add reviewers as assignees on PRs

Signed-off-by: Siddhartha Ganguly <gangulysiddhartha22@gmail.com>

Author: gangulysiddhartha22-cmyk

.github/scripts/bot-pr-add-reviewers-as-assignees.js

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+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * @fileoverview
+ * Automatically adds requested individual reviewers as assignees on Pull Requests.
+ *
+ * This is part of the generic "on-review" infrastructure.
+ * Team reviewers are intentionally ignored (only individual users are assigned).
+ * Caps the number of assignees at MAX_ASSIGNEES (default: 2).
+ */
+
+const { createLogger, MAX_ASSIGNEES, BOT_NAME_ASSIGNEES } = require('./helpers/index.js');
+
+const logger = createLogger(BOT_NAME_ASSIGNEES);
+
+/**
+ * Resolves the PR number from context (pull_request_target or workflow_dispatch).
+ *
+ * @param {Object} context - GitHub Actions context object
+ * @returns {number|null} Valid PR number or null if invalid/missing
+ */
+function resolvePrNumber(context) {
+  if (context.eventName === 'workflow_dispatch') {
+    const manual = Number(context.payload.inputs?.pr_number);
+    if (!Number.isInteger(manual) || manual <= 0) {
+      logger.warn('Invalid PR number supplied. Skipping.');
+      return null;
+    }
+    return manual;
+  }
+
+  const prNumber = context.payload.pull_request?.number;
+  if (!Number.isInteger(prNumber) || prNumber <= 0) {
+    logger.warn('No PR number found. Skipping.');
+    return null;
+  }
+  return prNumber;
+}
+
+/**
+ * Extracts unique users to assign from requested reviewers.
+ *
+ * @param {Array<Object>} requestedReviewers - List of requested reviewers from PR
+ * @param {Set<string>} currentAssignees - Set of current assignee logins
+ * @returns {Set<string>} Set of logins that should be assigned
+ */
+function getUsersToAssign(requestedReviewers, currentAssignees) {
+  const usersToAssign = new Set();
+
+  for (const reviewer of requestedReviewers) {
+    if (reviewer?.login && !currentAssignees.has(reviewer.login)) {
+      usersToAssign.add(reviewer.login);
+    }
+  }
+  return usersToAssign;
+}
+
+/**
+ * Logs a warning if some reviewers were dropped due to the assignee cap.
+ *
+ * @param {Set<string>} usersToAssign
+ */
+function logAssigneeCapWarning(usersToAssign) {
+  if (usersToAssign.size > MAX_ASSIGNEES) {
+    const dropped = Array.from(usersToAssign).slice(MAX_ASSIGNEES);
+    logger.warn(`Assignee cap (${MAX_ASSIGNEES}) reached. Dropping: ${dropped.join(', ')}`);
+  }
+}
+
+/**
+ * Main handler that adds requested reviewers as assignees on a PR.
+ *
+ * Triggered by:
+ *   - `pull_request_target: review_requested`
+ *   - `workflow_dispatch` (for manual testing)
+ *
+ * Behavior:
+ *   - Only processes individual reviewers (`requested_reviewers`)
+ *   - Ignores team reviewers (`requested_teams`)
+ *   - Skips users who are already assignees
+ *   - Caps at `MAX_ASSIGNEES` (default: 2)
+ *   - Logs a warning when reviewers are dropped due to the cap
+ *
+ * @param {Object} params
+ * @param {Object} params.github - GitHub Octokit client instance
+ * @param {Object} params.context - GitHub Actions context object
+ * @returns {Promise<void>}
+ */
+module.exports = async ({ github, context }) => {
+  try {
+    const prNumber = resolvePrNumber(context);
+    if (!prNumber) return;
+
+    const owner = context.repo.owner;
+    const repo = context.repo.repo;
+
+    logger.log(`Processing PR #${prNumber}`);
+
+    const payloadPr = context.payload.pull_request;
+    const pr = (payloadPr && Number.isInteger(payloadPr.number))
+      ? payloadPr
+      : (await github.rest.pulls.get({
+          owner,
+          repo,
+          pull_number: prNumber
+        })).data;
+
+    const requestedReviewers = pr.requested_reviewers || [];
+    const requestedTeams = pr.requested_teams || [];
+    const currentAssignees = new Set((pr.assignees || []).map(a => a.login));
+
+    if (requestedTeams.length > 0) {
+      logger.info(`${requestedTeams.length} team reviewer(s) detected but ignored (only individual users are assigned)`);
+    }
+    const usersToAssign = getUsersToAssign(requestedReviewers, currentAssignees);
+    const assigneesList = Array.from(usersToAssign).slice(0, MAX_ASSIGNEES);
+
+    if (assigneesList.length === 0) {
+      logger.log('No new users to assign. Done.');
+      return;
+    }
+
+    logger.log(`Will assign: ${assigneesList.join(', ')}`);
+    logAssigneeCapWarning(usersToAssign);
+
+    await github.rest.issues.addAssignees({
+      owner,
+      repo,
+      issue_number: prNumber,
+      assignees: assigneesList
+    });
+
+    logger.log(`✅ Successfully added ${assigneesList.length} reviewer(s) as assignee(s)`);
+
+  } catch (error) {
+    logger.error('Failed:', error.message);
+    if (error.status === 403) {
+      logger.warn('Insufficient permissions - skipping');
+      return;
+    }
+    throw error;
+  }
+};

.github/scripts/helpers/constants.js

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+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * Shared constants used by review-related GitHub Actions bots.
+ *
+ * @module constants
+ */
+
+module.exports = {
+  MAX_ASSIGNEES: 2,
+  BOT_NAME_ASSIGNEES: 'reviewers-assignee',
+};

.github/scripts/helpers/index.js

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+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * @fileoverview
+ * Central export file for all helper modules used by review bots.
+ */
+
+const { createLogger } = require('./logger.js');
+const constants = require('./constants.js');
+
+module.exports = {
+  createLogger,
+  MAX_ASSIGNEES: constants.MAX_ASSIGNEES,
+  BOT_NAME_ASSIGNEES: constants.BOT_NAME_ASSIGNEES,
+};

.github/scripts/helpers/logger.js

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+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * @fileoverview
+ * Simple logger utility for GitHub Actions bots with consistent
+ * prefixes and levels.
+ */
+
+/**
+ * Creates a logger instance for a specific bot.
+ *
+ * @param {string} botName - Name of the bot (e.g. 'reviewers-assignee')
+ * @returns {Object} Logger with info, warn, error methods
+ */
+function createLogger(botName) {
+  const prefix = `[${botName}]`;
+  return {
+    log:   (...args) => console.log(prefix, ...args),
+    info:  (...args) => console.info(prefix, ...args),
+    warn:  (...args) => console.warn(prefix, ...args),
+    error: (...args) => console.error(prefix, ...args),
+  };
+}
+
+module.exports = { createLogger };