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>

.changeset/wacky-taxis-sink.md

@@ -0,0 +1,5 @@
+---
+"@changesets/action": minor
+---
+
+Add a new `@changesets/action/pr-status` sub-action to generate the changeset status comment for PRs as an alternative to the [Changesets Bot](https://github.com/apps/changeset-bot).

README.md

@@ -2,6 +2,10 @@
 
 This action for [Changesets](https://github.com/changesets/changesets) creates a pull request with all of the package versions updated and changelogs updated and when there are new changesets on [your configured `baseBranch`](https://github.com/changesets/changesets/blob/main/docs/config-file-options.md#basebranch-git-branch-name), the PR will be updated. When you're ready, you can merge the pull request and you can either publish the packages to npm manually or setup the action to do it for you.
 
+There are also sub-actions hosted in this repository. Check out their respective READMEs for more details:
+
+- [pr-status](./pr-status/README.md): Generate changeset status in PRs.
+
 ## Usage
 
 ### Inputs

package.json

@@ -20,13 +20,18 @@
     "@actions/core": "^3.0.1",
     "@actions/exec": "^3.0.0",
     "@actions/github": "^9.1.1",
+    "@changesets/get-release-plan": "^4.0.16",
     "@changesets/ghcommit": "^2.0.1",
+    "@changesets/git": "^3.0.4",
     "@changesets/pre": "^2.0.2",
     "@changesets/read": "^0.6.7",
     "@manypkg/get-packages": "^1.1.3",
     "@octokit/core": "^7.0.6",
     "@octokit/plugin-throttling": "^11.0.3",
-    "semver": "^7.8.0"
+    "human-id": "^4.1.3",
+    "markdown-table": "^3.0.4",
+    "semver": "^7.8.0",
+    "tinyexec": "^1.1.2"
   },
   "devDependencies": {
     "@changesets/changelog-github": "^0.7.0",

pnpm-lock.yaml

@@ -22,9 +22,15 @@ importers:
       '@actions/github':
         specifier: ^9.1.1
         version: 9.1.1
+      '@changesets/get-release-plan':
+        specifier: ^4.0.16
+        version: 4.0.16
       '@changesets/ghcommit':
         specifier: ^2.0.1
         version: 2.0.1
+      '@changesets/git':
+        specifier: ^3.0.4
+        version: 3.0.4
       '@changesets/pre':
         specifier: ^2.0.2
         version: 2.0.2
@@ -40,9 +46,18 @@ importers:
       '@octokit/plugin-throttling':
         specifier: ^11.0.3
         version: 11.0.3(@octokit/core@7.0.6)
+      human-id:
+        specifier: ^4.1.3
+        version: 4.1.3
+      markdown-table:
+        specifier: ^3.0.4
+        version: 3.0.4
       semver:
         specifier: ^7.8.0
         version: 7.8.0
+      tinyexec:
+        specifier: ^1.1.2
+        version: 1.1.2
     devDependencies:
       '@changesets/changelog-github':
         specifier: ^0.7.0
@@ -874,6 +889,9 @@ packages:
   magic-string@0.30.21:
     resolution: {integrity: sha512-vd2F4YUyEXKGcLHoq+TEyCjxueSeHnFxyyjNp80yg0XV4vUhnDer/lvvlqM/arB5bXQN5K2/3oinyCRyx8T2CQ==}
 
+  markdown-table@3.0.4:
+    resolution: {integrity: sha512-wiYz4+JrLyb/DqW2hkFJxP7Vd7JuTDm77fvbM8VfEQdmSMqcImWeeRbHwZjBjIFki/VaMK2BhFi7oUUZeM5bqw==}
+
   math-intrinsics@1.1.0:
     resolution: {integrity: sha512-/IXtbwEk5HTPyEwyKX6hGkYXxM9nbj64B+ilVJnC/R6B0pH5G4V3b0pVbL7DBj4tkhBAppbQUlf6F6Xl9LHu1g==}
     engines: {node: '>= 0.4'}
@@ -2063,6 +2081,8 @@ snapshots:
     dependencies:
       '@jridgewell/sourcemap-codec': 1.5.5
 
+  markdown-table@3.0.4: {}
+
   math-intrinsics@1.1.0: {}
 
   merge2@1.4.1: {}

pr-status/README.md

@@ -0,0 +1,62 @@
+# changesets/action/pr-status
+
+This action generates the changesets status in PRs, e.g. whether it has changeset files and which packages will be released if the PR is merged.
+
+It requires the repo to be checked out, and automatically fetches the PR head ref into a temporary detached worktree in order to infer the changed files and packages. It also requires the [`pull_request_target`](https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows#pull_request_target) event to be triggered in order to have permissions to comment on the PR and to work in PRs from forks.
+
+You can also use the [`pull_request`](https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows#pull_request) event if you prefer to lock permissions down and not run for PRs from forks. Make sure to add an if check to prevent the action from failing in fork PRs:
+
+```yaml
+jobs:
+  pr-status:
+    if: github.event.pull_request.head.repo.full_name == github.repository
+    # ...
+```
+
+See the [action metadata](action.yml) for details on the inputs and outputs.
+
+> [!WARNING]
+> **Do not run untrusted code** when using the `pull_request_target` event. The example below only checks out code and does not run any code from the PR. Read more about the `pull_request_target` event in the [GitHub documentation](https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows#pull_request_target).
+
+## Example setup
+
+```yaml
+# .github/workflows/comment-changesets-pr-status.yml
+name: Comment Changesets status in PRs
+
+on:
+  pull_request_target:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  pr-status:
+    runs-on: ubuntu-slim
+    permissions:
+      contents: read # to check out files in the repo
+    outputs:
+      comment-body: ${{ steps.pr-status.outputs.comment-body }}
+    steps:
+      - name: Check out repo
+        uses: actions/checkout@v6
+
+      - name: Generate status
+        id: pr-status
+        uses: changesets/action/pr-status@v1
+
+  pr-comment:
+    needs: pr-status
+    runs-on: ubuntu-slim
+    permissions:
+      pull-requests: write # to create and update comments on PRs
+    steps:
+      - name: Comment on PR
+        uses: changesets/action/pr-comment@v1
+        with:
+          body: ${{ needs.pr-status.outputs.comment-body }}
+          update-id: changesets-pr-status
+```
+
+The workflow uses [`@changesets/action/pr-comment`](../pr-comment/README.md), which is a simple GitHub Action to comment on PRs.

pr-status/action.yml

@@ -0,0 +1,12 @@
+name: Changesets - PR Status
+description: Generate the changesets status in PRs
+runs:
+  using: node24
+  main: ../dist/pr-status.js
+inputs: {}
+outputs:
+  comment-body:
+    description: The generated comment body to present the changesets status in PRs.
+branding:
+  icon: package
+  color: blue

rolldown.config.js

@@ -1,7 +1,10 @@
 import { defineConfig } from "rolldown";
 
 export default defineConfig({
-  input: "src/index.ts",
+  input: {
+    index: "src/index.ts",
+    ["pr-status"]: "src/pr-status/index.ts",
+  },
   output: {
     dir: "dist",
     format: "esm",

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,
+  });
+}