feat(analytics): upload source maps to PostHog on production builds

Wrap the Next.js config with @posthog/nextjs-config (outermost wrapper,
required for its build hooks to run) so client source maps are uploaded
to PostHog and deleted from the build output afterwards.

Upload is enabled only when POSTHOG_API_KEY and POSTHOG_PROJECT_ID are
set and SKIP_ENV_VALIDATION is not (Nix sandbox builds have no network):
the plugin throws at config-load time if enabled without credentials,
which would otherwise break dev and deploy builds missing the env vars.

Author: christosporios

.env.example

@@ -116,3 +116,10 @@ BASIC_AUTH_PASSWORD=
 # EU cloud project token (public by design, shipped to the browser).
 # Leave empty to disable analytics entirely.
 NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN=
+
+# Source map upload on production builds (optional).
+# Personal API key (secret) and numeric project ID; leave empty to skip uploading.
+POSTHOG_API_KEY=
+POSTHOG_PROJECT_ID=
+# PostHog instance the source maps are uploaded to, e.g. https://eu.i.posthog.com
+NEXT_PUBLIC_POSTHOG_HOST=

next.config.mjs

@@ -1,5 +1,6 @@
 import './src/env.mjs';
 import createNextIntlPlugin from 'next-intl/plugin';
+import { withPostHogConfig } from "@posthog/nextjs-config";
 
 // Log which DB the build will use (host + db name only, no credentials)
 try {
@@ -84,5 +85,19 @@ const nextConfig = {
     skipTrailingSlashRedirect: true,
 };
 
-export default withNextIntl(nextConfig);
+export default withPostHogConfig(withNextIntl(nextConfig), {
+    personalApiKey: process.env.POSTHOG_API_KEY,
+    projectId: process.env.POSTHOG_PROJECT_ID,
+    host: process.env.NEXT_PUBLIC_POSTHOG_HOST,
+    sourcemaps: {
+        // SKIP_ENV_VALIDATION=1 is set in Nix sandbox builds where network is blocked.
+        // Disable there to prevent upload failures; production (DO App Platform) uses npm run build directly.
+        // The plugin throws at config-load time if enabled without credentials, so also
+        // require them to be present (contributors without a .env.local, deploys without the vars).
+        enabled: !process.env.SKIP_ENV_VALIDATION
+            && !!process.env.POSTHOG_API_KEY
+            && !!process.env.POSTHOG_PROJECT_ID,
+        deleteAfterUpload: true,
+    },
+});
 

package-lock.json

@@ -55,6 +55,7 @@
     "@mapbox/mapbox-gl-draw": "^1.5.0",
     "@mux/mux-video": "^0.20.2",
     "@mux/mux-video-react": "^0.26.1",
+    "@posthog/nextjs-config": "^1.9.68",
     "@prisma/client": "^5.22.0",
     "@radix-ui/react-checkbox": "^1.1.1",
     "@radix-ui/react-collapsible": "^1.1.0",