From 0d9bd0091eb8d4cf4f80e007fd661e8334e3bf32 Mon Sep 17 00:00:00 2001
From: "Benjamin R. J. Schwedler" <ben@posit.co>
Date: Mon, 8 Jun 2026 14:04:40 -0500
Subject: [PATCH] Notify on failure when no run history exists
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The action previously skipped silently when no previous workflow
runs were found on main. This prevented merge queue failures from
triggering notifications, since merge queue runs land on ephemeral
refs and never appear in a main-branch run query.

Now: no history + failed → fire failure notification; no history +
passed → skip. State-transition logic is unchanged for builds with
history.
---
 .github/actions/slack-build-notify/action.yml | 52 ++++++++++---------
 1 file changed, 28 insertions(+), 24 deletions(-)

diff --git a/.github/actions/slack-build-notify/action.yml b/.github/actions/slack-build-notify/action.yml
index efccfdecc..55ffb0eff 100644
--- a/.github/actions/slack-build-notify/action.yml
+++ b/.github/actions/slack-build-notify/action.yml
@@ -54,32 +54,36 @@ runs:
               .filter(r => r.id !== context.runId && r.conclusion !== 'cancelled')
               .sort((a, b) => new Date(b.created_at) - new Date(a.created_at));
 
-            if (previousRuns.length === 0) {
-              core.info('No previous completed runs found, skipping notification');
-              return;
-            }
-
-            const previousRun = previousRuns[0];
             const currentFailed = currentResult !== 'success';
 
-            // Compare against the previous run's CI job conclusion (not the workflow
-            // conclusion) so that clean-job flaps don't trigger false notifications.
-            // Falls back to workflow conclusion if the CI job isn't found.
-            const { data: { jobs: prevJobs } } = await github.rest.actions.listJobsForWorkflowRun({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              run_id: previousRun.id,
-              per_page: 100,
-            });
-            const prevCiJob = prevJobs.find(j => j.name === 'CI');
-            const previousConclusion = prevCiJob
-              ? prevCiJob.conclusion
-              : previousRun.conclusion;
-            const previousFailed = previousConclusion !== 'success';
-
-            if (currentFailed === previousFailed) {
-              core.info(`No state transition (current: ${currentResult}, previous: ${previousConclusion}), skipping`);
-              return;
+            if (previousRuns.length === 0) {
+              if (!currentFailed) {
+                core.info('No previous completed runs found and build passed, skipping notification');
+                return;
+              }
+              // No history — notify on failure directly (e.g. merge queue runs on ephemeral refs)
+            } else {
+              const previousRun = previousRuns[0];
+
+              // Compare against the previous run's CI job conclusion (not the workflow
+              // conclusion) so that clean-job flaps don't trigger false notifications.
+              // Falls back to workflow conclusion if the CI job isn't found.
+              const { data: { jobs: prevJobs } } = await github.rest.actions.listJobsForWorkflowRun({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                run_id: previousRun.id,
+                per_page: 100,
+              });
+              const prevCiJob = prevJobs.find(j => j.name === 'CI');
+              const previousConclusion = prevCiJob
+                ? prevCiJob.conclusion
+                : previousRun.conclusion;
+              const previousFailed = previousConclusion !== 'success';
+
+              if (currentFailed === previousFailed) {
+                core.info(`No state transition (current: ${currentResult}, previous: ${previousConclusion}), skipping`);
+                return;
+              }
             }
 
             const runUrl = currentRun.html_url;