PR hygiene checking (#910)

* pr lint check

Fixes #782

* undo

* ignore more

* remove env.GIT_DIFF

* only context

* run it

* remove env.GIT_DIFF

* unbreak cache

* updates

* updates

* all types

* set -e

* don't catch

* set -e needed?

* debugging

* better errors

* testing

* testing

* using returns

* using returns

* last cleanup

* remove debug

* touchups

* touchups

* remove emojis

* remove the need for the PR description to be filled in

.github/workflows/pr-lint.yml

@@ -0,0 +1,30 @@
+# Checks the PR itself for hygiene things.
+
+name: PR Lint
+
+on:
+  pull_request:
+    # Necessary to re-run if someone edits the PR without a new pushed commit.
+    types: [opened, edited, synchronize, reopened]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup Node.js environment
+        uses: actions/setup-node@v2.1.4
+        with:
+          node-version: "12"
+
+      - name: Install all yarn packages
+        run: |
+          cd pr-lint
+          yarn --frozen-lockfile
+
+      - name: Run checks
+        run: |
+          cd pr-lint
+          yarn run check

.gitignore

@@ -1,4 +1,5 @@
 /node_modules
+/pr-lint/node_modules/
 /build
 .env
 yarn-debug.log*

pr-lint/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "pr-lint",
+  "version": "1.0.0",
+  "main": "src/index.js",
+  "license": "SEE LICENSE IN LICENSE.md",
+  "engines": {
+    "node": ">=12.0.0"
+  },
+  "scripts": {
+    "check": "node src/index.js"
+  },
+  "dependencies": {
+    "@actions/github": "4.0.0",
+    "boxen": "5.0.0"
+  }
+}

pr-lint/src/index.js

@@ -0,0 +1,63 @@
+const boxen = require("boxen");
+const github = require("@actions/github");
+
+async function main() {
+  // TODO: Consider being super friendly and possibly...
+  //  * Post a comment that is friendly and useful that explains the problems.
+  //  * Just edit the PR title (or whatever it is) if it's easily fixable.
+  // See https://www.npmjs.com/package/@actions/github for documentation
+  // about how to use @actions/github to do authenticated things.
+  const context = github.context;
+
+  const contextPullRequest = context.payload.pull_request;
+  if (!contextPullRequest) {
+    throw new Error(
+      "This action can only be invoked in `pull_request` events. Otherwise the pull request can't be inferred."
+    );
+  }
+
+  const { title } = contextPullRequest;
+  if (title === "Update index.html") {
+    // This is the default title you get when you use the GitHub UI to
+    // edit a file and following web form steps to create a PR.
+    // These PRs are hard to triage and to organize because of the
+    // rather "useless" title so let's put the onus back on the author
+    // to come up with a better title.
+    // See https://github.com/mdn/content/issues/782
+    return (
+      'Pull request title can\'t just be "Update index.html"\n' +
+      "Please update the pull request to be more descriptive. " +
+      "For example 'fix typo on Web/JavaScript'."
+    );
+  }
+
+  // No errors or problems!
+  return null;
+}
+
+main()
+  .then((ret) => {
+    if (ret) {
+      const lines = ret.split("\n");
+      console.log(
+        boxen(lines[0], { padding: 1, margin: 1, borderStyle: "double" })
+      );
+      // Because boxen breaks, in GitHub Actions logging, when multiple lines.
+      if (lines.length > 1) {
+        console.log(`\n${lines.slice(1).join("\n")}\n`);
+      }
+      process.exitCode = 2;
+    } else {
+      console.log(
+        boxen("Happiness is when nothing's wrong!", {
+          padding: 1,
+          margin: 1,
+          borderStyle: "double",
+        })
+      );
+    }
+  })
+  .catch((error) => {
+    console.error(error);
+    process.exitCode = 1;
+  });