gh-prs-merge: merge stacked PRs through the asynchronous merge endpoint (0.45.2)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@profullstack/cli-tools",
-  "version": "0.45.1",
+  "version": "0.45.2",
   "private": true,
   "description": "Local command-line tools, in TypeScript, exposed on PATH.",
   "type": "module",

src/gh.ts

@@ -124,6 +124,52 @@ export function parseChecks(raw: unknown, where = 'gh pr checks'): Check[] {
   });
 }
 
+/**
+ * The refusal GitHub returns from the GraphQL merge mutation for a pull
+ * request that belongs to a stack. Matched as a substring because the rest of
+ * the sentence carries a docs URL that is not ours to depend on.
+ */
+export const STACK_REFUSAL = 'asynchronous merge REST API';
+
+/** `https://github.com/owner/repo/pull/7` → `{ slug: 'owner/repo', number: 7 }`. */
+export function parsePullRequestUrl(
+  url: string,
+): { slug: string; number: string } | undefined {
+  const match = /github\.com\/([^/]+\/[^/]+)\/pull\/(\d+)/.exec(url);
+  return match ? { slug: match[1]!, number: match[2]! } : undefined;
+}
+
+export interface MergeAsyncState {
+  status?: string | undefined;
+  uuid?: string | undefined;
+  message?: string | undefined;
+}
+
+/**
+ * Read one asynchronous-merge reply. Unparseable output is not an error here:
+ * the caller treats a missing uuid as "stop polling" and reports that the
+ * merge never settled, which is truer than inventing a status.
+ */
+export function parseMergeAsync(stdout: string): MergeAsyncState | undefined {
+  let raw: unknown;
+  try {
+    raw = JSON.parse(stdout);
+  } catch {
+    return undefined;
+  }
+
+  if (typeof raw !== 'object' || raw === null) return undefined;
+
+  const record = raw as Record<string, unknown>;
+  const details = (record.details ?? {}) as Record<string, unknown>;
+
+  return {
+    status: typeof record.status === 'string' ? record.status : undefined,
+    uuid: typeof details.uuid === 'string' ? details.uuid : undefined,
+    message: typeof details.message === 'string' ? details.message : undefined,
+  };
+}
+
 export interface GhOptions {
   /** Swap in a fake for tests. */
   exec?: typeof run;
@@ -291,8 +337,89 @@ export class Gh {
    * lands on a commit nothing verified.
    *
    * Deliberately no `--admin`. Branch protections stay enforced.
+   *
+   * `gh pr merge` calls the GraphQL mergePullRequest mutation, and GitHub
+   * refuses that mutation outright for a PR that belongs to a stack, naming
+   * the asynchronous merge REST endpoint instead. Nothing is wrong with such
+   * a PR — it reports MERGEABLE and CLEAN — so there is no repair to attempt
+   * and no honest way to call it a refusal. Fall back to that endpoint.
    */
-  async squashMerge(url: string, headSha: string): Promise<RunResult> {
-    return this.call(['pr', 'merge', url, '--squash', '--match-head-commit', headSha]);
+  async squashMerge(
+    url: string,
+    headSha: string,
+    { pollMs = 2_000, attempts = 30 }: { pollMs?: number; attempts?: number } = {},
+  ): Promise<RunResult> {
+    const direct = await this.call([
+      'pr',
+      'merge',
+      url,
+      '--squash',
+      '--match-head-commit',
+      headSha,
+    ]);
+
+    if (direct.code === 0) return direct;
+
+    // Keyed on the message rather than on the base branch: GitHub still calls
+    // a PR stacked after it has retargeted it onto the default branch.
+    if (!`${direct.stderr}${direct.stdout}`.includes(STACK_REFUSAL)) return direct;
+
+    return this.mergeAsync(url, headSha, { pollMs, attempts });
+  }
+
+  /**
+   * The asynchronous merge endpoint enqueues the squash and hands back a uuid
+   * to poll. The head stays pinned and no `--admin` is passed, so the PR is
+   * held to exactly the rules it would have been held to above.
+   */
+  private async mergeAsync(
+    url: string,
+    headSha: string,
+    { pollMs, attempts }: { pollMs: number; attempts: number },
+  ): Promise<RunResult> {
+    const target = parsePullRequestUrl(url);
+    if (!target) {
+      return { code: 1, stdout: '', stderr: `cannot read owner/repo from ${url}` };
+    }
+
+    const endpoint = `repos/${target.slug}/pulls/${target.number}/merge-async`;
+
+    let response = await this.call([
+      'api',
+      '--method',
+      'PUT',
+      endpoint,
+      '-f',
+      'merge_method=squash',
+      '-f',
+      `sha=${headSha}`,
+    ]);
+
+    for (let attempt = 0; attempt < attempts; attempt += 1) {
+      if (response.code !== 0) return response;
+
+      const state = parseMergeAsync(response.stdout);
+
+      // `enqueued` means a merge queue owns it from here, which is as merged
+      // as this tool can make it.
+      if (state?.status === 'merged' || state?.status === 'enqueued') {
+        return {
+          code: 0,
+          stdout: `Merged ${url} via the asynchronous merge API`,
+          stderr: '',
+        };
+      }
+
+      if (state?.status === 'failed') {
+        return { code: 1, stdout: '', stderr: state.message ?? 'async merge failed' };
+      }
+
+      if (!state?.uuid) break;
+
+      await sleep(pollMs);
+      response = await this.call(['api', `${endpoint}/${state.uuid}`]);
+    }
+
+    return { code: 1, stdout: '', stderr: `async merge never settled for ${url}` };
   }
 }

test/prs-merge.test.ts

@@ -1,5 +1,12 @@
 import { describe, expect, it } from 'vitest';
-import { Gh, parseChecks, parsePullRequest, GhError } from '../src/gh.ts';
+import {
+  Gh,
+  parseChecks,
+  parseMergeAsync,
+  parsePullRequest,
+  parsePullRequestUrl,
+  GhError,
+} from '../src/gh.ts';
 import type { RunResult } from '../src/exec.ts';
 import {
   defaults,
@@ -32,10 +39,15 @@ function stubGh(options: {
   steps: StubStep[];
   updateBranchFails?: boolean;
   mergeFails?: boolean;
+  /** Refuse `pr merge` the way GitHub refuses a PR that is part of a stack. */
+  stacked?: boolean;
+  /** How many polls the asynchronous merge takes before it reports merged. */
+  asyncPolls?: number;
 }) {
   const calls: string[] = [];
   let viewIndex = 0;
   let checkIndex = 0;
+  let asyncPolls = options.asyncPolls ?? 0;
 
   const step = (index: number): StubStep =>
     options.steps[Math.min(index, options.steps.length - 1)]!;
@@ -83,11 +95,29 @@ function stubGh(options: {
     }
 
     if (args[0] === 'pr' && args[1] === 'merge') {
+      if (options.stacked) {
+        return {
+          code: 1,
+          stdout: '',
+          stderr:
+            'GraphQL: This pull request is part of a stack and must be merged ' +
+            'using the asynchronous merge REST API. (mergePullRequest)',
+        };
+      }
       return options.mergeFails
         ? { code: 1, stdout: '', stderr: 'refused' }
         : ok('Merged');
     }
 
+    // The asynchronous merge endpoint: the PUT enqueues, each GET polls.
+    if (args[0] === 'api' && args.some((a) => a.includes('merge-async'))) {
+      if (asyncPolls > 0) {
+        asyncPolls -= 1;
+        return ok(JSON.stringify({ status: 'pending', details: { uuid: 'u-1' } }));
+      }
+      return ok(JSON.stringify({ status: 'merged', details: { sha: 'cafe' } }));
+    }
+
     if (args[0] === 'pr' && args[1] === 'ready') return ok('');
 
     return ok('');
@@ -282,6 +312,26 @@ describe('sweep', () => {
     expect(summary.merged).toBe(0);
   });
 
+  it('merges a stacked PR through the asynchronous merge endpoint', async () => {
+    const { gh, calls } = stubGh({ steps: [{}], stacked: true });
+    const { summary } = await runSweep(gh, baseOptions());
+
+    expect(summary.merged).toBe(1);
+    expect(summary.failed).toBe(0);
+    expect(calls.some((c) => c.includes('merge-async'))).toBe(true);
+  });
+
+  it('pins the head commit on the asynchronous merge too', async () => {
+    const { gh, calls } = stubGh({ steps: [{}], stacked: true });
+    await runSweep(gh, baseOptions());
+
+    const put = calls.find((c) => c.startsWith('api --method PUT'));
+    expect(put).toContain('sha=deadbeef');
+    expect(put).toContain('merge_method=squash');
+    // Still no admin override on this path.
+    expect(calls.some((c) => c.includes('--admin'))).toBe(false);
+  });
+
   it('marks a draft ready, then judges it normally', async () => {
     const { gh, calls } = stubGh({ steps: [{ isDraft: true }, { isDraft: false }] });
     const { summary } = await runSweep(gh, baseOptions());
@@ -320,3 +370,120 @@ describe('defaults', () => {
     expect(defaults.pollMs).toBe(20_000);
   });
 });
+
+describe('asynchronous merge', () => {
+  const PR = 'https://github.com/acme/repo/pull/7';
+
+  /** A `gh` that refuses the mutation, then answers the REST endpoint. */
+  function stubAsync(replies: string[], { refuse = true } = {}) {
+    const calls: string[] = [];
+    let index = 0;
+
+    const exec = async (_f: string, args: readonly string[]): Promise<RunResult> => {
+      calls.push(args.join(' '));
+
+      if (args[0] === 'pr' && args[1] === 'merge') {
+        return refuse
+          ? {
+              code: 1,
+              stdout: '',
+              stderr: 'must be merged using the asynchronous merge REST API. (mergePullRequest)',
+            }
+          : { code: 0, stdout: 'Merged', stderr: '' };
+      }
+
+      const reply = replies[Math.min(index, replies.length - 1)]!;
+      index += 1;
+      return { code: 0, stdout: reply, stderr: '' };
+    };
+
+    return { gh: new Gh({ exec }), calls };
+  }
+
+  it('polls the uuid until the merge settles', async () => {
+    const { gh, calls } = stubAsync([
+      JSON.stringify({ status: 'pending', details: { uuid: 'u-1' } }),
+      JSON.stringify({ status: 'pending', details: { uuid: 'u-1' } }),
+      JSON.stringify({ status: 'merged', details: { sha: 'cafe' } }),
+    ]);
+
+    const result = await gh.squashMerge(PR, 'deadbeef', { pollMs: 1 });
+
+    expect(result.code).toBe(0);
+    expect(calls.filter((c) => c.startsWith('api repos/acme/repo/pulls/7/merge-async/u-1')))
+      .toHaveLength(2);
+  });
+
+  it('treats enqueued as merged, because a merge queue owns it from there', async () => {
+    const { gh } = stubAsync([JSON.stringify({ status: 'enqueued', details: { uuid: 'u-1' } })]);
+    const result = await gh.squashMerge(PR, 'deadbeef', { pollMs: 1 });
+
+    expect(result.code).toBe(0);
+  });
+
+  it('reports a failed asynchronous merge with the reason GitHub gave', async () => {
+    const { gh } = stubAsync([
+      JSON.stringify({ status: 'failed', details: { message: 'head moved' } }),
+    ]);
+    const result = await gh.squashMerge(PR, 'deadbeef', { pollMs: 1 });
+
+    expect(result.code).toBe(1);
+    expect(result.stderr).toContain('head moved');
+  });
+
+  it('gives up rather than polling forever', async () => {
+    const { gh } = stubAsync([JSON.stringify({ status: 'pending', details: { uuid: 'u-1' } })]);
+    const result = await gh.squashMerge(PR, 'deadbeef', { pollMs: 1, attempts: 3 });
+
+    expect(result.code).toBe(1);
+    expect(result.stderr).toContain('never settled');
+  });
+
+  it('does not reach for the endpoint when the refusal is a different one', async () => {
+    const calls: string[] = [];
+    const gh = new Gh({
+      exec: async (_f, args) => {
+        calls.push(args.join(' '));
+        return { code: 1, stdout: '', stderr: 'Pull request is not mergeable' };
+      },
+    });
+
+    const result = await gh.squashMerge(PR, 'deadbeef', { pollMs: 1 });
+
+    expect(result.code).toBe(1);
+    expect(calls.some((c) => c.includes('merge-async'))).toBe(false);
+  });
+
+  it('never merges twice when the mutation already worked', async () => {
+    const { gh, calls } = stubAsync([], { refuse: false });
+    const result = await gh.squashMerge(PR, 'deadbeef', { pollMs: 1 });
+
+    expect(result.code).toBe(0);
+    expect(calls.some((c) => c.includes('merge-async'))).toBe(false);
+  });
+});
+
+describe('parsePullRequestUrl', () => {
+  it('reads owner, repo and number', () => {
+    expect(parsePullRequestUrl('https://github.com/acme/repo/pull/7')).toEqual({
+      slug: 'acme/repo',
+      number: '7',
+    });
+  });
+
+  it('returns nothing for something that is not a PR url', () => {
+    expect(parsePullRequestUrl('https://example.com/acme/repo')).toBeUndefined();
+  });
+});
+
+describe('parseMergeAsync', () => {
+  it('lifts status, uuid and message out of the reply', () => {
+    expect(
+      parseMergeAsync(JSON.stringify({ status: 'failed', details: { message: 'no' } })),
+    ).toEqual({ status: 'failed', uuid: undefined, message: 'no' });
+  });
+
+  it('returns nothing rather than inventing a status', () => {
+    expect(parseMergeAsync('not json')).toBeUndefined();
+  });
+});