ci: limit pull requests to maintainers and an allowlist of invited authors

.github/pr-authors.txt

@@ -0,0 +1,7 @@
+# Logins allowed to open pull requests, one per line, matched case-insensitively.
+# Repository owners, members and collaborators, and bots, are always allowed.
+lancy69
+chuiwenwei
+xxoingr
+kevin9327
+imcreazy

.github/pull_request_template.md

@@ -2,6 +2,9 @@
 Target branch: 2.x features and fixes go to `studio`. 1.x takes bug fixes,
 provider/API compatibility, release/updater, security and platform stability
 only, on `main-v2`.
+
+Pull requests are limited to maintainers and invited contributors; one from
+anyone else is closed automatically. Open an issue instead.
 -->
 
 ## Summary

.github/workflows/pr-author-gate.yml

@@ -0,0 +1,27 @@
+name: PR author gate
+
+# Pull requests are limited to maintainers and the logins in .github/pr-authors.txt.
+# This runs in the base repository's context, checks out the base branch only, and
+# never executes pull-request code; the allowlist it reads is the base branch's.
+on:
+  pull_request_target:
+    types: [opened]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+concurrency:
+  group: pr-author-gate-${{ github.event.pull_request.number }}
+  cancel-in-progress: false
+
+jobs:
+  gate:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
+      - run: node scripts/pr-author-gate.mjs
+        env:
+          GH_TOKEN: ${{ github.token }}

scripts/pr-author-gate.mjs

@@ -0,0 +1,45 @@
+#!/usr/bin/env node
+// Closes a newly opened pull request whose author is not on the allowlist.
+import { spawnSync } from "node:child_process";
+import { readFileSync } from "node:fs";
+import { pathToFileURL } from "node:url";
+
+const MAINTAINERS = new Set(["OWNER", "MEMBER", "COLLABORATOR"]);
+
+export function parseAllowlist(text) {
+  return new Set(text.split("\n").map((line) => line.trim()).filter((line) => line && !line.startsWith("#"))
+    .map((login) => login.toLowerCase()));
+}
+
+export function decide({ association, authorType, login, allowed }) {
+  if (authorType === "Bot" || MAINTAINERS.has(association)) return "allow";
+  return allowed.has(login.toLowerCase()) ? "allow" : "close";
+}
+
+export const CLOSING_COMMENT = `Thanks for wanting to contribute. Pull requests are currently limited to the maintainers and a small set of invited contributors, so this one has been closed automatically; nothing is wrong with it.
+
+Please open an issue instead (a bug report with the steps to reproduce is the most useful). A maintainer will look at it, and if you would like to fix it yourself, say so there: if a maintainer agrees, this pull request can be reopened.`;
+
+function gh(args, input) {
+  const result = spawnSync("gh", args, { encoding: "utf8", input, maxBuffer: 4 * 1024 * 1024 });
+  if (result.status !== 0) throw new Error(`gh ${args[0]} ${args[1]} failed: ${result.stderr}`);
+  return result.stdout;
+}
+
+export function run({ event, repository, allowlist, exec = gh, log = console.log }) {
+  const pr = event.pull_request;
+  const verdict = decide({
+    association: pr.author_association, authorType: pr.user.type, login: pr.user.login, allowed: parseAllowlist(allowlist),
+  });
+  log(`#${pr.number} by ${pr.user.login} (${pr.author_association}): ${verdict}`);
+  if (verdict === "allow") return verdict;
+  exec(["pr", "comment", String(pr.number), "--repo", repository, "--body-file", "-"], CLOSING_COMMENT);
+  exec(["pr", "close", String(pr.number), "--repo", repository]);
+  return verdict;
+}
+
+if (process.argv[1] && import.meta.url === pathToFileURL(process.argv[1]).href) {
+  const event = JSON.parse(readFileSync(process.env.GITHUB_EVENT_PATH, "utf8"));
+  const allowlist = readFileSync(new URL("../.github/pr-authors.txt", import.meta.url), "utf8");
+  run({ event, repository: process.env.GITHUB_REPOSITORY, allowlist });
+}

scripts/pr-author-gate.test.mjs

@@ -0,0 +1,58 @@
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import test from "node:test";
+import { CLOSING_COMMENT, decide, parseAllowlist, run } from "./pr-author-gate.mjs";
+
+const allowlist = "# comment\nLancy69\n\n  kevin9327  \n";
+const event = (login, association = "NONE", type = "User") => ({
+  pull_request: { number: 7, author_association: association, user: { login, type } },
+});
+const harness = () => {
+  const calls = [];
+  return { calls, exec: (args, input) => { calls.push({ args, input }); return ""; } };
+};
+const go = (e, h) => run({ event: e, repository: "o/r", allowlist, exec: h.exec, log: () => {} });
+
+test("the allowlist ignores comments and blanks and matches case-insensitively", () => {
+  assert.deepEqual([...parseAllowlist(allowlist)], ["lancy69", "kevin9327"]);
+  assert.equal(go(event("LANCY69", "CONTRIBUTOR"), harness()), "allow");
+  assert.equal(go(event("kevin9327", "FIRST_TIME_CONTRIBUTOR"), harness()), "allow");
+});
+
+for (const association of ["OWNER", "MEMBER", "COLLABORATOR"]) {
+  test(`${association} is never gated`, () => {
+    const h = harness();
+    assert.equal(go(event("maintainer", association), h), "allow");
+    assert.deepEqual(h.calls, []);
+  });
+}
+
+test("a bot such as dependabot is never gated", () => {
+  const h = harness();
+  assert.equal(go(event("dependabot[bot]", "NONE", "Bot"), h), "allow");
+  assert.deepEqual(h.calls, []);
+});
+
+for (const association of ["CONTRIBUTOR", "FIRST_TIME_CONTRIBUTOR", "FIRST_TIMER", "NONE", "MANNEQUIN"]) {
+  test(`${association} who is not on the list is commented and closed, whatever their history`, () => {
+    const h = harness();
+    assert.equal(go(event("someone-else", association), h), "close");
+    assert.deepEqual(h.calls.map((c) => c.args.slice(0, 3)), [["pr", "comment", "7"], ["pr", "close", "7"]]);
+    assert.equal(h.calls[0].input, CLOSING_COMMENT);
+  });
+}
+
+test("decide admits only maintainers, bots and listed logins", () => {
+  const allowed = new Set(["a"]);
+  assert.equal(decide({ association: "NONE", authorType: "User", login: "A", allowed }), "allow");
+  assert.equal(decide({ association: "CONTRIBUTOR", authorType: "User", login: "b", allowed }), "close");
+});
+
+test("the shipped allowlist parses and the workflow is safe", () => {
+  assert.ok(parseAllowlist(readFileSync(new URL("../.github/pr-authors.txt", import.meta.url), "utf8")).size >= 1);
+  const text = readFileSync(new URL("../.github/workflows/pr-author-gate.yml", import.meta.url), "utf8");
+  assert.match(text, /pull_request_target:\n\s+types: \[opened\]/);
+  assert.doesNotMatch(text, /head\.(sha|ref)|refs\/pull/);
+  assert.match(text, /permissions:\n\s+contents: read\n\s+pull-requests: write/);
+  assert.match(text, /node scripts\/pr-author-gate\.mjs/);
+});