feat(platform): re-attempt platform automerge on github and gitlab

docs/usage/configuration-options.md

@@ -3003,8 +3003,9 @@ If enabled Renovate will pin Docker images or GitHub Actions by means of their S
 
 If you have enabled `automerge` and set `automergeType=pr` in the Renovate config, then leaving `platformAutomerge` as `true` speeds up merging via the platform's native automerge functionality.
 
-Renovate tries platform-native automerge only when it initially creates the PR.
+On most platforms, Renovate tries platform-native automerge only when it initially creates the PR.
 Any PR that is being updated will be automerged with the Renovate-based automerge.
+On GitHub, Renovate re-enables the PR for automerge whenever it's rebased, so that merge conflicts encountered in the Merge Queue can be resolved.
 
 `platformAutomerge` will configure PRs to be merged after all (if any) branch policies have been met.
 This option is available for Azure, Gitea, GitHub and GitLab.

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

@@ -17,7 +17,12 @@ import * as _hostRules from '../../../util/host-rules';
 import { setBaseUrl } from '../../../util/http/github';
 import { toBase64 } from '../../../util/string';
 import { hashBody } from '../pr-body';
-import type { CreatePRConfig, RepoParams, UpdatePrConfig } from '../types';
+import type {
+  CreatePRConfig,
+  ReattemptPlatformAutomergeConfig,
+  RepoParams,
+  UpdatePrConfig,
+} from '../types';
 import * as branch from './branch';
 import type { ApiPageCache, GhRestPr } from './types';
 import * as github from '.';
@@ -3111,6 +3116,86 @@ describe('modules/platform/github/index', () => {
     });
   });
 
+  describe('reattemptPlatformAutomerge(prNo, platformOptions)', () => {
+    const getPrResp = {
+      number: 123,
+      node_id: 'abcd',
+      head: { repo: { full_name: 'some/repo' } },
+    };
+
+    const graphqlAutomergeResp = {
+      data: {
+        enablePullRequestAutoMerge: {
+          pullRequest: {
+            number: 123,
+          },
+        },
+      },
+    };
+
+    const pr: ReattemptPlatformAutomergeConfig = {
+      prNo: 123,
+      platformOptions: { usePlatformAutomerge: true },
+    };
+
+    const mockScope = async (repoOpts: any = {}): Promise<httpMock.Scope> => {
+      const scope = httpMock.scope(githubApiHost);
+      initRepoMock(scope, 'some/repo', repoOpts);
+      scope.get('/repos/some/repo/pulls/123').reply(200, getPrResp);
+      await github.initRepo({ repository: 'some/repo' });
+      return scope;
+    };
+
+    const graphqlGetRepo = {
+      method: 'POST',
+      url: 'https://api.github.com/graphql',
+      graphql: { query: { repository: {} } },
+    };
+
+    const restGetPr = {
+      method: 'GET',
+      url: 'https://api.github.com/repos/some/repo/pulls/123',
+    };
+
+    const graphqlAutomerge = {
+      method: 'POST',
+      url: 'https://api.github.com/graphql',
+      graphql: {
+        mutation: {
+          __vars: {
+            $pullRequestId: 'ID!',
+            $mergeMethod: 'PullRequestMergeMethod!',
+          },
+          enablePullRequestAutoMerge: {
+            __args: {
+              input: {
+                pullRequestId: '$pullRequestId',
+                mergeMethod: '$mergeMethod',
+              },
+            },
+          },
+        },
+        variables: {
+          pullRequestId: 'abcd',
+          mergeMethod: 'REBASE',
+        },
+      },
+    };
+
+    it('should set automatic merge', async () => {
+      const scope = await mockScope();
+      scope.post('/graphql').reply(200, graphqlAutomergeResp);
+
+      await expect(github.reattemptPlatformAutomerge(pr)).toResolve();
+
+      expect(httpMock.getTrace()).toMatchObject([
+        graphqlGetRepo,
+        restGetPr,
+        graphqlAutomerge,
+      ]);
+    });
+  });
+
   describe('mergePr(prNo)', () => {
     it('should merge the PR', async () => {
       const scope = httpMock.scope(githubApiHost);

lib/modules/platform/github/index.ts

@@ -56,6 +56,7 @@ import type {
   PlatformParams,
   PlatformPrOptions,
   PlatformResult,
+  ReattemptPlatformAutomergeConfig,
   RepoParams,
   RepoResult,
   UpdatePrConfig,
@@ -1731,6 +1732,25 @@ export async function updatePr({
   }
 }
 
+export async function reattemptPlatformAutomerge({
+  prNo,
+  platformOptions,
+}: ReattemptPlatformAutomergeConfig): Promise<void> {
+  try {
+    const result = (await getPr(prNo))!;
+    const { number, node_id } = result;
+
+    await tryPrAutomerge(number, node_id, platformOptions);
+
+    logger.debug(`PR platform automerge re-attempted...prNo: ${prNo}`);
+  } catch (err) /* istanbul ignore next */ {
+    if (err instanceof ExternalHostError) {
+      throw err;
+    }
+    logger.warn({ err }, 'Error re-attempting PR platform automerge');
+  }
+}
+
 export async function mergePr({
   branchName,
   id: prNo,

lib/modules/platform/types.ts

@@ -121,6 +121,10 @@ export interface UpdatePrConfig {
   state?: 'open' | 'closed';
   targetBranch?: string;
 }
+export interface ReattemptPlatformAutomergeConfig {
+  prNo: number;
+  platformOptions?: PlatformPrOptions;
+}
 export interface EnsureIssueConfig {
   title: string;
   reuseTitle?: string;
@@ -223,6 +227,9 @@ export interface Platform {
   getPr(number: number): Promise<Pr | null>;
   findPr(findPRConfig: FindPRConfig): Promise<Pr | null>;
   refreshPr?(number: number): Promise<void>;
+  reattemptPlatformAutomerge?(
+    prConfig: ReattemptPlatformAutomergeConfig,
+  ): Promise<void>;
   getBranchStatus(
     branchName: string,
     internalChecksAsSuccess: boolean,

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

@@ -108,6 +108,7 @@ describe('workers/repository/update/branch/index', () => {
     beforeEach(() => {
       scm.branchExists.mockResolvedValue(false);
       prWorker.ensurePr = jest.fn();
+      prWorker.getPlatformPrOptions = jest.fn();
       prAutomerge.checkAutoMerge = jest.fn();
       // TODO: incompatible types (#22198)
       config = {
@@ -133,6 +134,9 @@ describe('workers/repository/update/branch/index', () => {
           state: '',
         }),
       });
+      prWorker.getPlatformPrOptions.mockReturnValue({
+        usePlatformAutomerge: true,
+      });
       GlobalConfig.set(adminConfig);
       // TODO: fix types, jest is using wrong overload (#22198)
       sanitize.sanitize.mockImplementation((input) => input!);

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

@@ -36,7 +36,7 @@ import * as template from '../../../../util/template';
 import { isLimitReached } from '../../../global/limits';
 import type { BranchConfig, BranchResult, PrBlockedBy } from '../../../types';
 import { embedChangelogs } from '../../changelog';
-import { ensurePr } from '../pr';
+import { ensurePr, getPlatformPrOptions } from '../pr';
 import { checkAutoMerge } from '../pr/automerge';
 import { setArtifactErrorStatus } from './artifacts';
 import { tryBranchAutomerge } from './automerge';
@@ -570,9 +570,22 @@ export async function processBranch(
       await scm.checkoutBranch(config.baseBranch);
       updatesVerified = true;
     }
-    // istanbul ignore if
-    if (branchPr && platform.refreshPr) {
-      await platform.refreshPr(branchPr.number);
+
+    if (branchPr) {
+      const platformOptions = getPlatformPrOptions(config);
+      if (
+        platformOptions.usePlatformAutomerge &&
+        platform.reattemptPlatformAutomerge
+      ) {
+        await platform.reattemptPlatformAutomerge({
+          prNo: branchPr.number,
+          platformOptions,
+        });
+      }
+      // istanbul ignore if
+      if (platform.refreshPr) {
+        await platform.refreshPr(branchPr.number);
+      }
     }
     if (!commitSha && !branchExists) {
       return {