test(spec): verify portable parser settings

[jdx]

_{Stack created with GitHub Stacks CLI • Give Feedback 💬}

---

Note

Low Risk
Test-only changes and a dev-dependency; no production parsing or spec behavior is modified.

Overview
Adds an integration test on the usage-rs facade that derive-emitted KDL keeps parser settings such as unknown_flags = "error" as portable spec metadata, not just runtime behavior.

The test defines a strict CLI (StrictEx), asserts unknown flags fail at parse time, checks the generated KDL includes unknown_flags "error", and round-trips that KDL through usage-lib to confirm Spec.unknown_flags is Error. usage-lib is wired in as a dev-dependency only for this assertion.

^{Reviewed by Cursor Bugbot for commit 40b369d. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Central YAML (base), Organization UI (inherited)

Review profile: CHILL

Plan: Pro Plus

Run ID: ff98e51d-7b14-4ac6-954b-6ace950377b6

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[github-actions]

Instruction counts

benchmark	trend	instructions	Δ	wall (min)	Δ
markdown	▂▂▃▂▂▃▃▃▁█▇██	198,800,919 → 198,849,216	+0.02%	18.77 → 18.68ms	-0.50%
startup	▁▁▁▁▁▁▁▁▁████	1,214,930 → 1,214,934	+0.00%	1.25 → 1.29ms	+3.57%

No instruction-count regression above 1%.

_{Only instruction counts gate. Wall clock is shown for context — on identical hardware it moves 4-20% run to run.}

_{Measured by tak — instruction-counted CLI benchmarks, stored in this repository's git notes.}

Shadow comparison

Parsing mise use -g node@20 against a shadow of mise's committed spec.
Reported, not gated: the shadow grows as the derive learns to express more, so
what to watch is the ratio rather than either column.

framework	instructions, cold parse	vs usage
usage	4253	—
argh	6292	1.5x
clap	5893640	1385x
bpaf	21917948	5153x

                                              min       p01       p10    median
usage-rs: argv -> struct                      191       194       198       207  ns
argh: argv -> struct                          272       276       281       289  ns
clap: build tree + parse -> struct         484240    485132    486684    489281  ns
bpaf: build parser + parse -> struct      1611270   1611270   1619372   1707026  ns

usage: argv -> struct                             204 ns      0.20 µs
clap: build tree + parse -> struct             490573 ns    490.57 µs
clap: parse -> struct, tree reused              23587 ns     23.59 µs
clap: build tree only                          299719 ns    299.72 µs

_{40b369d49c56 vs 93ea42d8d54e · measured on the runner, not pushed to the history.}