BCR PR reviewer: properly deal with user renames (bazelbuild#2629)

We're currently querying GitHub with the maintainer's username to see
whether it matches the user ID. This doesn't work when the user has been
renamed. Instead, we can use the user ID to query for the up-to-date
username, and post a comment to the PR in case of a mismatch.
Effectively, this treats the user ID as the source of truth, which is
more stable and secure anyway.

Tested at Wyverald/bazel-central-registry#1

Author: Wyverald

actions/bcr-pr-reviewer/index.js

@@ -82,9 +82,10 @@ async function fetchAllModulesWithMetadataChange(octokit, owner, repo, prNumber)
   return await _processAllPrFiles(octokit, owner, repo, prNumber, fileProcessor);
 }
 
-async function generateMaintainersMap(octokit, owner, repo, modifiedModules, toNotifyOnly) {
+async function generateMaintainersMap(octokit, owner, repo, modifiedModules, toNotifyOnly, prNumber) {
   const maintainersMap = new Map(); // Map: maintainer GitHub username (lowercase) -> Set of module they maintain
   const modulesWithoutGithubMaintainers = new Set(); // Set of module names without module maintainers
+  const userIdToName = new Map(); // Map: github_user_id -> username; serves as a cache
   for (const moduleName of modifiedModules) {
     console.log(`Fetching metadata for module: ${moduleName}`);
     try {
@@ -99,28 +100,37 @@ async function generateMaintainersMap(octokit, owner, repo, modifiedModules, toN
       let hasGithubMaintainer = false;
       for (const maintainer of metadata.maintainers) {
         // Only add maintainers with a github handle set. When `toNotifyOnly`, also exclude those who have set "do_not_notify"
-        if (maintainer.github && !(toNotifyOnly && maintainer["do_not_notify"])) {
-          hasGithubMaintainer = true;
-          if (!maintainersMap.has(maintainer.github.toLowerCase())) {
-            try {
-              // Verify maintainer.github matches maintainer.github_user_id via GitHub API
-              const { data: user } = await octokit.rest.users.getByUsername({
-                username: maintainer.github,
-              });
-
-              if (!user || user.id !== maintainer.github_user_id) {
-                console.error(`Maintainer ${maintainer.github} does not match the user ID ${maintainer.github_user_id} or user not found`);
-                setFailed(`Maintainer ${maintainer.github} does not match the user ID ${maintainer.github_user_id} or user not found`);
-                return;
-              }
-              maintainersMap.set(maintainer.github.toLowerCase(), new Set());
-            } catch (error) {
-              console.error(`Failed to fetch user ID for GitHub username ${maintainer.github}: ${error.message}`);
-              setFailed(`Failed to fetch user ID for GitHub username ${maintainer.github}: ${error.message}`);
-              return;
-            }
+        if (!maintainer.github || (toNotifyOnly && maintainer["do_not_notify"])) {
+          continue;
+        }
+
+        hasGithubMaintainer = true;
+
+        if (!userIdToName.has(maintainer.github_user_id)) {
+          try {
+            const { data: user } = await octokit.request('GET /user/{account_id}', {
+              account_id: maintainer.github_user_id,
+            });
+
+            userIdToName.set(maintainer.github_user_id, user.login);
+            maintainersMap.set(user.login.toLowerCase(), new Set());
+          } catch (error) {
+            console.error(`Error fetching maintainer with GitHub ID ${maintainer.github_user_id}: ${error}`);
+            setFailed(`Error fetching maintainer with GitHub ID ${maintainer.github_user_id}: ${error}`);
+            return;
           }
-          maintainersMap.get(maintainer.github.toLowerCase()).add(moduleName);
+        }
+
+        const actualName = userIdToName.get(maintainer.github_user_id);
+        maintainersMap.get(actualName.toLowerCase()).add(moduleName);
+
+        // Detect if there's a mismatch between the github username in metadata.json and what GitHub reports
+        if (actualName.toLowerCase() !== maintainer.github.toLowerCase() && prNumber) {
+          console.log(`Detected GitHub username mismatch for user ID ${maintainer.github_user_id}: metadata.json has '${maintainer.github}', but GitHub has '${actualName}'.`);
+          const commentBody = `⚠️ **GitHub Username Mismatch Detected**\n\n` +
+            `The BCR registry entry for module **${moduleName}** contains an outdated GitHub username (\`@${maintainer.github}\`) that does not match their current active GitHub username (\`@${actualName}\`).\n\n` +
+            `Please update the \`metadata.json\` file of **${moduleName}** to use the up-to-date username \`"${actualName}"\` to ensure proper review routing and notifications.`;
+          await postComment(octokit, owner, repo, prNumber, commentBody);
         }
       }
 
@@ -447,7 +457,7 @@ async function reviewPR(octokit, owner, repo, prNumber) {
   }
 
   // Figure out maintainers for each modified module
-  const [maintainersMap, _] = await generateMaintainersMap(octokit, owner, repo, modifiedModules, /* toNotifyOnly= */ false);
+  const [maintainersMap, _] = await generateMaintainersMap(octokit, owner, repo, modifiedModules, /* toNotifyOnly= */ false, prNumber);
   console.log('Maintainers Map:');
   for (const [maintainer, maintainedModules] of maintainersMap.entries()) {
     console.log(`- Maintainer: ${maintainer}, Modules: ${Array.from(maintainedModules).join(', ')}`);
@@ -611,7 +621,7 @@ async function runNotifier(octokit) {
   console.log(`Modified modules: ${Array.from(modifiedModules).join(', ')}`);
 
   // Figure out maintainers for each modified module
-  const [ maintainersMap, modulesWithoutGithubMaintainers ] = await generateMaintainersMap(octokit, owner, repo, modifiedModules, /* toNotifyOnly= */ true);
+  const [maintainersMap, modulesWithoutGithubMaintainers] = await generateMaintainersMap(octokit, owner, repo, modifiedModules, /* toNotifyOnly= */ true, prNumber);
 
   // Notify maintainers for modules with module maintainers
   await notifyMaintainers(octokit, owner, repo, prNumber, maintainersMap);