json --patch fix.patch FIXED (3 of 3 attempts pass) 19 s

fix.patch passes optparse.IndentedHelpFormatter(width=78) (optparse’s own default for an 80-column terminal) so the expected text no longer depends on the terminal. The file passes locally with COLUMNS set to 40, 80, 200 and unset.

Run it yourself

Section titled “Run it yourself”
export SOLARI_API_KEY=...
twin replay examples/click-test-columns/narrow-40.json
twin bisect examples/click-test-columns/narrow-40.json --good examples/click-test-columns/wide-120.json
twin verify examples/click-test-columns/narrow-40.json --patch examples/click-test-columns/fix.patch

Every file referenced here is in examples/click-test-columns.