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Merge pull request #136 from script-development/ci/crier-2approval-consensus
ci(town-crier): auto-resolve bus thread on 2-approval consensus
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‎.github/workflows/announce-pr.yml‎

Lines changed: 72 additions & 12 deletions
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# - Variable TOWN_CRIER_URL = https://<app>.fly.dev
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# - Secret TOWN_CRIER_TOKEN = the bearer token minted for "github-action"
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#
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# Produces BOTH sides of a request's lifecycle, so the bus never drifts from GitHub:
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# - announce: when "Agent Review Requested" lands on a PR, tell the crier once.
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# - resolve: when that PR closes/merges or its review label is removed, retire its
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# thread — otherwise a landed PR sits "open" on the bus forever (there is
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# no GitHub->bus merge sync).
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# Produces the FULL lifecycle of a request, so the bus never drifts from GitHub:
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# - announce: "Agent Review Requested" lands on a PR (or a new commit is pushed) -> tell the crier.
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# - resolve (close): the PR closes/merges or its review label is removed -> retire its thread.
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# - resolve (consensus): a 2nd independent approval lands with no outstanding change request -> retire the
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# thread; consensus is reached, so further review turns are just churn.
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# Without these a landed/settled PR sits "open" on the bus forever (there is no GitHub->bus merge sync).
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# The consensus job counts only approvals cast at the CURRENT head, so a stale approval from an earlier push
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# can't satisfy consensus on a reopened thread — robust regardless of the repo's dismiss-stale-reviews setting.
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# The bus never stores approval state; the job reads the live count and calls the EXISTING resolve verb.
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# Joined harnesses pick up open requests from the bus — this workflow does NOT poll or review.
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#
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# Failure policy (two distinct modes, so a real problem is never silently masked):
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# - MISSING provisioning (no TOWN_CRIER_URL/TOKEN) is a config error -> fail LOUD (red).
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# - A bus HICCUP (cold start / transient 5xx / timeout) -> ::warning:: + stay GREEN (fail-open;
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# a coordination-layer blip must never red a contributor's PR checks).
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# Neither job uses the GITHUB_TOKEN (they auth to the bus with TOWN_CRIER_TOKEN), so permissions
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# are dropped to nothing.
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name: town-crier producer (announce + resolve)
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# - A bus HICCUP (cold start / transient 5xx / timeout) or an unreadable review list -> ::warning:: +
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# stay GREEN (fail-open; a coordination-layer blip must never red a contributor's PR checks).
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# The announce/resolve jobs use no GITHUB_TOKEN (they auth to the bus with TOWN_CRIER_TOKEN); the consensus
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# job needs pull-requests:read to count approvals, granted at job scope only.
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name: town-crier producer (announce + resolve + consensus)
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permissions: {}
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on:
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pull_request:
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# labeled -> first announce; synchronize -> re-announce each new commit (re-review on push);
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# closed/unlabeled -> resolve (de-announce). A synchronize on an unlabelled PR is ignored by the if.
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# labeled -> first announce; synchronize -> re-announce each new commit (re-review on push);
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# unlabeled/closed -> resolve (de-announce). A synchronize on an unlabelled PR is ignored by the if.
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types: [labeled, synchronize, unlabeled, closed]
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pull_request_review:
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# submitted -> a review landed; the consensus job checks whether 2 independent approvals now agree.
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types: [submitted]
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jobs:
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announce:
@@ -93,3 +100,56 @@ jobs:
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-H "Content-Type: application/json" \
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-d "$(jq -n --arg pr "$PR_URL" --arg note "$NOTE" '{pr_url:$pr, note:$note}')" \
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|| echo "::warning::town-crier resolve failed (transient bus issue?) — not blocking the PR"
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consensus:
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# A review landed — if it's an approval on a labelled PR, retire the bus thread once TWO independent
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# approvals agree with no outstanding change request. We read the live count (filtered to the current
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# head, so stale approvals can't satisfy consensus) rather than tracking it on the bus.
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if: >-
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github.event.review.state == 'approved' &&
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contains(github.event.pull_request.labels.*.name, 'Agent Review Requested')
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runs-on: ubuntu-latest
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permissions:
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pull-requests: read # read the PR's reviews to count approvals (GITHUB_TOKEN, this job only)
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steps:
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- name: Resolve on consensus
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env:
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CRIER_URL: ${{ vars.TOWN_CRIER_URL }}
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CRIER_TOKEN: ${{ secrets.TOWN_CRIER_TOKEN }}
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GH_TOKEN: ${{ github.token }}
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REPO: ${{ github.repository }}
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PR_NUMBER: ${{ github.event.pull_request.number }}
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PR_URL: ${{ github.event.pull_request.html_url }}
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HEAD_OID: ${{ github.event.pull_request.head.sha }}
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run: |
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if [ -z "$CRIER_URL" ] || [ -z "$CRIER_TOKEN" ]; then
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echo "::error::town-crier not provisioned — set the TOWN_CRIER_URL variable + TOWN_CRIER_TOKEN secret"
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exit 1
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fi
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# Tally the LATEST opinionated review per reviewer (ignore COMMENTED/PENDING), counting an
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# approval ONLY if it was cast at the CURRENT head — a stale approval from an earlier push must
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# not satisfy consensus on a reopened thread (correct regardless of dismiss_stale_reviews).
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# NDJSON via --paginate --jq '.[]' then slurp with jq -s — avoids `gh api --slurp` (newer-gh only).
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tally="$(gh api --paginate "repos/$REPO/pulls/$PR_NUMBER/reviews" --jq '.[]' \
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| jq -s --arg head "$HEAD_OID" '
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map(select(.state == "APPROVED" or .state == "CHANGES_REQUESTED" or .state == "DISMISSED"))
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| group_by(.user.login) | map(max_by(.submitted_at))
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| {approved: (map(select(.state == "APPROVED" and .commit_id == $head)) | length),
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changes: (map(select(.state == "CHANGES_REQUESTED")) | length),
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who: (map(select(.state == "APPROVED" and .commit_id == $head)) | map(.user.login) | join(", "))}' \
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)" || { echo "::warning::could not read PR reviews (transient?) — not blocking the PR"; exit 0; }
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approved="$(printf '%s' "$tally" | jq -r '.approved')"
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changes="$(printf '%s' "$tally" | jq -r '.changes')"
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who="$(printf '%s' "$tally" | jq -r '.who')"
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echo "approvals=$approved changes_requested=$changes approvers=[$who]"
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# Consensus = >= 2 distinct CURRENT-HEAD approvals AND no outstanding change request.
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if [ "${approved:-0}" -lt 2 ] || [ "${changes:-0}" -ne 0 ]; then
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echo "no consensus yet — leaving the thread open for another turn"
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exit 0
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fi
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NOTE="consensus: ${approved} approvals (${who}) @${HEAD_OID:0:12}"
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curl -fsS --max-time 10 -X POST "$CRIER_URL/resolve" \
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-H "Authorization: Bearer $CRIER_TOKEN" \
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-H "Content-Type: application/json" \
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-d "$(jq -n --arg pr "$PR_URL" --arg note "$NOTE" '{pr_url:$pr, note:$note}')" \
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|| echo "::warning::town-crier consensus-resolve failed (transient bus issue?) — not blocking the PR"

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