Added core functionality to auto-merge PRs (#5)

Created base of the bot, with the ability to comment on a PR and to
enable/disable auto-merge.

You can find a working example in paritytech-stg#1

This resolves #1 

The bot can enable auto-merge, disable it and show the available
commands.

If the user is not a member of the org or the author of the PR, the bot
will not work. This is to stop external parties of enabling/disabling
the bot.

This is a required step to solve polkadot-fellows/runtimes#41

---------

Co-authored-by: Przemek Rzad <[email protected]>

.github/workflows/auto-merge-bot.yml

@@ -0,0 +1,17 @@
+name: Auto Merge Bot
+
+on:
+ # GitHub considers PRs as issues
+ issue_comment:
+ types: [created]
+
+jobs:
+ set-auto-merge:
+ runs-on: ubuntu-latest
+ # Important! This forces the job to run only on Pull Requests
+ if: ${{ github.event.issue.pull_request && startsWith(github.event.comment.body, '/bot') }}
+ steps:
+ - name: Set auto merge
+ uses: paritytech/auto-merge-bot@main
+ with:
+ GITHUB_TOKEN: '${{ github.token }}'

README.md

@@ -1,9 +1,58 @@
-# Parity GitHub Action template
+# Auto-Merge-Bot
 
-Template used to generate GitHub Actions.
+Bot which enables or disable [`auto-merge`](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/incorporating-changes-from-a-pull-request/automatically-merging-a-pull-request) in a repository.
 
-## To start
+## Why?
 
-- Remember to modify the `action.yml` file to have your required attributes and details. 
- - You can use [GitHub Action Brandings cheatsheet](https://github.com/haya14busa/github-action-brandings) to set the style of the action.
-- Remember to modify the name in the `package.json`.
+This action was developed to help external parties merge their own Pull Requests.
+
+If an external party makes a PR, and it is approved, they still can not merge it. This bot gives them the ability to enable the `auto-merge` function so, once their PR gets approved, it is merged.
+
+## Configuration
+Be sure that **Allow auto-merge** is enabled in the repository options.
+
+Create a file named `.github/workflows/auto-merge-bot.yml` and add the following:
+```yaml
+name: Auto Merge Bot
+
+on:
+ # GitHub considers PRs as issues
+ issue_comment:
+ types: [created]
+
+jobs:
+ set-auto-merge:
+ runs-on: ubuntu-latest
+ # Important! This forces the job to run only on comments on Pull Requests that starts with '/bot'
+ if: ${{ github.event.issue.pull_request && startsWith(github.event.comment.body, '/bot') }}
+ steps:
+ - name: Set auto merge
+ uses: paritytech/auto-merge-bot@main
+ with:
+ GITHUB_TOKEN: '${{ github.token }}'
+ MERGE_METHOD: "SQUASH"
+```
+
+#### Inputs
+You can find all the inputs in [the action file](./action.yml), but let's walk through each one of them:
+
+- `GITHUB_TOKEN`: Token to access to the repository.
+ - **required**
+ - This is provided by the repo, you can simply use `${{ github.token }}`.
+- `MERGE_METHOD`: Type of merge to enable.
+ - **Optional**: Defaults to `SQUASH`.
+ - Available types are `MERGE`, `REBASE` and `SQUASH`.
+ - Make sure that the type of merge you selected is available in the repository merge options.
+
+## Usage
+
+To trigger the bot, you need to write a comment in a Pull Request where the action is installed. The available actions are:
+- `/bot merge`: Enables auto-merge for Pull Request
+- `/bot cancel`: Cancels auto-merge for Pull Request
+- `/bot help`: Shows this menu
+
+The bot can only be triggered by the author of the PR or by users who *publicly* belongs to the organization of the repository.
+
+By publicly, I refer to the members of an organization which can be seen by external parties. If you are not sure if you are part of an organization, simply open https://github.com/orgs/**your_organization**/people in a private window. If you don’t see your name there, you are not a public member.
+
+Find related docs here: [ Publicizing or hiding organization membership](https://docs.github.com/en/account-and-profile/setting-up-and-managing-your-personal-account-on-github/managing-your-membership-in-organizations/publicizing-or-hiding-organization-membership).

action.yml

@@ -1,13 +1,17 @@
-name: "Example Action"
-description: "This values need to be changed"
+name: "Auto Merge Bot"
+description: "Bot which enables or disable auto-merge"
 author: Bullrich
 branding:
- icon: copy
- color: yellow
+ icon: git-merge
+ color: red
 inputs:
  GITHUB_TOKEN:
  required: true
- description: The token to access the repo
+ description: The token to access the repo information
+ MERGE_METHOD:
+ required: false
+ description: The merge method to use. Must be one of MERGE, SQUASH or REBASE.
+ default: SQUASH
 outputs:
  repo:
  description: 'The name of the repo in owner/repo pattern'

package.json

@@ -1,7 +1,7 @@
 {
- "name": "parity-action-template",
+ "name": "auto-merge-bot",
  "version": "0.0.1",
- "description": "GitHub action template for Parity",
+ "description": "Bot which enables or disable auto-merge",
  "main": "src/index.ts",
  "scripts": {
  "start": "node dist",
@@ -12,17 +12,19 @@
  },
  "repository": {
  "type": "git",
- "url": "git+https://github.com/Bullrich/parity-action-template.git"
+ "url": "git+https://github.com/paritytech/auto-merge-bot.git"
  },
  "author": "Javier Bullrich <[email protected]>",
  "license": "MIT",
  "bugs": {
- "url": "https://github.com/Bullrich/parity-action-template/issues"
+ "url": "https://github.com/paritytech/auto-merge-bot/issues"
  },
- "homepage": "https://github.com/Bullrich/parity-action-template#readme",
+ "homepage": "https://github.com/paritytech/auto-merge-bot#readme",
  "dependencies": {
  "@actions/core": "^1.10.1",
  "@actions/github": "^5.1.1",
+ "@octokit/graphql": "^7.0.2",
+ "@octokit/graphql-schema": "^14.32.1",
  "@octokit/webhooks-types": "^7.3.1"
  },
  "devDependencies": {

src/bot.ts

@@ -0,0 +1,107 @@
+import { Issue, IssueComment } from "@octokit/webhooks-types";
+
+import { CommentsApi } from "./github/comments";
+import { Merger } from "./github/merger";
+import { ActionLogger } from "./github/types";
+
+const BOT_COMMAND = "/bot";
+
+type Command = "merge" | "cancel" | "help";
+
+const botCommands = `
+**Available commands**
+
+- \`/bot merge\`: Enables auto-merge for Pull Request
+- \`/bot cancel\`: Cancels auto-merge for Pull Request
+- \`/bot help\`: Shows this menu
+
+For more information see the [documentation](https://github.com/paritytech/auto-merge-bot)
+`;
+
+export class Bot {
+ constructor(
+ private readonly comment: IssueComment,
+ private readonly pr: Issue,
+ private readonly logger: ActionLogger,
+ private readonly commentsApi: CommentsApi,
+ ) {}
+
+ /** Verifies if the author is the author of the PR or a member of the org */
+ async canTriggerBot(): Promise<boolean> {
+ this.logger.debug("Evaluating if user can trigger the bot");
+ const author = this.pr.user.id;
+ if (this.comment.user.id === author) {
+ this.logger.debug("Author of comment is also author of PR");
+ return true;
+ }
+ this.logger.debug("Author of comment is not the author of the PR");
+
+ return await this.commentsApi.userBelongsToOrg(this.comment.user.login);
+ }
+
+ async run(merger: Merger): Promise<void> {
+ this.logger.info("Running action on comment: " + this.comment.html_url);
+ if (!this.comment.body.startsWith(BOT_COMMAND)) {
+ this.logger.info(
+ `Ignoring comment ${this.comment.html_url} as it does not start with '${BOT_COMMAND}'`,
+ );
+ return;
+ }
+
+ if (this.pr.state === "closed") {
+ this.logger.info("Ignoring PR as it is closed");
+ return;
+ }
+
+ if (!(await this.canTriggerBot())) {
+ const { login } = this.comment.user;
+ const org = this.commentsApi.pullData.owner;
+ this.logger.warn(
+ "User is not allowed to trigger the bot. " +
+ `He is not the author of the PR and does not *publicly* belong to the org: https://github.com/orgs/${org}/people`,
+ );
+ await this.commentsApi.reactToComment(this.comment.id, "-1");
+ await this.commentsApi.comment(
+ "## Auto-Merge-Bot\n" +
+ `User @${login} is not the author of the PR and does not [*publicly* belong to the org \`${org}\`](https://github.com/orgs/${org}/people).\n\n` +
+ "Only author or *public* org members can trigger the bot.",
+ );
+ return;
+ }
+ this.logger.debug("User can trigger bot");
+
+ const [_, command] = this.comment.body.split(" ");
+ try {
+ switch (command as Command) {
+ case "merge":
+ await this.commentsApi.reactToComment(this.comment.id, "+1");
+ await merger.enableAutoMerge();
+ await this.commentsApi.comment(
+ "Enabled `auto-merge` in Pull Request",
+ );
+ break;
+ case "cancel":
+ await this.commentsApi.reactToComment(this.comment.id, "+1");
+ await merger.disableAutoMerge();
+ await this.commentsApi.comment(
+ "Disabled `auto-merge` in Pull Request",
+ );
+ break;
+ case "help":
+ await this.commentsApi.comment("## Auto-Merge-Bot\n" + botCommands);
+ break;
+ default: {
+ await this.commentsApi.reactToComment(this.comment.id, "confused");
+ await this.commentsApi.comment(
+ "## Auto-Merge-Bot\n" +
+ `Command \`${command}\` not recognized.\n\n` +
+ botCommands,
+ );
+ }
+ }
+ } catch (e) {
+ this.logger.error(e as Error);
+ throw e;
+ }
+ }
+}

src/github/comments.ts

@@ -0,0 +1,47 @@
+import { ActionLogger, GitHubClient } from "./types";
+
+/** API class that uses the default token to access the data from the pull request and the repository */
+export class CommentsApi {
+ constructor(
+ private readonly api: GitHubClient,
+ private readonly logger: ActionLogger,
+ public readonly pullData: { repo: string; owner: string; number: number },
+ ) {}
+
+ async comment(message: string): Promise<void> {
+ await this.api.rest.issues.createComment({
+ ...this.pullData,
+ body: message,
+ issue_number: this.pullData.number,
+ });
+ }
+
+ async reactToComment(
+ commentId: number,
+ reaction: "+1" | "-1" | "confused",
+ ): Promise<void> {
+ await this.api.rest.reactions.createForIssueComment({
+ ...this.pullData,
+ comment_id: commentId,
+ content: reaction,
+ });
+ }
+
+ async userBelongsToOrg(username: string): Promise<boolean> {
+ const org = this.pullData.owner;
+ this.logger.debug(
+ `Checking if user ${username} belongs to ${org} as a public user.`,
+ );
+ // If the user does not belong to the org, this will throw an http error
+ try {
+ const { status } = await this.api.rest.orgs.checkPublicMembershipForUser({
+ org,
+ username,
+ });
+ return status === 204;
+ } catch (error) {
+ this.logger.warn(error as Error);
+ return false;
+ }
+ }
+}

src/github/merger.ts

@@ -0,0 +1,50 @@
+import { graphql } from "@octokit/graphql";
+import { PullRequestMergeMethod } from "@octokit/graphql-schema";
+
+import { ActionLogger } from "./types";
+
+// https://docs.github.com/en/graphql/reference/mutations#enablepullrequestautomerge
+export const ENABLE_AUTO_MERGE = `
+mutation($prId: ID!, $mergeMethod: PullRequestMergeMethod!) {
+ enablePullRequestAutoMerge(input: {pullRequestId: $prId, mergeMethod: $mergeMethod}) {
+ clientMutationId
+ }
+}`;
+
+// https://docs.github.com/en/graphql/reference/mutations#disablepullrequestautomerge
+export const DISABLE_AUTO_MERGE = `
+mutation($prId: ID!) {
+ disablePullRequestAutoMerge(input: {pullRequestId: $prId}) {
+ clientMutationId
+ }
+}`;
+
+export type MergeMethod = "SQUASH" | "MERGE" | "REBASE";
+
+export class Merger {
+ constructor(
+ private readonly nodeId: string,
+ private readonly gql: typeof graphql,
+ private readonly logger: ActionLogger,
+ private readonly mergeMethod: PullRequestMergeMethod,
+ ) {}
+
+ async enableAutoMerge(): Promise<void> {
+ await this.gql<{
+ enablePullRequestAutoMerge: { clientMutationId: unknown };
+ }>(ENABLE_AUTO_MERGE, {
+ prId: this.nodeId,
+ mergeMethod: this.mergeMethod,
+ });
+ this.logger.info("Succesfully enabled auto-merge");
+ }
+
+ async disableAutoMerge(): Promise<void> {
+ await this.gql<{
+ disablePullRequestAutoMerge: { clientMutationId: unknown };
+ }>(DISABLE_AUTO_MERGE, {
+ prId: this.nodeId,
+ });
+ this.logger.info("Succesfully disabled auto-merge");
+ }
+}