feat(github): update pr baseBranch (#22663)

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

lib/modules/platform/github/index.spec.ts

@@ -2829,6 +2829,22 @@ describe('modules/platform/github/index', () => {
 
       await expect(github.updatePr(pr)).toResolve();
     });
+
+    it('should update target branch', async () => {
+      const pr: UpdatePrConfig = {
+        number: 1234,
+        prTitle: 'The New Title',
+        prBody: 'Hello world again',
+        state: 'closed',
+        targetBranch: 'new_base',
+      };
+      const scope = httpMock.scope(githubApiHost);
+      initRepoMock(scope, 'some/repo');
+      await github.initRepo({ repository: 'some/repo' });
+      scope.patch('/repos/some/repo/pulls/1234').reply(200, pr);
+
+      await expect(github.updatePr(pr)).toResolve();
+    });
   });
 
   describe('mergePr(prNo)', () => {

lib/modules/platform/github/index.ts

@@ -1602,6 +1602,7 @@ export async function updatePr({
   prTitle: title,
   prBody: rawBody,
   state,
+  targetBranch,
 }: UpdatePrConfig): Promise<void> {
   logger.debug(`updatePr(${prNo}, ${title}, body)`);
   const body = sanitize(rawBody);
@@ -1609,6 +1610,9 @@ export async function updatePr({
   if (body) {
     patchBody.body = body;
   }
+  if (targetBranch) {
+    patchBody.base = targetBranch;
+  }
   if (state) {
     patchBody.state = state;
   }

lib/modules/platform/types.ts

@@ -112,6 +112,7 @@ export interface UpdatePrConfig {
   prTitle: string;
   prBody?: string;
   state?: 'open' | 'closed';
+  targetBranch?: string;
 }
 export interface EnsureIssueConfig {
   title: string;

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

@@ -65,6 +65,7 @@ describe('workers/repository/update/pr/index', () => {
       title: prTitle,
       bodyStruct,
       state: 'open',
+      targetBranch: 'base',
     };
 
     const config: BranchConfig = {
@@ -304,6 +305,32 @@ describe('workers/repository/update/pr/index', () => {
         );
       });
 
+      it('updates PR target branch if base branch changed in config', async () => {
+        platform.getBranchPr.mockResolvedValueOnce(pr);
+
+        const res = await ensurePr({ ...config, baseBranch: 'new_base' }); // user changed base branch in config
+
+        expect(platform.updatePr).toHaveBeenCalled();
+        expect(platform.createPr).not.toHaveBeenCalled();
+        expect(prCache.setPrCache).toHaveBeenCalled();
+        expect(logger.logger.info).toHaveBeenCalledWith(
+          { pr: pr.number, prTitle },
+          `PR updated`
+        );
+        expect(logger.logger.debug).toHaveBeenCalledWith(
+          {
+            branchName: 'renovate-branch',
+            oldBaseBranch: 'base',
+            newBaseBranch: 'new_base',
+          },
+          'PR base branch has changed'
+        );
+        expect(res).toEqual({
+          type: 'with-pr',
+          pr: { ...pr, targetBranch: 'new_base' }, // updated target branch of pr
+        });
+      });
+
       it('ignores reviewable content ', async () => {
         // See: https://reviewable.io/
 
@@ -892,6 +919,7 @@ describe('workers/repository/update/pr/index', () => {
             title: prTitle,
             bodyStruct,
             state: 'open',
+            targetBranch: 'base',
           },
         });
         expect(logger.logger.debug).toHaveBeenCalledWith(

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

@@ -342,6 +342,7 @@ export async function ensurePr(
       const newPrTitle = stripEmojis(prTitle);
       const newPrBodyHash = hashBody(prBody);
       if (
+        existingPr?.targetBranch === config.baseBranch &&
         existingPrTitle === newPrTitle &&
         existingPrBodyHash === newPrBodyHash
       ) {
@@ -353,6 +354,16 @@ export async function ensurePr(
         return { type: 'with-pr', pr: existingPr };
       }
       // PR must need updating
+      if (existingPr?.targetBranch !== config.baseBranch) {
+        logger.debug(
+          {
+            branchName,
+            oldBaseBranch: existingPr?.targetBranch,
+            newBaseBranch: config.baseBranch,
+          },
+          'PR base branch has changed'
+        );
+      }
       if (existingPrTitle !== newPrTitle) {
         logger.debug(
           {
@@ -370,6 +381,7 @@ export async function ensurePr(
           'PR body changed'
         );
       }
+
       if (GlobalConfig.get('dryRun')) {
         logger.info(`DRY-RUN: Would update PR #${existingPr.number}`);
         return { type: 'with-pr', pr: existingPr };
@@ -379,6 +391,7 @@ export async function ensurePr(
           prTitle,
           prBody,
           platformOptions: getPlatformPrOptions(config),
+          targetBranch: config.baseBranch,
         });
         logger.info({ pr: existingPr.number, prTitle }, `PR updated`);
         setPrCache(branchName, prBodyFingerprint, true);
@@ -389,6 +402,7 @@ export async function ensurePr(
           ...existingPr,
           bodyStruct: getPrBodyStruct(prBody),
           title: prTitle,
+          targetBranch: config.baseBranch,
         },
       };
     }
@@ -412,7 +426,7 @@ export async function ensurePr(
         }
         pr = await platform.createPr({
           sourceBranch: branchName,
-          targetBranch: config.baseBranch ?? '',
+          targetBranch: config.baseBranch,
           prTitle,
           prBody,
           labels: prepareLabels(config),

lib/workers/repository/update/pr/pr-fingerprint.ts

@@ -24,6 +24,7 @@ export interface FilteredBranchUpgradeConfig {
 export interface PrBodyFingerprintConfig {
   // BranchConfig - filtered
   automerge?: boolean;
+  baseBranch?: string;
   automergeSchedule?: string[];
   hasReleaseNotes?: boolean;
   isPin?: boolean;
@@ -63,6 +64,7 @@ export function generatePrBodyFingerprintConfig(
   return {
     automerge: config.automerge,
     automergeSchedule: config.automergeSchedule,
+    baseBranch: config.baseBranch,
     filteredUpgrades,
     hasReleaseNotes: config.hasReleaseNotes,
     isPin: config.isPin,