fix: don't reuse branch if results change (renovatebot#37083)

Co-authored-by: Rhys Arkins <rhys@arkins.net>

Author: RahulGautamSingh

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

@@ -933,6 +933,38 @@ describe('workers/repository/update/branch/index', () => {
       expect(prWorker.ensurePr).toHaveBeenCalledTimes(0);
     });
 
+    it('updates branch when forceRebase=true', async () => {
+      expect.assertions(3);
+      getUpdated.getUpdatedPackageFiles.mockResolvedValueOnce(
+        partial<PackageFilesResult>({
+          updatedPackageFiles: [partial<FileChange>()],
+        }),
+      );
+      npmPostExtract.getAdditionalFiles.mockResolvedValueOnce({
+        artifactErrors: [],
+        updatedArtifacts: [partial<FileChange>()],
+      });
+      const inconfig = {
+        ...config,
+        ignoreTests: true,
+        prCreation: 'not-pending',
+        commitBody: '[skip-ci]',
+        fetchChangeLogs: 'branch',
+        cacheFingerprintMatch: 'no-match',
+      } satisfies BranchConfig;
+      scm.getBranchCommit.mockResolvedValue('123test' as LongCommitSha); //TODO:not needed?
+      expect(await branchWorker.processBranch(inconfig, true)).toEqual({
+        branchExists: true,
+        updatesVerified: true,
+        prNo: undefined,
+        result: 'pending',
+        commitSha: '123test',
+      });
+
+      expect(automerge.tryBranchAutomerge).toHaveBeenCalledTimes(0);
+      expect(prWorker.ensurePr).toHaveBeenCalledTimes(0);
+    });
+
     it('ensures PR and comments notice', async () => {
       getUpdated.getUpdatedPackageFiles.mockResolvedValueOnce(
         partial<PackageFilesResult>({
@@ -1350,6 +1382,79 @@ describe('workers/repository/update/branch/index', () => {
       expect(prWorker.ensurePr).toHaveBeenCalledTimes(1);
     });
 
+    it('rebases branch onto new basebranch if no fingerprint found', async () => {
+      const updatedPackageFile: FileChange = {
+        type: 'addition',
+        path: 'pom.xml',
+        contents: 'pom.xml file contents',
+      };
+      const pr = partial<Pr>({
+        state: 'open',
+        targetBranch: 'old_base',
+        bodyStruct: partial<PrBodyStruct>({
+          debugData: partial<PrDebugData>({ targetBranch: 'old_base' }),
+        }),
+      });
+      getUpdated.getUpdatedPackageFiles.mockResolvedValue(
+        partial<PackageFilesResult>({
+          updatedPackageFiles: [updatedPackageFile],
+        }),
+      );
+      npmPostExtract.getAdditionalFiles.mockResolvedValue({
+        artifactErrors: [partial<ArtifactError>()],
+        updatedArtifacts: [partial<FileChange>()],
+      });
+      scm.branchExists.mockResolvedValue(true);
+      commit.commitFilesToBranch.mockResolvedValueOnce(null);
+      platform.getBranchPr.mockResolvedValue(pr);
+      await branchWorker.processBranch({
+        ...config,
+        baseBranch: 'old_base',
+        reuseExistingBranch: true,
+        cacheFingerprintMatch: 'no-fingerprint',
+      });
+      expect(logger.debug).toHaveBeenCalledWith(
+        'Existing branch needs updating. Restarting processBranch() with a clean branch',
+      );
+      expect(commit.commitFilesToBranch).toHaveBeenCalled();
+      expect(prWorker.ensurePr).toHaveBeenCalledTimes(1);
+    });
+
+    // for coverage
+    it('rebases branch onto new basebranch if no fingerprint found - 2', async () => {
+      const pr = partial<Pr>({
+        state: 'open',
+        targetBranch: 'old_base',
+        bodyStruct: partial<PrBodyStruct>({
+          debugData: partial<PrDebugData>({ targetBranch: 'old_base' }),
+        }),
+      });
+      getUpdated.getUpdatedPackageFiles.mockResolvedValue(
+        partial<PackageFilesResult>({
+          updatedPackageFiles: [],
+        }),
+      );
+      npmPostExtract.getAdditionalFiles.mockResolvedValue({
+        artifactErrors: [partial<ArtifactError>()],
+        updatedArtifacts: [partial<FileChange>()],
+      });
+      scm.branchExists.mockResolvedValue(true);
+      commit.commitFilesToBranch.mockResolvedValueOnce(null);
+      platform.getBranchPr.mockResolvedValue(pr);
+      await branchWorker.processBranch({
+        ...config,
+        baseBranch: 'old_base',
+        reuseExistingBranch: true,
+        updatedArtifacts: [{ type: 'deletion', path: 'dummy' }],
+        cacheFingerprintMatch: 'no-fingerprint',
+      });
+      expect(logger.debug).toHaveBeenCalledWith(
+        'Existing branch needs updating. Restarting processBranch() with a clean branch',
+      );
+      expect(commit.commitFilesToBranch).toHaveBeenCalled();
+      expect(prWorker.ensurePr).toHaveBeenCalledTimes(1);
+    });
+
     it('swallows pr errors', async () => {
       getUpdated.getUpdatedPackageFiles.mockResolvedValueOnce(
         partial<PackageFilesResult>({

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

@@ -117,6 +117,7 @@ export interface ProcessBranchResult {
 
 export async function processBranch(
   branchConfig: BranchConfig,
+  forceRebase = false,
 ): Promise<ProcessBranchResult> {
   let commitSha: string | null = null;
   let config: BranchConfig = { ...branchConfig };
@@ -437,7 +438,10 @@ export async function processBranch(
       !!config.rebaseRequested;
     const userApproveAllPendingPR = !!config.dependencyDashboardAllPending;
     const userOpenAllRateLimtedPR = !!config.dependencyDashboardAllRateLimited;
-    if (userRebaseRequested) {
+    if (forceRebase) {
+      logger.debug('Force rebase because branch needs updating');
+      config.reuseExistingBranch = false;
+    } else if (userRebaseRequested) {
       logger.debug('User has requested rebase');
       config.reuseExistingBranch = false;
     } else if (dependencyDashboardCheck === 'global-config') {
@@ -501,6 +505,12 @@ export async function processBranch(
         logger.debug(
           `Updated ${config.updatedPackageFiles.length} package files`,
         );
+        if (config.reuseExistingBranch && !forceRebase) {
+          logger.debug(
+            'Existing branch needs updating. Restarting processBranch() with a clean branch',
+          );
+          return processBranch(branchConfig, true);
+        }
       } else {
         logger.debug('No package files need updating');
       }
@@ -523,6 +533,12 @@ export async function processBranch(
           },
           `Updated ${config.updatedArtifacts.length} lock files`,
         );
+        if (config.reuseExistingBranch && !forceRebase) {
+          logger.debug(
+            'Existing branch needs updating. Restarting processBranch() with a clean branch',
+          );
+          return processBranch(branchConfig, true);
+        }
       } else {
         logger.debug('No updated lock files in branch');
       }