release-pr-coderabbit-gate.js

/**
 * Posts a single "@coderabbit review" comment on release PRs, embedding the
 * release review prompt. Designed to run with:
 * - permissions: contents: read, pull-requests: write
 *
 * Safety:
 * - Only runs for maintainer-authored PRs (MEMBER/OWNER)
 * - Dedupe via hidden marker comment
 */

const fs = require("fs");
const path = require("path");

const MARKER = "<!-- coderabbit-release-gate: v1 -->";


function loadPrompt() {
  const promptPath = path.join(
    process.env.GITHUB_WORKSPACE || ".", 
    ".github/coderabbit/release-pr-prompt.md"
  );
  try {
    const content = fs.readFileSync(promptPath, "utf8").trim();
    if (!content) {
      throw new Error("Release prompt file is empty");
    }
    return content;
  } catch (error) {
    throw new Error(`Failed to load release prompt from ${promptPath}: ${error.message}`);
  }
}

async function commentAlreadyExists({ github, owner, repo, issue_number }) {
  try {
      // Pull a bounded number of recent comments to avoid pagination complexity.
      const { data } = await github.rest.issues.listComments({
      owner,
      repo,
      issue_number,
      per_page: 100,
      });
        return data.some((c) => typeof c.body === "string" && c.body.includes(MARKER));
      }
  catch (error) {
      console.error(`Error checking for existing comments: ${error.message}`);
      return false; // Fail open: allow posting if check fails
      }
}


function buildBody({ prompt, baseRef, headRef, baseLooksLikeTag }) {
  // Keep it human-friendly but compact; instructions are collapsible.
  const lines = [
    "@coderabbitai review",
    "",
    MARKER,
    "",
    `This is a **release-gate** review request for diff **${baseRef} → ${headRef}**.`,
    "",
  ];
  if (!baseLooksLikeTag) {
    lines.push(
    "⚠️ Warning: The base ref does not look like a release tag. For a full release diff, set base to the previous tag (e.g., release-v0.1.10).",
    ""
    );
  }

  lines.push(
      "<details>",
      "<summary>CodeRabbit release review instructions</summary>",
      "",
      prompt,
      "",
      "</details>",
    );
  return lines.join("\n");

}

module.exports = async ({ github, context }) => {
  try {
    const owner = context.repo.owner;
    const repo = context.repo.repo;
    const pr = context.payload.pull_request;

    if (!pr) {
      console.log("No pull_request payload; exiting.");
      return;
    }

    // Safety: only maintainers
    const assoc = pr.author_association;
    if (!(assoc === "MEMBER" || assoc === "OWNER")) {
      console.log(`author_association=${assoc}; skipping.`);
      return;
    }

    const title = pr.title || "";
    if (!title.toLowerCase().startsWith("chore: release v")) {
      console.log("Not a release PR title; skipping.");
      return;
    }

    const baseRef = pr.base?.ref || "";
    const headRef = pr.head?.ref || "";

    // Optional sanity check: base should look like a tag. If it doesn't, still comment but warn.
    const baseLooksLikeTag = baseRef.startsWith("release-v") && /\d+\.\d+\.\d+/.test(baseRef);
    
    const issue_number = pr.number;
    if (await commentAlreadyExists({ github, owner, repo, issue_number })) {
      console.log("Marker comment already exists; not posting again.");
      return;
    }

    const prompt = loadPrompt();

    const body = buildBody({ prompt, baseRef, headRef, baseLooksLikeTag });

    await github.rest.issues.createComment({
      owner,
      repo,
      issue_number,
      body,
    });

    console.log("Posted CodeRabbit release-gate comment.");
    console.log(`PR #${issue_number} (${headRef} → ${baseRef})`);
  } catch (error) {
    console.error(`Error in release PR coderabbit gate: ${error.message}`);
    console.log(`PR #${issue_number || 'unknown'} (${headRef || '?'} → ${baseRef || '?'})`);
  }
};