Comment changeset status in PRs (#625)

* Initial implementation

* Fix

* fix

* fix

* Make it look nicer

* Update docs

* Rename to pr-status-comment

* Remove outputs

* Update path

* update name

* Checkout PR in a detached worktree (#626)

Co-authored-by: bluwy <bjornlu.dev@gmail.com>

* Move comment to separate job

* Loosen event requirement

* Update

* Apply suggestions from code review

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

* Use TLA

* use using

* Remove test log

---------

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

src/pr-status/index.ts

@@ -0,0 +1,23 @@
+import * as core from "@actions/core";
+import * as github from "@actions/github";
+import { getCommentMessage } from "./message.ts";
+
+try {
+  await main();
+} catch (err) {
+  core.setFailed((err as Error).message);
+}
+
+async function main() {
+  const context = github.context.payload.pull_request;
+  if (!context) {
+    throw new Error(
+      "This action should only be run on `pull_request_target` or `pull_request` events",
+    );
+  }
+
+  core.info("Creating comment message...");
+  const commentBody = await getCommentMessage(context);
+  core.setOutput("comment-body", commentBody);
+  core.info("Done!");
+}

src/pr-status/message.ts

@@ -0,0 +1,120 @@
+import * as github from "@actions/github";
+import getReleasePlan from "@changesets/get-release-plan";
+import type {
+  ComprehensiveRelease,
+  ReleasePlan,
+  VersionType,
+} from "@changesets/types";
+import { markdownTable } from "markdown-table";
+import {
+  getNewChangesetTemplateContent,
+  getNewChangesetUrl,
+} from "./template.ts";
+import { getPullRequestWorktree } from "./worktree.ts";
+
+type PullRequestContext = NonNullable<
+  typeof github.context.payload.pull_request
+>;
+
+export async function getCommentMessage(context: PullRequestContext) {
+  await using worktree = await getPullRequestWorktree(context);
+
+  const releasePlan = await getReleasePlan(worktree.cwd, worktree.baseRef);
+  const templateContent = await getNewChangesetTemplateContent(
+    worktree.cwd,
+    worktree.baseRef,
+    context.title,
+  );
+
+  const newChangesetUrl = getNewChangesetUrl(
+    context.head.repo.html_url,
+    context.head.ref,
+    templateContent,
+  );
+
+  if (releasePlan.changesets.length > 0) {
+    return getApproveMessage(context.head.sha, newChangesetUrl, releasePlan);
+  } else {
+    return getAbsentMessage(context.head.sha, newChangesetUrl, releasePlan);
+  }
+}
+
+function getApproveMessage(
+  commitSha: string,
+  newChangesetUrl: string,
+  releasePlan: ReleasePlan,
+) {
+  return `\
+### 🦋 Changeset detected
+
+Latest commit: ${commitSha}
+
+**The changes in this PR will be included in the next version bump.**
+
+${getReleasePlanMessage(releasePlan)}
+
+Not sure what this means? [Click here to learn what changesets are](https://github.com/changesets/changesets/blob/main/docs/adding-a-changeset.md).
+
+[Click here if you're a maintainer who wants to add another changeset to this PR](${newChangesetUrl})`;
+}
+
+function getAbsentMessage(
+  commitSha: string,
+  newChangesetUrl: string,
+  releasePlan: ReleasePlan,
+) {
+  return `\
+### ⚠️ No Changeset found
+
+Latest commit: ${commitSha}
+
+Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. **If these changes should result in a version bump, you need to add a changeset.**
+
+${getReleasePlanMessage(releasePlan)}
+
+[Click here to learn what changesets are, and how to add one](https://github.com/changesets/changesets/blob/main/docs/adding-a-changeset.md).
+
+[Click here if you're a maintainer who wants to add a changeset to this PR](${newChangesetUrl})`;
+}
+
+function getReleasePlanMessage(releasePlan: ReleasePlan) {
+  const publishableReleases = releasePlan.releases.filter(
+    (r) => r.type !== "none",
+  ) as (ComprehensiveRelease & { type: Exclude<VersionType, "none"> })[];
+
+  const table = markdownTable([
+    ["Name", "Type"],
+    ...publishableReleases.map((release) => {
+      return [
+        release.name,
+        {
+          major: "Major",
+          minor: "Minor",
+          patch: "Patch",
+        }[release.type],
+      ];
+    }),
+  ]);
+
+  let summary = "This PR includes ";
+  if (releasePlan.changesets.length === 0) {
+    summary += "no changesets";
+  } else {
+    summary += `changesets to release ${publishableReleases.length} package`;
+    if (publishableReleases.length !== 1) {
+      summary += "s";
+    }
+  }
+
+  return `\
+<details>
+<summary>${summary}</summary>
+
+${
+  publishableReleases.length > 0
+    ? table
+    : "When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types"
+}
+
+</details>`;
+}

src/pr-status/template.ts

@@ -0,0 +1,30 @@
+import { getChangedPackagesSinceRef } from "@changesets/git";
+import { humanId } from "human-id";
+
+export function getNewChangesetUrl(
+  headRepoUrl: string,
+  headRef: string,
+  templateContent: string,
+) {
+  const fileName = humanId({ separator: "-", capitalize: false });
+  return `${headRepoUrl}/new/${headRef}?filename=.changeset/${fileName}.md&value=${encodeURIComponent(templateContent)}`;
+}
+
+export async function getNewChangesetTemplateContent(
+  cwd: string,
+  baseRef: string,
+  prTitle: string,
+) {
+  const changedPackages = await getChangedPackagesSinceRef({
+    cwd,
+    ref: baseRef,
+  });
+
+  return `\
+---
+${changedPackages.map((p) => `"${p.packageJson.name}": patch`).join("\n")}
+---
+
+${prTitle}
+`;
+}

src/pr-status/worktree.test.ts

@@ -0,0 +1,148 @@
+import { pathToFileURL } from "node:url";
+import type * as github from "@actions/github";
+import getReleasePlan from "@changesets/get-release-plan";
+import { createFixture } from "fs-fixture";
+import { exec } from "tinyexec";
+import { describe, expect, it } from "vitest";
+import { getPullRequestWorktree } from "./worktree.ts";
+
+type PullRequestContext = NonNullable<
+  typeof github.context.payload.pull_request
+>;
+
+async function git(cwd: string, args: string[]) {
+  const output = await exec("git", args, {
+    nodeOptions: { cwd },
+    throwOnError: true,
+  });
+  return output.stdout.trim();
+}
+
+describe("getPullRequestWorktree", () => {
+  it("fetches a PR branch into a detached worktree and keeps the main checkout untouched", async () => {
+    // Local source repo
+    await using sourceRepoFixture = await createFixture({
+      ".changeset/config.json": JSON.stringify({}),
+      "package.json": JSON.stringify({
+        name: "repo",
+        private: true,
+        workspaces: ["packages/*"],
+      }),
+      "packages/pkg-a/package.json": JSON.stringify({
+        name: "pkg-a",
+        version: "1.0.0",
+      }),
+    });
+    const sourceRepo = sourceRepoFixture.path;
+    await git(sourceRepo, ["init", "-b", "main"]);
+    await git(sourceRepo, ["config", "user.name", "Test User"]);
+    await git(sourceRepo, ["config", "user.email", "test@example.com"]);
+    await git(sourceRepo, ["add", "."]);
+    await git(sourceRepo, ["commit", "-m", "base"]);
+
+    // Simulate remote bare git server
+    await using originBareFixture = await createFixture();
+    const originBare = originBareFixture.path;
+    await git(originBare, ["clone", "--bare", sourceRepo, originBare]);
+
+    // Simulate checkout PR in github action
+    await using checkoutRepoFixture = await createFixture();
+    const checkoutRepo = checkoutRepoFixture.path;
+    await git(checkoutRepo, [
+      "clone",
+      "--depth",
+      "1",
+      "--branch",
+      "main",
+      pathToFileURL(originBare).toString(),
+      checkoutRepo,
+    ]);
+
+    // Simulate remote fork bare git server
+    await using forkBareFixture = await createFixture();
+    const forkBare = forkBareFixture.path;
+    await git(forkBare, ["clone", "--bare", originBare, forkBare]);
+
+    await using forkRepoFixture = await createFixture();
+    const forkRepo = forkRepoFixture.path;
+    await git(forkRepo, [
+      "clone",
+      "--depth",
+      "1",
+      "--branch",
+      "main",
+      pathToFileURL(forkBare).toString(),
+      forkRepo,
+    ]);
+    await git(forkRepo, ["config", "user.name", "Test User"]);
+    await git(forkRepo, ["config", "user.email", "test@example.com"]);
+    await git(forkRepo, ["checkout", "-b", "feature"]);
+
+    await forkRepoFixture.mkdir("packages/pkg-a/src");
+    await forkRepoFixture.writeFile(
+      "packages/pkg-a/src/index.ts",
+      "export const value = 1;\n",
+    );
+    await forkRepoFixture.writeFile(
+      ".changeset/add-pkg-a.md",
+      `\
+---
+"pkg-a": patch
+---
+
+Add pkg-a
+`,
+    );
+
+    await git(forkRepo, ["add", "."]);
+    await git(forkRepo, ["commit", "-m", "feature"]);
+    await git(forkRepo, ["push", "origin", "feature"]);
+
+    // Run tests
+    const originalHead = await git(checkoutRepo, ["rev-parse", "HEAD"]);
+    const context = {
+      number: 123,
+      base: {
+        ref: "main",
+        repo: {
+          clone_url: pathToFileURL(originBare).toString(),
+        },
+      },
+      head: {
+        ref: "feature",
+        repo: {
+          clone_url: pathToFileURL(forkBare).toString(),
+        },
+      },
+    };
+
+    await using worktree = await getPullRequestWorktree(
+      context satisfies PullRequestContext as PullRequestContext,
+      checkoutRepo,
+    );
+
+    const releasePlan = await getReleasePlan(worktree.cwd, worktree.baseRef);
+
+    const currentHead = await git(worktree.cwd, ["rev-parse", "HEAD"]);
+    expect(currentHead).not.toBe(originalHead);
+
+    const currentBranch = await git(worktree.cwd, ["branch", "--show-current"]);
+    expect(currentBranch).toBe("");
+
+    const releases = releasePlan.releases.map((release) => ({
+      name: release.name,
+      type: release.type,
+      newVersion: release.newVersion,
+    }));
+    expect(releases).toEqual([
+      {
+        name: "pkg-a",
+        type: "patch",
+        newVersion: "1.0.1",
+      },
+    ]);
+
+    expect(await git(checkoutRepo, ["rev-parse", "HEAD"])).toBe(originalHead);
+    expect(await git(checkoutRepo, ["branch", "--show-current"])).toBe("main");
+  });
+});

src/pr-status/worktree.ts

@@ -0,0 +1,165 @@
+import { randomUUID } from "node:crypto";
+import fs from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import type * as github from "@actions/github";
+import { isRepoShallow } from "@changesets/git";
+import { exec } from "tinyexec";
+
+type PullRequestContext = NonNullable<
+  typeof github.context.payload.pull_request
+>;
+
+type WorktreeInfo = {
+  baseRef: string;
+  cwd: string;
+};
+
+type TinyexecOptions = Parameters<typeof exec>[2];
+
+function git(cwd: string, args: string[], opts: TinyexecOptions = {}) {
+  return exec("git", args, {
+    nodeOptions: { cwd, ...opts.nodeOptions },
+    throwOnError: true,
+    ...opts,
+  });
+}
+
+interface Ref {
+  fetchSource: string;
+  local: string;
+  remote: string;
+}
+
+function getRefs(context: PullRequestContext): Record<"base" | "head", Ref> {
+  const suffix = `${context.number}-${randomUUID()}`;
+  return {
+    base: {
+      fetchSource: "origin",
+      local: `refs/changesets-action-pr-status/base/${suffix}`,
+      remote: `refs/heads/${context.base.ref}`,
+    },
+    head: {
+      fetchSource: context.head.repo.clone_url,
+      local: `refs/changesets-action-pr-status/head/${suffix}`,
+      remote: `refs/heads/${context.head.ref}`,
+    },
+  };
+}
+
+async function deepenRef(cwd: string, ref: Ref, deepenBy: number) {
+  await git(cwd, [
+    "fetch",
+    "--no-tags",
+    `--deepen=${deepenBy}`,
+    ref.fetchSource,
+    `${ref.remote}:${ref.local}`,
+  ]);
+}
+
+async function ensureMergeBase(args: {
+  cwd: string;
+  refs: ReturnType<typeof getRefs>;
+  deepenBy?: number;
+}) {
+  const { cwd, refs, deepenBy = 50 } = args;
+
+  while (true) {
+    const mergeBase = await git(cwd, ["merge-base", refs.base.local, "HEAD"], {
+      throwOnError: false,
+    });
+
+    if (mergeBase.exitCode === 0) {
+      return mergeBase.stdout.trim();
+    }
+
+    if (!(await isRepoShallow({ cwd }))) {
+      throw new Error(
+        `Failed to find merge base between "${refs.base.local}" and HEAD, and the repository is no longer shallow.`,
+      );
+    }
+
+    await deepenRef(cwd, refs.base, deepenBy);
+    await deepenRef(cwd, refs.head, deepenBy);
+  }
+}
+
+async function mkdtemp(prefix: string) {
+  const dir = await fs.mkdtemp(path.join(os.tmpdir(), prefix));
+
+  return {
+    dir,
+    async [Symbol.asyncDispose]() {
+      await fs.rm(dir, { recursive: true, force: true });
+    },
+  };
+}
+
+async function tempRef(cwd: string, ref: Ref) {
+  await git(cwd, [
+    "fetch",
+    "--no-tags",
+    "--depth=1",
+    ref.fetchSource,
+    `${ref.remote}:${ref.local}`,
+  ]);
+  return {
+    async [Symbol.asyncDispose]() {
+      await git(cwd, ["update-ref", "-d", ref.local], { throwOnError: false });
+    },
+  };
+}
+
+async function tempWorktree(cwd: string, dir: string, ref: Ref) {
+  await git(cwd, ["worktree", "add", "--detach", dir, ref.local]);
+
+  return {
+    async [Symbol.asyncDispose]() {
+      await git(cwd, ["worktree", "remove", "--force", dir], {
+        throwOnError: false,
+      });
+    },
+  };
+}
+
+type WithAsyncDispose<T> = T & {
+  [Symbol.asyncDispose](): Promise<void>;
+};
+
+function moveDisposable<T extends object>(
+  stack: AsyncDisposableStack,
+  value: T,
+): WithAsyncDispose<T> {
+  const moved = stack.move();
+  return Object.assign(value, {
+    async [Symbol.asyncDispose]() {
+      await moved.disposeAsync();
+    },
+  });
+}
+
+export async function getPullRequestWorktree(
+  context: PullRequestContext,
+  cwd: string = process.cwd(),
+): Promise<WithAsyncDispose<WorktreeInfo>> {
+  await using stack = new AsyncDisposableStack();
+  const worktreeDir = stack.use(
+    await mkdtemp("changesets-action-pr-status-"),
+  ).dir;
+
+  const refs = getRefs(context);
+
+  stack.use(await tempRef(cwd, refs.base));
+  stack.use(await tempRef(cwd, refs.head));
+  stack.use(await tempWorktree(cwd, worktreeDir, refs.head));
+
+  await ensureMergeBase({
+    cwd: worktreeDir,
+    refs,
+  });
+
+  return moveDisposable(stack, {
+    baseRef: refs.base.local,
+    cwd: worktreeDir,
+  });
+}