Add community PR limit workflow

.github/scripts/pr_limit_moderation.js

@@ -0,0 +1,163 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+function getPullRequest(context) {
+  const pullRequest = context.payload.pull_request;
+  if (!pullRequest?.number || !pullRequest.user?.login) {
+    throw new Error('This script must be run from a pull_request_target event.');
+  }
+
+  return {
+    author: pullRequest.user.login,
+    labels: pullRequest.labels?.map((label) => label.name).filter(Boolean) ?? [],
+    number: pullRequest.number,
+  };
+}
+
+async function ensureLabel({ github, owner, repo, labelName }) {
+  try {
+    await github.rest.issues.getLabel({
+      owner,
+      repo,
+      name: labelName,
+    });
+  } catch (error) {
+    if (error.status !== 404) {
+      throw error;
+    }
+
+    try {
+      await github.rest.issues.createLabel({
+        owner,
+        repo,
+        name: labelName,
+        color: 'd93f0b',
+        description: 'Community author has exceeded the open pull request limit.',
+      });
+    } catch (createError) {
+      if (createError.status !== 422) {
+        throw createError;
+      }
+    }
+  }
+}
+
+function hasLabel(labels, labelName) {
+  if (!labelName) {
+    return false;
+  }
+
+  return labels.some((label) => label.toLowerCase() === labelName.toLowerCase());
+}
+
+function buildLimitMessage({ author, exemptLabelName, maxOpenPrs, openPrCount }) {
+  return [
+    `Thank you for your contribution, @${author}.`,
+    '',
+    `To keep the review queue manageable, we currently limit community contributors to ${maxOpenPrs} `
+      + `open pull requests at a time. This PR would put you at ${openPrCount} open pull requests, `
+      + 'so we are closing it automatically.',
+    '',
+    'Please focus on getting your existing PRs reviewed, merged, or closed before opening another one. '
+      + `If a maintainer asked you to open this PR, they can apply the \`${exemptLabelName}\` label and reopen it.`,
+  ].join('\n');
+}
+
+async function getOpenPrCount({ github, owner, repo, author, pullRequestNumber }) {
+  const query = `repo:${owner}/${repo} is:pr is:open author:${author}`;
+  const response = await github.rest.search.issuesAndPullRequests({
+    q: query,
+    per_page: 100,
+  });
+
+  const indexedPrNumbers = response.data.items.map((item) => item.number);
+  const currentPrIsIndexed = indexedPrNumbers.includes(pullRequestNumber);
+  if (currentPrIsIndexed || response.data.total_count >= 100) {
+    return response.data.total_count;
+  }
+
+  return response.data.total_count + 1;
+}
+
+async function enforcePrLimit({ github, context, core, exemptLabelName, maxOpenPrs, labelName }) {
+  const { owner, repo } = context.repo;
+  const { author, labels, number } = getPullRequest(context);
+
+  if (hasLabel(labels, exemptLabelName)) {
+    core.info(`PR #${number} has the ${exemptLabelName} label; skipping open PR limit enforcement.`);
+    return {
+      author,
+      closed: false,
+      exempt: true,
+      openPrCount: null,
+    };
+  }
+
+  const openPrCount = await getOpenPrCount({
+    github,
+    owner,
+    repo,
+    author,
+    pullRequestNumber: number,
+  });
+
+  if (openPrCount <= maxOpenPrs) {
+    core.info(
+      `${author} has ${openPrCount} open pull request(s), which is within the limit of ${maxOpenPrs}.`,
+    );
+    return {
+      author,
+      closed: false,
+      openPrCount,
+    };
+  }
+
+  await ensureLabel({
+    github,
+    owner,
+    repo,
+    labelName,
+  });
+
+  await github.rest.issues.addLabels({
+    owner,
+    repo,
+    issue_number: number,
+    labels: [labelName],
+  });
+
+  await github.rest.issues.createComment({
+    owner,
+    repo,
+    issue_number: number,
+    body: buildLimitMessage({
+      author,
+      exemptLabelName,
+      maxOpenPrs,
+      openPrCount,
+    }),
+  });
+
+  await github.rest.pulls.update({
+    owner,
+    repo,
+    pull_number: number,
+    state: 'closed',
+  });
+
+  core.info(
+    `${author} has ${openPrCount} open pull request(s), which exceeds the limit of ${maxOpenPrs}. `
+      + `Closed PR #${number}.`,
+  );
+
+  return {
+    author,
+    closed: true,
+    openPrCount,
+  };
+}
+
+module.exports = {
+  buildLimitMessage,
+  enforcePrLimit,
+  getOpenPrCount,
+};