From 0ae0c774e9e4640af388cd5b160d322998b4ef39 Mon Sep 17 00:00:00 2001
From: Bogdan Nechyporenko <bnechyporenko@bol.com>
Date: Mon, 17 Mar 2025 22:20:05 +0100
Subject: [PATCH] Made "publish:github:pull-request" action idempotent

Signed-off-by: Bogdan Nechyporenko <bnechyporenko@bol.com>
---
 .changeset/tough-clouds-live.md               |  5 ++
 .../package.json                              |  1 +
 .../src/actions/githubPullRequest.ts          | 64 ++++++++++++++-----
 yarn.lock                                     |  1 +
 4 files changed, 54 insertions(+), 17 deletions(-)
 create mode 100644 .changeset/tough-clouds-live.md

diff --git a/.changeset/tough-clouds-live.md b/.changeset/tough-clouds-live.md
new file mode 100644
index 0000000000..ff5638a7ef
--- /dev/null
+++ b/.changeset/tough-clouds-live.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-scaffolder-backend-module-github': patch
+---
+
+Made "publish:github:pull-request" action idempotent
diff --git a/plugins/scaffolder-backend-module-github/package.json b/plugins/scaffolder-backend-module-github/package.json
index 9ca633e659..824b6bcfbe 100644
--- a/plugins/scaffolder-backend-module-github/package.json
+++ b/plugins/scaffolder-backend-module-github/package.json
@@ -49,6 +49,7 @@
     "@backstage/errors": "workspace:^",
     "@backstage/integration": "workspace:^",
     "@backstage/plugin-scaffolder-node": "workspace:^",
+    "@backstage/types": "workspace:^",
     "@octokit/webhooks": "^10.9.2",
     "libsodium-wrappers": "^0.7.11",
     "octokit": "^3.0.0",
diff --git a/plugins/scaffolder-backend-module-github/src/actions/githubPullRequest.ts b/plugins/scaffolder-backend-module-github/src/actions/githubPullRequest.ts
index 5922c4e149..c0ff0fb3d4 100644
--- a/plugins/scaffolder-backend-module-github/src/actions/githubPullRequest.ts
+++ b/plugins/scaffolder-backend-module-github/src/actions/githubPullRequest.ts
@@ -35,6 +35,7 @@ import {
   resolveSafeChildPath,
 } from '@backstage/backend-plugin-api';
 import { Config } from '@backstage/config';
+import { JsonValue } from '@backstage/types';
 
 export type Encoding = 'utf-8' | 'base64';
 
@@ -425,18 +426,33 @@ export const createPublishGithubPullRequestAction = (
         if (targetBranchName) {
           createOptions.base = targetBranchName;
         }
-        const response = await client.createPullRequest(createOptions);
 
-        if (createWhenEmpty === false && !response) {
+        const pr = await ctx.checkpoint({
+          key: `create.pr.${owner}.${repo}.${branchName}`,
+          fn: async () => {
+            const response = await client.createPullRequest(createOptions);
+            if (!response) {
+              return null;
+            }
+
+            return {
+              base: response?.data.base,
+              html_url: response?.data.html_url,
+              number: response?.data.number,
+            };
+          },
+        });
+
+        if (createWhenEmpty === false && !pr) {
           ctx.logger.info('No changes to commit, pull request was not created');
           return;
         }
 
-        if (!response) {
+        if (!pr) {
           throw new GithubResponseError('null response from Github');
         }
 
-        const pullRequestNumber = response.data.number;
+        const pullRequestNumber = pr.number;
         if (reviewers || teamReviewers) {
           const pullRequest = { owner, repo, number: pullRequestNumber };
           await requestReviewersOnPullRequest(
@@ -445,12 +461,13 @@ export const createPublishGithubPullRequestAction = (
             teamReviewers,
             client,
             ctx.logger,
+            ctx.checkpoint,
           );
         }
 
-        const targetBranch = response.data.base.ref;
+        const targetBranch = pr.base.ref;
         ctx.output('targetBranchName', targetBranch);
-        ctx.output('remoteUrl', response.data.html_url);
+        ctx.output('remoteUrl', pr.html_url);
         ctx.output('pullRequestNumber', pullRequestNumber);
       } catch (e) {
         throw new GithubResponseError('Pull request creation failed', e);
@@ -464,20 +481,33 @@ export const createPublishGithubPullRequestAction = (
     teamReviewers: string[] | undefined,
     client: Octokit,
     logger: LoggerService,
+    checkpoint: <T extends JsonValue | void>(opts: {
+      key: string;
+      fn: () => Promise<T> | T;
+    }) => Promise<T>,
   ) {
     try {
-      const result = await client.rest.pulls.requestReviewers({
-        owner: pr.owner,
-        repo: pr.repo,
-        pull_number: pr.number,
-        reviewers,
-        team_reviewers: teamReviewers ? [...new Set(teamReviewers)] : undefined,
+      await checkpoint({
+        key: `request.reviewers.${pr.owner}.${pr.repo}.${pr.number}`,
+        fn: async () => {
+          const result = await client.rest.pulls.requestReviewers({
+            owner: pr.owner,
+            repo: pr.repo,
+            pull_number: pr.number,
+            reviewers,
+            team_reviewers: teamReviewers
+              ? [...new Set(teamReviewers)]
+              : undefined,
+          });
+
+          const addedUsers = result.data.requested_reviewers?.join(', ') ?? '';
+          const addedTeams = result.data.requested_teams?.join(', ') ?? '';
+
+          logger.info(
+            `Added users [${addedUsers}] and teams [${addedTeams}] as reviewers to Pull request ${pr.number}`,
+          );
+        },
       });
-      const addedUsers = result.data.requested_reviewers?.join(', ') ?? '';
-      const addedTeams = result.data.requested_teams?.join(', ') ?? '';
-      logger.info(
-        `Added users [${addedUsers}] and teams [${addedTeams}] as reviewers to Pull request ${pr.number}`,
-      );
     } catch (e) {
       logger.error(
         `Failure when adding reviewers to Pull request ${pr.number}`,
diff --git a/yarn.lock b/yarn.lock
index a6b0a736a0..ccdf8ec391 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -7623,6 +7623,7 @@ __metadata:
     "@backstage/integration": "workspace:^"
     "@backstage/plugin-scaffolder-node": "workspace:^"
     "@backstage/plugin-scaffolder-node-test-utils": "workspace:^"
+    "@backstage/types": "workspace:^"
     "@octokit/webhooks": ^10.9.2
     "@types/libsodium-wrappers": ^0.7.10
     fs-extra: ^11.2.0