From 9f8775671dd8cc84aface34abdef2d83bfde432a Mon Sep 17 00:00:00 2001
From: Petri Lehtinen <petri.lehtinen@reaktor.com>
Date: Tue, 5 Nov 2024 08:45:23 +0200
Subject: [PATCH] Add a CI workflow that validates PR labels

---
 .github/workflows/validate-labels.yml | 21 +++++++++++
 bin/validate-labels.js                | 54 +++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 .github/workflows/validate-labels.yml
 create mode 100755 bin/validate-labels.js

diff --git a/.github/workflows/validate-labels.yml b/.github/workflows/validate-labels.yml
new file mode 100644
index 00000000000..9a84310299a
--- /dev/null
+++ b/.github/workflows/validate-labels.yml
@@ -0,0 +1,21 @@
+# SPDX-FileCopyrightText: 2017-2024 City of Espoo
+#
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+name: 'Validate PR labels'
+on:
+  pull_request:
+    types:
+      - labeled
+      - unlabeled
+      - opened
+      - reopened
+      - ready_for_review
+
+jobs:
+  validate-labels:
+    if: ${{ github.event.pull_request.state == 'open' && !github.event.pull_request.draft }}
+    runs-on: ubuntu-latest
+    steps:
+      - run: |
+          echo '${{ toJSON(github.event.pull_request.labels[*].name) }}' | bin/validate-labels.js
diff --git a/bin/validate-labels.js b/bin/validate-labels.js
new file mode 100755
index 00000000000..70030559e4b
--- /dev/null
+++ b/bin/validate-labels.js
@@ -0,0 +1,54 @@
+#!/usr/bin/env node
+
+// SPDX-FileCopyrightText: 2017-2024 City of Espoo
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
+// Usage:
+//
+// echo '["foo", "bar"]' | bin/check-labels.js
+//
+
+function main() {
+  let inputData = ''
+
+  const stdin = process.stdin;
+  stdin.setEncoding('utf-8')
+  stdin.on('data', (data) => {
+      inputData += data
+  });
+
+  stdin.on('end', () => {
+    let json
+    try {
+        json = JSON.parse(inputData);
+    } catch (error) {
+        console.error('An error occurred while parsing JSON:', error.message);
+        process.exit(1);
+    }
+    if (!validateLabels(json)) {
+      console.error('Each pull request must have exactly one of the following labels:', knownLabels.join(', '));
+      process.exit(1);
+    }
+  });
+}
+
+const knownLabels = [
+  'no-changelog',
+  'breaking',
+  'enhancement',
+  'bug',
+  'unknown',
+  'tech',
+  'dependencies'
+];
+
+function validateLabels(labels) {
+  const numKnownLabels = labels.reduce(
+    (acc, label) => (knownLabels.includes(label)) ? acc + 1 : acc,
+    0
+  );
+  return numKnownLabels === 1;
+}
+
+main();