Add SwiftFormat lint check on pull requests#599
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marionbarker merged 2 commits intodevfrom Apr 26, 2026
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Runs swiftformat --lint in a Linux container on every PR using the same BuildTools pin (SwiftFormat 0.56.1) and flags as the local Scripts/swiftformat.sh, so CI stays in sync with `swift run swiftformat` on a developer machine. Fails the check on any violation without rewriting files — contributors fix formatting themselves and push, rather than having CI commit back over their branch. BuildTools/.build is cached by Package.resolved hash to keep subsequent runs fast.
Adds a concurrency group so rapid successive pushes to a PR branch don't stack up multiple Lint runs — the in-progress run is cancelled as soon as a newer commit arrives.
marionbarker
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Apr 26, 2026
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Looks good from code review and was tested with this throw-away PR.
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Adds a
Lintworkflow that runsswiftformat --linton every pull request.What it does
ubuntu-latestinside the officialswift:6.0container — no macOS minutes consumed.BuildTools/Package.swiftso the CI version is always the same pin developers use locally (currently0.56.1). No separate config to drift.--headerand--excludeflags asScripts/swiftformat.sh, so whatever passes locally passes in CI.--lintmode: reports violations and exits non-zero without rewriting any files. The PR check goes red; the contributor runsswiftformatlocally and pushes the fix themselves. CI never commits back over a contributor's branch.BuildTools/.buildis cached byPackage.resolvedhash — first run compiles SwiftFormat (~2–3 min), subsequent runs are <30s.Why not auto-fix and commit back
GITHUB_TOKENcan't push to fork PRs, so any auto-fix path requires a PAT with push rights — a real security footgun for a lint job.git blameand commit authorship get muddied by bot commits.Enabling as a required check
The workflow only reports status. To actually block merges on lint failures, the check needs to be marked Required in branch protection (Settings → Branches →
dev→ "Require status checks to pass before merging" → addLint / SwiftFormat). GitHub only lets you require checks it has seen run at least once, so this should be done after the first successful run on this PR.