feat: post processors can specify new PR title and body

packages/owl-bot/cloud-build/update-pr.yaml

@@ -59,6 +59,7 @@ steps:
     dir: '${_PR_REPOSITORY}'
     env:
       - 'DEFAULT_BRANCH=$_DEFAULT_BRANCH'
+      - 'NEW_PULL_REQUEST_TEXT_PATH=/workspace/new_pull_request_text.txt'
 
   # Install credentials *after* running the container.
   - name: 'bash'
@@ -91,6 +92,9 @@ steps:
       - ${_PR}
       - --github-token
       - ${_GITHUB_TOKEN}
+      - --new-pull-request-text-path
+      - /workspace/new_pull_request_text.txt
+
     dir: ${_PR_REPOSITORY}
     env:
       - 'HOME=/workspace'

packages/owl-bot/src/bin/commands/commit-post-processor-update.ts

@@ -31,12 +31,15 @@ import * as proc from 'child_process';
 import path = require('path');
 import {githubRepoFromOwnerSlashName} from '../../github-repo';
 import {hasGitChanges} from '../../git-utils';
+import * as fs from 'fs';
+import {resplit, WithRegenerateCheckbox} from '../../create-pr';
 
 interface Args {
   'dest-repo': string;
   pr: number;
   'github-token': string;
   'repo-path': string;
+  'new-pull-request-text-path': string;
 }
 
 export const commitPostProcessorUpdateCommand: yargs.CommandModule<{}, Args> = {
@@ -64,6 +67,12 @@ export const commitPostProcessorUpdateCommand: yargs.CommandModule<{}, Args> = {
         type: 'string',
         demand: true,
       })
+      .option('new-pull-request-text-path', {
+        describe:
+          'Path to a text file containing the new pull request title and body.',
+        type: 'string',
+        default: '',
+      })
       .option('repo-path', {
         describe: 'Local path to the repository',
         type: 'string',
@@ -95,11 +104,12 @@ export async function commitPostProcessorUpdate(args: Args): Promise<void> {
   // Check if the ignore label has been added during the post-processing.
   // If so, do not push changes.
   console.log(`Retrieving PR info for ${repo}`);
-  const {data: prData} = await octokit.pulls.get({
+  const prOwnerRepoPullNumber = {
     owner: repo.owner,
     repo: repo.repo,
     pull_number: args.pr,
-  });
+  };
+  const {data: prData} = await octokit.pulls.get(prOwnerRepoPullNumber);
   console.log(`Retrieved PR info for ${repo}`);
 
   if (prData.labels.find(label => label.name === OWL_BOT_IGNORE)) {
@@ -138,6 +148,14 @@ export async function commitPostProcessorUpdate(args: Args): Promise<void> {
   cmd('git pull --no-verify', {cwd: repoDir});
   // Push changes back to origin.
   cmd('git push --no-verify', {cwd: repoDir});
+
+  // Update the PR title and body if new ones were provided.
+  const text_path = args['new-pull-request-text-path'];
+  if (text_path && fs.existsSync(text_path)) {
+    const text = fs.readFileSync(text_path).toString();
+    const prContent = resplit(text, WithRegenerateCheckbox.No);
+    await octokit.pulls.update({...prOwnerRepoPullNumber, ...prContent});
+  }
 }
 
 export function commitOwlbotUpdate(repoDir: string) {

packages/owl-bot/test/commit-post-processor-update.ts

@@ -22,6 +22,7 @@ import {copyTagFrom} from '../src/copy-code';
 import sinon from 'sinon';
 import nock from 'nock';
 import {OWL_BOT_IGNORE, OWLBOT_RUN_LABEL} from '../src/labels';
+import * as fs from 'fs';
 
 export function makeOrigin(logger = console): string {
   const cmd = newCmd(logger);
@@ -104,6 +105,7 @@ describe('commitPostProcessorUpdate', () => {
       pr,
       'github-token': gitHubToken,
       'repo-path': repoPath,
+      'new-pull-request-text-path': '',
     };
   }
 
@@ -177,21 +179,48 @@ describe('commitPostProcessorUpdate', () => {
     assert.match(log, /Updates from OwlBot/);
   });
 
-  it('adds commit when .OwlBot.yaml contains no flag', async () => {
+  function makeRepoWithPendingCommit(): {origin: string; clone: string} {
     const origin = makeOrigin();
     const clone = cloneRepo(origin);
     makeDirTree(clone, [`${yamlPath}:deep-remove-regex:\n  - /pasta.txt`]);
     cmd(`git add ${yamlPath}`, {cwd: clone});
     const copyTag = copyTagFrom(yamlPath, 'abc123');
     cmd(`git commit -m "Copy-Tag: ${copyTag}"`, {cwd: clone});
     makeDirTree(clone, ['a.txt:The post processor ran.']);
+    return {origin, clone};
+  }
+
+  it('adds commit when .OwlBot.yaml contains no flag', async () => {
+    const {origin, clone} = makeRepoWithPendingCommit();
     await commitPostProcessorUpdate(prepareArgs(clone));
     const log = cmd('git log --format=%B main', {cwd: origin}).toString(
       'utf-8'
     );
     assert.match(log, /Updates from OwlBot/);
   });
 
+  it('updates pr title and body', async () => {
+    const {origin, clone} = makeRepoWithPendingCommit();
+    const args = prepareArgs(clone);
+    args['new-pull-request-text-path'] = tmp.fileSync().name;
+    fs.writeFileSync(
+      args['new-pull-request-text-path'],
+      'updated title\n\nUpdated body.'
+    );
+    // commitPostProcessorUpdate() should issue a PATCH request to update the PR.
+    nock('https://api.github.com')
+      .patch(`/repos/${destRepo}/pulls/${pr}`, {
+        title: 'updated title',
+        body: 'Updated body.',
+      })
+      .reply(204);
+    await commitPostProcessorUpdate(args);
+    const log = cmd('git log --format=%B main', {cwd: origin}).toString(
+      'utf-8'
+    );
+    assert.match(log, /Updates from OwlBot/);
+  });
+
   it('squashes commit when .OwlBot.yaml contains flag', async () => {
     const origin = makeOrigin();
     const clone = cloneRepo(origin);