fix(core/automerge): care only about automergeSchedule when branch exists (#23561)

Co-authored-by: HonkingGoose <34918129+HonkingGoose@users.noreply.github.com>
Co-authored-by: Rhys Arkins <rhys@arkins.net>

docs/usage/configuration-options.md

@@ -190,6 +190,10 @@ So for example you could choose to automerge all (passing) `devDependencies` onl
 }
 ```
 
+<!-- prettier-ignore -->
+!!! note
+    Branches creation follows [`schedule`](#schedule) and the automerge follows [`automergeSchedule`](#automergeschedule).
+
 <!-- prettier-ignore -->
 !!! warning "Negative reviews on GitHub block Renovate automerge"
     Renovate won't automerge on GitHub if a PR has a negative review.

lib/workers/repository/update/branch/index.spec.ts

@@ -610,6 +610,29 @@ describe('workers/repository/update/branch/index', () => {
       });
     });
 
+    // automerge should respect only automergeSchedule
+    // mock a case where branchPr does not exist, pr-creation is off-schedule, and the branch is configured for automerge
+    it('automerges when there is no pr and, pr-creation is off-schedule', async () => {
+      schedule.isScheduledNow.mockReturnValueOnce(false);
+      getUpdated.getUpdatedPackageFiles.mockResolvedValueOnce(
+        partial<PackageFilesResult>({
+          updatedPackageFiles: [partial<FileChange>()],
+        })
+      );
+      npmPostExtract.getAdditionalFiles.mockResolvedValueOnce({
+        artifactErrors: [],
+        updatedArtifacts: [partial<FileChange>()],
+      });
+      scm.branchExists.mockResolvedValue(true);
+      commit.commitFilesToBranch.mockResolvedValueOnce(null);
+      automerge.tryBranchAutomerge.mockResolvedValueOnce('automerged');
+      config.automerge = true;
+      config.automergeType = 'branch';
+      await branchWorker.processBranch(config);
+      expect(automerge.tryBranchAutomerge).toHaveBeenCalledTimes(1);
+      expect(prWorker.ensurePr).toHaveBeenCalledTimes(0);
+    });
+
     it('returns if branch automerged', async () => {
       getUpdated.getUpdatedPackageFiles.mockResolvedValueOnce(
         partial<PackageFilesResult>({

lib/workers/repository/update/branch/index.ts

@@ -309,8 +309,10 @@ export async function processBranch(
           result: 'update-not-scheduled',
         };
       }
-      // istanbul ignore if
+      if (
-      if (!branchPr) {
+        !branchPr &&
+        !(config.automerge && config.automergeType === 'branch') // if branch is configured for automerge there's no need for a PR
+      ) {
         logger.debug('Skipping PR creation out of schedule');
         return {
           branchExists,