Improve reliability for re-runs

Implements a recommendation that both Codex and Copilot gave to the PR.
They accurately pointed out that the results would be unpredictable and
unreliable in the case of multiple check runs with the same name (such
as reruns). This starts using only the most recent check run for each
name.

Author: russtaylor

dist/index.js

@@ -91,18 +91,26 @@ export async function requiredCheckRunLoopIteration(
     }
   )
 
+  // Track check runs by name, keeping only the most recent (highest ID) for each name.
+  // GitHub's Check Runs API can return multiple check runs with the same name
+  // (e.g., due to re-runs), and the order is not guaranteed to be deterministic.
   const foundChecks = new Map<
     string,
-    {status: string; conclusion: string | null}
+    {id: number; status: string; conclusion: string | null}
   >()
 
   for await (const response of checkRunsIterator) {
     for (const checkRun of response.data) {
       if (requiredCheckRuns.has(checkRun.name)) {
-        foundChecks.set(checkRun.name, {
-          status: checkRun.status,
-          conclusion: checkRun.conclusion
-        })
+        const existing = foundChecks.get(checkRun.name)
+        // Only update if this check run has a higher ID (more recent)
+        if (!existing || checkRun.id > existing.id) {
+          foundChecks.set(checkRun.name, {
+            id: checkRun.id,
+            status: checkRun.status,
+            conclusion: checkRun.conclusion
+          })
+        }
       }
     }
   }
@@ -449,10 +457,11 @@ async function checkRunLoopIteration(
   )
 
   let totalCheckRuns = 0
-  let filteredCheckRuns = 0
 
-  const pendingCheckRuns: PendingCheckRun[] = []
-  const completedCheckRuns: CompletedCheckRun[] = []
+  // Track check runs by name, keeping only the most recent (highest ID) for each name.
+  // GitHub's Check Runs API can return multiple check runs with the same name
+  // (e.g., due to re-runs), and the order is not guaranteed to be deterministic.
+  const checkRunsByName = new Map<string, CheckRun>()
 
   for await (const response of checkRunsIterator) {
     totalCheckRuns += response.data.length
@@ -462,18 +471,27 @@ async function checkRunLoopIteration(
         continue
       }
 
-      filteredCheckRuns++
-
-      if (isCheckRunCompleted(checkRun)) {
-        completedCheckRuns.push(checkRun)
-      } else {
-        pendingCheckRuns.push(checkRun)
+      const existing = checkRunsByName.get(checkRun.name)
+      // Only update if this check run has a higher ID (more recent)
+      if (!existing || checkRun.id > existing.id) {
+        checkRunsByName.set(checkRun.name, checkRun)
       }
     }
   }
 
+  const pendingCheckRuns: PendingCheckRun[] = []
+  const completedCheckRuns: CompletedCheckRun[] = []
+
+  for (const checkRun of checkRunsByName.values()) {
+    if (isCheckRunCompleted(checkRun)) {
+      completedCheckRuns.push(checkRun)
+    } else {
+      pendingCheckRuns.push(checkRun)
+    }
+  }
+
   core.info(
-    `Found ${totalCheckRuns} total check runs, keeping ${filteredCheckRuns}.`
+    `Found ${totalCheckRuns} total check runs, keeping ${checkRunsByName.size} unique.`
   )
 
   return [pendingCheckRuns, completedCheckRuns]