Add authoring-github-workflows skill + actionlint CI gate (prevent workflow-YAML breakage) by YuliiaKovalova · Pull Request #760 · dotnet/skills

YuliiaKovalova · 2026-06-12T14:41:53Z

Why

Eval on main broke for every run after #746 merged, with GitHub reporting "This run likely failed because of a workflow file issue" and no jobs starting. Root cause: an unquoted ${{ }} expression in run-name containing #. In YAML, # starts a comment, so the expression was silently truncated to ...format('Evaluate PR — an unterminated ${{. The file still parsed as valid YAML (so yaml.safe_load and review passed), but GitHub Actions rejected it.

This PR makes sure we never see that class of bug again, with two layers:

1. Knowledge — a skill

.agents/skills/authoring-github-workflows/SKILL.md (alongside the existing repo contributor meta-skills like create-skill) documents:

The #-as-comment trap and the quoting rule for expression scalars.
Other characters that force quoting.
Why YAML-only validation (yaml.safe_load, yamllint) is not enough — only actionlint understands the Actions expression grammar.
The failure signature ("workflow file issue", no jobs).

2. Enforcement — an actionlint CI gate

.github/workflows/actionlint.yml runs a pinned actionlint on every PR/push that touches .github/workflows/:

Lints only hand-authored workflows; generated gh-aw files (DO NOT EDIT headers, e.g. *.lock.yml, agentics-maintenance.yml) are skipped — they're compiled artifacts.
Runs with -shellcheck= -pyflakes= so the gate targets workflow/expression correctness, not pre-existing shell/Python style noise.
.github/actionlint.yaml declares the repo's custom runner labels (ubuntu-slim, windows-11-arm).

Verification

actionlint exits 0 on all 14 hand-authored workflows (including the fixed evaluation.yml).
Reverting the quote reproduces got unexpected EOF while lexing end of string literal [expression] and actionlint exits 1 — confirming the gate would have caught the original bug.

Note

This PR is stacked on #759 (the one-line evaluation.yml hotfix) so the new gate is green here. The fix commit is identical, so it merges cleanly whether #759 lands first or this PR does. If you prefer, merge #759 for the urgent fix and this PR for the durable prevention.

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com

…ment The run-name added in dotnet#746 is an unquoted plain scalar containing ` #{0}`. In YAML, a space followed by '#' starts a comment, so everything from '#{0} ...' onward was stripped, leaving an unterminated ${{ }} expression. The file still parses as YAML (yaml.safe_load succeeds) but GitHub Actions rejects it ("This run likely failed because of a workflow file issue"), which broke every evaluation run on main after dotnet#746 merged. Wrapping the value in double quotes keeps the full expression intact; verified with actionlint. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Prevents the class of bug that broke evaluation on main (dotnet#746): an unquoted `${{ }}` workflow expression containing `#`, which YAML treats as a comment and silently truncates, producing a file that parses as YAML but that GitHub Actions refuses to run ("This run likely failed because of a workflow file issue", no jobs started). Two layers: - Knowledge: .agents/skills/authoring-github-workflows/SKILL.md teaches the `#`-as-comment trap and other quoting rules, and to validate with actionlint (plain YAML linters accept the truncated form). - Enforcement: .github/workflows/actionlint.yml runs a pinned actionlint on hand-authored workflows for any PR/push touching .github/workflows. Generated gh-aw files (DO NOT EDIT headers) are skipped; shellcheck/pyflakes are off so the gate focuses on workflow/expression errors. .github/actionlint.yaml declares the repo's custom runner labels (ubuntu-slim, windows-11-arm). Verified locally: actionlint exits 0 on all hand-authored workflows, and exits 1 on the original unquoted run-name, confirming the gate catches it. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

github-actions · 2026-06-12T14:42:06Z

Note

This PR is from a fork and modifies infrastructure files (eng/ or .github/).

Changes to infrastructure typically need to be submitted from a branch in dotnet/skills (not a fork) so that CI workflows run with the correct permissions and secrets.

Please consider recreating this PR from an upstream branch. If you don't have push access to dotnet/skills, ask a maintainer to push your branch for you.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR prevents GitHub Actions workflow-YAML breakage from reaching main by documenting YAML-vs-Actions parsing traps and adding an actionlint CI gate, alongside a targeted fix to evaluation.yml’s run-name expression quoting.

Changes:

Quote evaluation.yml’s run-name expression so # can’t be interpreted as a YAML comment.
Add an actionlint workflow that lints hand-authored workflows on PRs/pushes.
Add actionlint configuration for custom runner labels and a new repository “skill” doc describing safe workflow authoring.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
`.github/workflows/evaluation.yml`	Quotes `run-name` expression to avoid YAML comment truncation.
`.github/workflows/actionlint.yml`	Adds CI gate to lint workflows with `actionlint`, skipping generated files.
`.github/actionlint.yaml`	Configures `actionlint` with repo-specific runner labels.
`.agents/skills/authoring-github-workflows/SKILL.md`	Documents common workflow authoring pitfalls and validation steps.

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github-actions · 2026-06-12T15:29:14Z

👋 @YuliiaKovalova — this PR has 3 unresolved review thread(s). When you're ready, please address the feedback and push an update; the triage bot will pick up the next state automatically. (Add the no-stale label to silence further pings.)

JanKrivanek

Thanks!

…ctic-vs-semantic scope Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

…eds, verify actionlint checksum Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

YuliiaKovalova · 2026-06-16T10:53:03Z

/evaluate

github-actions · 2026-06-16T10:53:50Z

⏭️ No skills to evaluate — no changed skills with tests were found in this PR. View workflow run

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

+          # excluded — they are compiled artifacts, not source we maintain.
+          to_lint=()
+          while IFS= read -r f; do
+            if head -n 30 "$f" | grep -qiE 'DO NOT EDIT|automatically generated|gh aw'; then


YuliiaKovalova and others added 2 commits June 12, 2026 16:26

Copilot AI review requested due to automatic review settings June 12, 2026 14:41

YuliiaKovalova requested review from JanKrivanek, ViktorHofer, dbreshears and timheuer as code owners June 12, 2026 14:41

Copilot started reviewing on behalf of YuliiaKovalova June 12, 2026 14:42 View session

Fix markdownlint MD038: remove spaces inside code spans in SKILL.md

4edcef0

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot AI reviewed Jun 12, 2026

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Comment thread .github/workflows/actionlint.yml

Comment thread .github/workflows/actionlint.yml Outdated

Comment thread .agents/skills/authoring-github-workflows/SKILL.md Outdated

github-actions Bot added the waiting-on-author PR state label label Jun 12, 2026

JanKrivanek approved these changes Jun 13, 2026

View reviewed changes

Comment thread .agents/skills/authoring-github-workflows/SKILL.md

Address PR review comments: actionlint config trigger, curl -f, synta…

ff6fdc4

…ctic-vs-semantic scope Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings June 16, 2026 09:32

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Copilot AI reviewed Jun 16, 2026

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Comment thread .github/workflows/actionlint.yml

Comment thread .github/workflows/actionlint.yml

YuliiaKovalova and others added 2 commits June 16, 2026 11:47

Harden actionlint workflow: pin checkout to SHA, disable persisted cr…

701a9d8

…eds, verify actionlint checksum Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Merge branch 'main' into skill/github-workflow-authoring

e853fac

Copilot AI review requested due to automatic review settings June 16, 2026 10:53

Copilot started reviewing on behalf of YuliiaKovalova June 16, 2026 10:53 View session

YuliiaKovalova merged commit 01b4875 into dotnet:main Jun 16, 2026
36 checks passed

Copilot AI reviewed Jun 16, 2026

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Comment thread .github/workflows/actionlint.yml

# excluded — they are compiled artifacts, not source we maintain.

to_lint=()

while IFS= read -r f; do

if head -n 30 "$f" | grep -qiE 'DO NOT EDIT|automatically generated|gh aw'; then

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Add authoring-github-workflows skill + actionlint CI gate (prevent workflow-YAML breakage) - #760

Add authoring-github-workflows skill + actionlint CI gate (prevent workflow-YAML breakage)#760
YuliiaKovalova merged 6 commits into
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YuliiaKovalova:skill/github-workflow-authoring

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YuliiaKovalova commented Jun 12, 2026

Why

1. Knowledge — a skill

2. Enforcement — an actionlint CI gate

Verification

Note

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