ci: validate PRs with build and MDX heading linter (#743)

* ci: validate PRs with build and MDX heading linter

Adds a pull_request workflow running npm run lint:mdx, npm run build,
and npm run lint so heading-hierarchy bugs and broken builds get caught
before merge rather than after.

The new linter (scripts/lint-mdx-headings.mjs) enforces that the first
heading is h1 and that heading levels never jump by more than one. Also
fixes three existing pages that had no h1 title — two were using a
legacy export const title pattern, one was missing a title entirely.

* ci: use npm install since lockfile is gitignored

package-lock.json is in .gitignore, so npm ci and setup-node's npm
cache both fail on a fresh CI checkout. Match the Dockerfile pattern
(npm install, no cache) instead.

* ci: drop ESLint step; project config is broken

`npm run lint` fails with 'Converting circular structure to JSON'
under ESLint 9.x — the repo has no .eslintrc or eslint.config file,
so the legacy resolver hits the React plugin's circular reference.
This is pre-existing (build_n_push.yml never ran lint, so it stayed
hidden); fixing it needs flat-config migration and is out of scope.
Drop the step until that lands.

.github/workflows/pr-build.yml

@@ -0,0 +1,33 @@
+name: pr-build
+on: [pull_request]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ github.head_ref || github.actor_id }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: lint and build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Lint MDX heading hierarchy
+        run: npm run lint:mdx
+
+      - name: Build
+        run: npm run build

package.json

@@ -11,7 +11,8 @@
     "gen": "swagger-codegen generate -i https://raw.githubusercontent.com/netbirdio/netbird/main/management/server/http/api/openapi.yml -l openapi -o generator/openapi && npx ts-node generator/index.ts gen --input generator/openapi/openapi.json --output src/pages/ipa/resources",
     "gen:llm": "node scripts/generate-llm-docs.mjs",
     "start": "next start",
-    "lint": "eslint src/"
+    "lint": "eslint src/",
+    "lint:mdx": "node scripts/lint-mdx-headings.mjs"
   },
   "browserslist": {
     "production": [

scripts/lint-mdx-headings.mjs

@@ -0,0 +1,97 @@
+#!/usr/bin/env node
+/**
+ * Lints MDX files for heading-hierarchy violations:
+ *   - the first heading on a page must be h1 (the page title)
+ *   - heading levels may not jump by more than 1 going down (h1 -> h3 is invalid; h3 -> h1 is fine)
+ *
+ * Skips src/pages/ipa/resources/ — those are auto-generated from the OpenAPI spec.
+ * Headings inside fenced code blocks are ignored.
+ */
+
+import fs from 'fs'
+import path from 'path'
+import { fileURLToPath } from 'url'
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url))
+const ROOT = path.join(__dirname, '..')
+const PAGES_DIR = path.join(ROOT, 'src/pages')
+const SKIP_PREFIX = 'ipa/resources'
+
+function findMdxFiles(dir, basePath = '') {
+  const entries = fs.readdirSync(dir, { withFileTypes: true })
+  const results = []
+  for (const e of entries) {
+    const rel = basePath ? `${basePath}/${e.name}` : e.name
+    if (e.isDirectory()) {
+      if (rel === SKIP_PREFIX || rel.startsWith(`${SKIP_PREFIX}/`)) continue
+      results.push(...findMdxFiles(path.join(dir, e.name), rel))
+    } else if (e.name.endsWith('.mdx')) {
+      results.push({ relPath: rel, filePath: path.join(dir, e.name) })
+    }
+  }
+  return results
+}
+
+function checkHeadings(content) {
+  const lines = content.split('\n')
+  const violations = []
+  let inCodeBlock = false
+  let prevLevel = 0
+  let prevLine = 0
+
+  for (let i = 0; i < lines.length; i++) {
+    const line = lines[i]
+    if (/^```/.test(line)) {
+      inCodeBlock = !inCodeBlock
+      continue
+    }
+    if (inCodeBlock) continue
+
+    const match = /^(#{1,6})\s+(.+?)\s*$/.exec(line)
+    if (!match) continue
+
+    const level = match[1].length
+    const text = match[2]
+
+    if (prevLevel === 0) {
+      if (level !== 1) {
+        violations.push({
+          line: i + 1,
+          message: `first heading is h${level} ("${text}"); expected h1`,
+        })
+      }
+    } else if (level > prevLevel + 1) {
+      violations.push({
+        line: i + 1,
+        message: `h${level} ("${text}") skips a level (previous was h${prevLevel} on line ${prevLine})`,
+      })
+    }
+
+    prevLevel = level
+    prevLine = i + 1
+  }
+
+  return violations
+}
+
+const files = findMdxFiles(PAGES_DIR)
+let totalViolations = 0
+
+for (const { relPath, filePath } of files) {
+  const content = fs.readFileSync(filePath, 'utf-8')
+  const violations = checkHeadings(content)
+  if (violations.length > 0) {
+    console.error(`\nsrc/pages/${relPath}`)
+    for (const v of violations) {
+      console.error(`  line ${v.line}: ${v.message}`)
+    }
+    totalViolations += violations.length
+  }
+}
+
+if (totalViolations > 0) {
+  console.error(`\n${totalViolations} heading hierarchy violation(s) found.`)
+  process.exit(1)
+}
+
+console.log(`Checked ${files.length} MDX files — no heading hierarchy violations.`)

src/pages/about-netbird/other.mdx

@@ -1,6 +1,6 @@
 import {Note} from "@/components/mdx";
 
-export const title = 'Other'
+# Other
 
 ## Google Summer of Code Ideas - 2022
 

src/pages/about-netbird/understanding-nat-and-connectivity.mdx

@@ -1,6 +1,6 @@
 import {Note} from "@/components/mdx";
 
-export const title = 'Understanding NAT and Connectivity'
+# Understanding NAT and Connectivity
 
 ## What is NAT?
 

src/pages/manage/integrations/kubernetes/client-sidecar.mdx

@@ -1,4 +1,4 @@
-## Client Sidecar
+# Client Sidecar
 
 In certain situations we may want to have a pod act like a peer in the Netbird network instead of exposing it through a routing peer. In these cases a Netbird client container has to be added as a sidecar to the pod.