fix: waitOnContentHash should also trigger on completed hash (#4718)

Prior to flipping completely over; we need to trigger tests for all
shas, even if the content hash was generated.

Author: jtmcdole

app_dart/lib/src/service/scheduler.dart

@@ -672,10 +672,14 @@ $s
       // TODO: MergeQueueHashStatus
       //   - .build: trigger targets!
       //   - .wait: something is building.
+      //   - .completed: hash already built, complete!
       //   - .*: do nothing
-      // FOR NOW: trigger builds for build/wait
+      // FOR NOW: trigger builds for build/wait/completed because they are also
+      //          building for SHA.
       switch (artifactStatus) {
-        case MergeQueueHashStatus.build || MergeQueueHashStatus.wait
+        case MergeQueueHashStatus.build ||
+                MergeQueueHashStatus.wait ||
+                MergeQueueHashStatus.complete
             when _config.flags.contentAwareHashing.waitOnContentHash:
           // Note from codefu: We do not have the merge queue lock yet.
           // It was short-circuited if the waitOnContentHash is set. The

app_dart/test/service/scheduler/hash_workflow_test.dart

@@ -191,6 +191,40 @@ void main() async {
       ),
     ).called(1);
   });
+
+  test(
+    'triggers tests on waitOnContentHash + completed artifacts (PRE-CAH flip over)',
+    () async {
+      config.dynamicConfig = DynamicConfig.fromJson({
+        'contentAwareHashing': {'waitOnContentHash': true},
+      });
+
+      final job = workflowJobTemplate().toWorkflowJob();
+
+      firestore.putDocument(
+        ContentAwareHashBuilds(
+          createdOn: DateTime(2025, 05, 20),
+          contentHash: '65038ef4984b927fd1762ef01d35c5ecc34ff5f7',
+          commitSha: 'a' * 40,
+          buildStatus: BuildStatus.success,
+          waitingShas: [],
+        ),
+      );
+
+      await scheduler.processWorkflowJob(job);
+
+      verify(
+        mockGithubChecksUtil.createCheckRun(
+          any,
+          RepositorySlug.full('flutter/flutter'),
+          '27bfdee25949bc48044c4e16678f3449dd213b6e',
+          'Merge Queue Guard',
+          output: anyNamed('output'),
+          conclusion: anyNamed('conclusion'),
+        ),
+      ).called(1);
+    },
+  );
 }
 
 extension on String {