feat: issue-PR linking plugin to comment on issues (#226)

* Initial plan

* Implement issue-PR linking plugin to comment on issues when PRs reference them

Co-authored-by: nzakas <[email protected]>

* Address PR feedback: update regex keywords, remove unused parameter, switch to PR body processing

Co-authored-by: nzakas <[email protected]>

* Address PR feedback: improve regex with word boundaries and named groups, add JSDoc comments, use array for event listeners, add EOL, and enhance test coverage

Co-authored-by: lumirlumir <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: nzakas <[email protected]>
Co-authored-by: lumirlumir <[email protected]>

Author: 3 people

src/app.js

@@ -25,6 +25,7 @@ const plugins = require("./plugins");
 const enabledPlugins = new Set([
     "autoAssign",
     "commitMessage",
+    "issuePrLink",
     "needsInfo",
     "recurringIssues",
     "releaseMonitor",

src/plugins/index.js

@@ -15,6 +15,7 @@
 module.exports = {
     autoAssign: require("./auto-assign"),
     commitMessage: require("./commit-message"),
+    issuePrLink: require("./issue-pr-link"),
     needsInfo: require("./needs-info"),
     recurringIssues: require("./recurring-issues"),
     releaseMonitor: require("./release-monitor"),

src/plugins/issue-pr-link/index.js

@@ -0,0 +1,169 @@
+/**
+ * @fileoverview Comment on issues when PRs are created/edited to fix them
+ * @author ESLint GitHub Bot Contributors
+ */
+
+"use strict";
+
+//-----------------------------------------------------------------------------
+// Type Definitions
+//-----------------------------------------------------------------------------
+
+/** @typedef {import("probot").Context} ProbotContext */
+
+//-----------------------------------------------------------------------------
+// Helpers
+//-----------------------------------------------------------------------------
+
+/**
+ * Regex to find issue references in PR bodies
+ * Matches patterns like: "Fix #123", "Fixes #123", "Closes #123", "Resolves #123", etc.
+ */
+const ISSUE_REFERENCE_REGEX = /\b(?:fix|fixes|fixed|close|closes|closed|resolve|resolves|resolved)\b:?[ \t]+#(?<issueNumber>\d+)/giu;
+
+/**
+ * Maximum number of issues to comment on per PR to prevent abuse
+ */
+const MAX_ISSUES_PER_PR = 3;
+
+/**
+ * Extract issue numbers from PR body
+ * @param {string} body PR body
+ * @returns {number[]} Array of issue numbers
+ * @private
+ */
+function extractIssueNumbers(body) {
+    const matches = [];
+    let match;
+
+    // Reset regex lastIndex to ensure we start from the beginning
+    ISSUE_REFERENCE_REGEX.lastIndex = 0;
+
+    while ((match = ISSUE_REFERENCE_REGEX.exec(body)) !== null && matches.length < MAX_ISSUES_PER_PR) {
+        const issueNumber = parseInt(match.groups.issueNumber, 10);
+        if (!matches.includes(issueNumber)) {
+            matches.push(issueNumber);
+        }
+    }
+
+    return matches;
+}
+
+/**
+ * Create the comment message for the issue
+ * @param {string} prUrl URL of the pull request
+ * @param {string} prAuthor Author of the pull request
+ * @returns {string} comment message
+ * @private
+ */
+function createCommentMessage(prUrl, prAuthor) {
+    return `👋 Hi! This issue is being addressed in pull request ${prUrl}. Thanks, @${prAuthor}!
+
+[//]: # (issue-pr-link)`;
+}
+
+/**
+ * Check if an issue exists and is open
+ * @param {ProbotContext} context Probot context object
+ * @param {number} issueNumber Issue number to check
+ * @returns {Promise<boolean>} True if issue exists and is open
+ * @private
+ */
+async function isIssueOpenAndExists(context, issueNumber) {
+    try {
+        const { data: issue } = await context.octokit.issues.get(
+            context.repo({ issue_number: issueNumber })
+        );
+        return issue.state === "open";
+    } catch {
+        // Issue doesn't exist or we don't have access
+        return false;
+    }
+}
+
+/**
+ * Check if we already commented on this issue for this PR
+ * @param {ProbotContext} context Probot context object
+ * @param {number} issueNumber Issue number
+ * @param {number} prNumber PR number
+ * @returns {Promise<boolean>} True if we already commented
+ * @private
+ */
+async function hasExistingComment(context, issueNumber, prNumber) {
+    try {
+        const { data: comments } = await context.octokit.issues.listComments(
+            context.repo({ issue_number: issueNumber })
+        );
+
+        const botComments = comments.filter(comment => 
+            comment.user.type === "Bot" && 
+            comment.body.includes("[//]: # (issue-pr-link)") &&
+            comment.body.includes(`/pull/${prNumber}`)
+        );
+
+        return botComments.length > 0;
+    } catch {
+        // If we can't check comments, assume we haven't commented
+        return false;
+    }
+}
+
+/**
+ * Comment on issues referenced in the PR body
+ * @param {ProbotContext} context Probot context object
+ * @returns {Promise<void>}
+ * @private
+ */
+async function commentOnReferencedIssues(context) {
+    const { payload } = context;
+    const pr = payload.pull_request;
+    
+    if (!pr || !pr.body) {
+        return;
+    }
+
+    const issueNumbers = extractIssueNumbers(pr.body);
+    
+    if (issueNumbers.length === 0) {
+        return;
+    }
+
+    const prUrl = pr.html_url;
+    const prAuthor = pr.user.login;
+    const prNumber = pr.number;
+
+    // Comment on each referenced issue
+    for (const issueNumber of issueNumbers) {
+        try {
+            // Check if issue exists and is open
+            if (!(await isIssueOpenAndExists(context, issueNumber))) {
+                continue;
+            }
+
+            // Check if we already commented on this issue for this PR
+            if (await hasExistingComment(context, issueNumber, prNumber)) {
+                continue;
+            }
+
+            // Create the comment
+            await context.octokit.issues.createComment(
+                context.repo({
+                    issue_number: issueNumber,
+                    body: createCommentMessage(prUrl, prAuthor)
+                })
+            );
+        } catch (error) {
+            // Log error but continue with other issues
+            // eslint-disable-next-line no-console -- Logging errors is intentional
+            console.error(`Failed to comment on issue #${issueNumber}:`, error);
+        }
+    }
+}
+
+//-----------------------------------------------------------------------------
+// Robot
+//-----------------------------------------------------------------------------
+
+module.exports = robot => {
+    robot.on(["pull_request.opened", "pull_request.edited"], commentOnReferencedIssues);
+};