ci(format): decide whether formatting warnings should fail validation #26

Summary

The CI Format step currently exits successfully even when swift-format reports style violations. The exact command reports 12 warnings and exits 0 at this revision; adding --strict makes the same check exit 1. Decide whether the step is advisory or an enforcing gate.

Code evidence at 5d4987b:

• .github/workflows/ci.yml:26 names the Format step; :27 runs swift-format lint without --strict.
• .swift-format:1 supplies the repository formatting configuration.
• Sources/Core/Installer.swift:165 and Sources/Core/RuntimeService.swift:1013 are examples of current warning locations.

Use Case

Contributors and reviewers need a clear contract for whether a green Format step means formatting conforms to the checked-in rules.

Reproduction / current-state verification

Executed at 5d4987b.

Run in Bash after cd "<checkout>" && swift build, replacing <checkout> with the absolute path of the checkout at this revision. Use a fresh reproduction directory. The commands isolate HOME, agent configuration, and XDG_*, and remove their fixture root on exit.

set -eu
checkout="<checkout>"
skill_bin="$checkout/.build/debug/skill"
repro_root="$checkout/.build/issue-repro-lint"
mkdir -p "$repro_root/home" "$repro_root/tmp" "$repro_root/project"
trap 'rm -rf "$repro_root"' EXIT
isolated() {
  env -i PATH="$PATH" HOME="$repro_root/home" \
    CODEX_HOME="$repro_root/home/.codex" \
    CLAUDE_CONFIG_DIR="$repro_root/home/.claude" \
    XDG_CONFIG_HOME="$repro_root/home/.config" \
    XDG_STATE_HOME="$repro_root/home/.local/state" \
    XDG_CACHE_HOME="$repro_root/home/.cache" TMPDIR="$repro_root/tmp" \
    GIT_CONFIG_NOSYSTEM=1 GIT_CONFIG_GLOBAL=/dev/null \
    GIT_AUTHOR_NAME=Fixture [email protected] \
    GIT_COMMITTER_NAME=Fixture [email protected] \
    "$@"
}
skill() { isolated "$skill_bin" "$@"; }
cd "$repro_root/project"

cd "$checkout"
set +e
isolated xcrun swift-format lint --configuration .swift-format --recursive Package.swift Sources Tests > "$repro_root/lint.log" 2>&1
printf 'CI lint exit: %s\n' "$?"
isolated xcrun swift-format lint --strict --configuration .swift-format --recursive Package.swift Sources Tests > "$repro_root/strict.log" 2>&1
printf 'strict lint exit: %s\n' "$?"
head -3 "$repro_root/lint.log"
printf 'warning count: '
grep -c 'warning:' "$repro_root/lint.log"

Observed output (relevant lines; temporary paths shortened to <temp>):

CI lint exit: 0
strict lint exit: 1
Sources/Core/Installer.swift:165:1: warning: [Indentation] indent by 2 spaces
Sources/Core/Installer.swift:166:1: warning: [Indentation] indent by 2 spaces
Sources/Core/RuntimeService.swift:1013:26: warning: [AddLines] add 1 line break
warning count: 12

Environment: Apple Swift 6.4, macOS 27.0.1 (26A434), arm64; CLI 0.2.1; validation date 2026-10-17.

Proposed Behavior

Maintainer decision: choose enforcement or explicitly advisory linting. If enforcing, use --strict (or an equivalent supported error policy), establish a clean baseline, and document the required local command. If advisory, label/document the CI step so warnings are not mistaken for a required style pass.

Completion checks:

• Verify the chosen exit policy with a small deliberate violation and with conforming code.
• CI and contributor instructions use the same policy and formatter/toolchain expectations.
• Handle existing warnings deliberately; do not introduce a broad suppression that hides new violations.

Tradeoffs

Strictness changes CI policy and requires addressing the existing warning baseline. An advisory step can still be useful; exit 0 on warnings is the formatter's documented local help behavior, not evidence of a malfunction.

Compatibility Notes

Executed with the Xcode formatter whose --version reports main; xcrun swift-format lint --help exposes --strict as treating findings as errors. Results may differ with another formatter version, so record/pin the supported toolchain when choosing the policy.

Related: PR #3, PR #11, and PR #12 report successful lint with existing warnings. None establishes an enforcement decision. No duplicate found.