feat(registry): add PostHog analytics script #568
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- Add useScriptPostHog composable using npm package pattern - Add posthog-js as optional peer dependency - Support US/EU region configuration - Add common config options (autocapture, capturePageview, etc.) - Add documentation with usage examples 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
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Move state management to window object to handle HMR correctly and prevent shared state issues across multiple useScriptPostHog calls. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
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src/runtime/registry/posthog.ts
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| use() { | ||
| return window.posthog ? { posthog: window.posthog } : undefined | ||
| }, | ||
| }, | ||
| clientInit: import.meta.server | ||
| ? undefined | ||
| : () => { | ||
| // Use window for state to handle HMR correctly | ||
| if (window.__posthogInitPromise || window.posthog) | ||
| return |
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The use() function checks if window.posthog exists synchronously, but the clientInit function starts an asynchronous import operation that completes later. If use() is called before the async initialization finishes, it will return undefined, causing proxy.posthog to be undefined.
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📝 Patch Details
diff --git a/src/runtime/registry/posthog.ts b/src/runtime/registry/posthog.ts
index b7b5e87..bc738b6 100644
--- a/src/runtime/registry/posthog.ts
+++ b/src/runtime/registry/posthog.ts
@@ -27,6 +27,7 @@ declare global {
}
export function useScriptPostHog<T extends PostHogApi>(_options?: PostHogInput) {
+ let readyPromise: Promise<PostHog | undefined> = Promise.resolve(undefined)
return useRegistryScript<T, typeof PostHogOptions>('posthog', options => ({
scriptInput: {
src: '', // No external script - using npm package
@@ -34,7 +35,7 @@ export function useScriptPostHog<T extends PostHogApi>(_options?: PostHogInput)
schema: import.meta.dev ? PostHogOptions : undefined,
scriptOptions: {
use() {
- return window.posthog ? { posthog: window.posthog } : undefined
+ return { posthog: window.posthog! }
},
},
clientInit: import.meta.server
@@ -44,6 +45,30 @@ export function useScriptPostHog<T extends PostHogApi>(_options?: PostHogInput)
if (window.__posthogInitPromise || window.posthog)
return
+ // Initialize a queue/stub synchronously to avoid race conditions
+ // This ensures use() always returns a valid object
+ const queue: Array<{ method: string, args: any[] }> = []
+ const stub: any = new Proxy({}, {
+ get: (target, method: string | symbol) => {
+ if (typeof method !== 'string')
+ return undefined
+ return (...args: any[]) => {
+ // Queue the call if the real posthog hasn't loaded yet
+ if (!window.posthog || window.posthog === stub) {
+ queue.push({ method, args })
+ return
+ }
+ // Once loaded, call the real method
+ const fn = (window.posthog as any)[method]
+ if (typeof fn === 'function') {
+ return fn.apply(window.posthog, args)
+ }
+ }
+ },
+ })
+
+ window.posthog = stub as any as PostHog
+
const region = options?.region || 'us'
const apiHost = region === 'eu'
? 'https://eu.i.posthog.com'
@@ -64,8 +89,22 @@ export function useScriptPostHog<T extends PostHogApi>(_options?: PostHogInput)
config.disable_session_recording = options.disableSessionRecording
window.posthog = posthog.init(options?.apiKey || '', config)
+
+ // Replay queued calls
+ for (const { method, args } of queue) {
+ const fn = (window.posthog as any)[method]
+ if (typeof fn === 'function') {
+ fn.apply(window.posthog, args)
+ }
+ }
+
return window.posthog
+ }).then((result) => {
+ readyPromise = Promise.resolve(result)
+ return result
})
+
+ readyPromise = window.__posthogInitPromise
},
}), _options)
}
Analysis
Race condition between async initialization and synchronous use() in PostHog integration
What fails: The useScriptPostHog() composable's use() function returns undefined if called before the asynchronous import('posthog-js') completes, preventing the proxy mechanism from functioning correctly.
How to reproduce:
// In a Vue component:
const { proxy } = useScriptPostHog({ apiKey: 'test-key' })
// Immediately call PostHog method
proxy.posthog.capture('event') // Fails with "Cannot read properties of undefined"The issue occurs because:
clientInit()starts an asyncimport('posthog-js')operation that setswindow.posthoglateruse()is called synchronously by the proxy mechanism to get the API reference- If
use()is called before the import completes,window.posthogdoesn't exist yet use()returnsundefined, breaking the proxy system which relies on a valid object reference
Result: Calls to proxy methods fail if made before async initialization completes. The proxy system from @unhead/vue relies on the use() function returning a valid object reference to queue calls.
Expected behavior: The use() function should always return a valid object, similar to other analytics scripts like Crisp (see src/runtime/registry/crisp.ts) which initialize a stub synchronously.
Fix: Initialize window.posthog as a queuing stub synchronously in clientInit(), then replace it with the real PostHog instance once the async import completes. Calls made before initialization are queued and replayed after the library loads.
- Use consistent logger.warn instead of console.warn - Fix documentation to show correct config schema (record not object) - Validate posthog.init() return value before assignment - Clear queue on initialization failure to prevent memory leak - Add detailed comments for queue flushing logic
…flags - Add test fixture page that tests event capture, user identification, and feature flags - Create mock PostHog API endpoint to simulate /decide and /batch responses - Test event capture with custom properties - Test user identification with profile data - Test feature flag checks with isFeatureEnabled - Test feature flag payload retrieval with getFeatureFlagPayload - Verify all PostHog functionality works end-to-end with queue flushing
- Remove mock API endpoints in favor of real PostHog cloud - Use test project API key: phc_CkMaDU6dr11eJoQdAiSJb1rC324dogk3T952gJ6fD9W - Configure person_profiles: 'identified_only' as recommended - Update test assertions to verify client-side behavior - Feature flags now tested against real PostHog /decide endpoint - Events sent to real PostHog for actual end-to-end validation - Add debug logging for feature flag values in test output
- Component initializes but never mounts - Status stuck at awaitingLoad - Need to debug browser console for actual runtime error
- PostHog initializes successfully but status goes to 'error' - Added extensive debug logging throughout initialization - Removed scriptInput then added back with src: false - TypeScript error: src expects string not boolean - Need to investigate proper way to handle NPM-only scripts
…or workaround) PostHog is fully functional but status shows 'error' due to @nuxt/scripts not properly supporting NPM-only integrations. The integration works because: - clientInit properly initializes posthog-js via dynamic import - Proxy queues calls until PostHog is ready - E2E tests wait for window.posthog instead of status - Events, identification, and feature flags all work correctly This is a known limitation with NPM-based scripts in @nuxt/scripts. Potential future fix: Add support for scriptInput-less integrations.
- Created createNpmScriptStub for scripts without external CDN URLs - Added scriptMode option: 'external' (default) or 'npm' - NPM mode properly manages lifecycle: await Loading → loading → loaded - onLoaded callbacks fire correctly for NPM scripts - Updated PostHog to use scriptMode: 'npm' (removes src: '' workaround) - clientInit now returns promise for proper lifecycle tracking This fixes the status=error issue for PostHog and enables proper feature flag support via on Loaded callbacks.
- PostHog now uses scriptMode: 'npm' - Removed src: '' workaround - clientInit returns promise for proper lifecycle - Ready for E2E testing once dev server dependencies are fixed
| @@ -0,0 +1,110 @@ | |||
| <script setup lang="ts"> | |||
| import type { PostHog } from 'posthog-js' | |||
| import { watch, onMounted } from 'vue' | |||
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Suggested change
| import { watch, onMounted } from 'vue' | |
| import { watch, onMounted, ref } from 'vue' | |
| import { useScriptPostHog } from '#imports' |
The file uses useScriptPostHog without explicitly importing it, which is inconsistent with the codebase pattern used in other test fixtures.
View Details
Analysis
Missing imports in test/fixtures/basic/pages/tpc/posthog.vue
What fails: The component uses useScriptPostHog and ref without explicitly importing them, which is inconsistent with established patterns in other test fixtures in the same directory
How to reproduce:
# Check other test fixtures in the same directory
cat test/fixtures/basic/pages/tpc/ga.vue # Imports from '#imports'
cat test/fixtures/basic/pages/tpc/recaptcha.vue # Imports from '#imports'
cat test/fixtures/basic/pages/tpc/posthog.vue # Missing imports (before fix)Result: While Nuxt's auto-imports feature allows the code to compile and run, the pattern is inconsistent with:
ga.vuewhich importsuseScriptGoogleAnalyticsfrom'#imports'recaptcha.vuewhich importsuseScriptGoogleRecaptchafrom'#imports'
The file also uses ref without importing it, though other files that use ref explicitly import it either from 'vue' or '#imports'.
Expected: Imports should be explicit and consistent with the established pattern across the test fixtures, as documented in the Nuxt style guide
Fix applied: Added explicit imports:
reffrom'vue'(to match Vue's composition API pattern)useScriptPostHogfrom'#imports'(to match other test fixtures in the same directory)
Prevents window access during server-side rendering. NPM script mode now fully functional: - Status correctly transitions to 'loaded' - onLoaded callbacks fire properly - Feature flags work via real PostHog API - Event capture and identification working Tested and verified in browser.
- Added ref import to PostHog test fixture - Moved trigger option to scriptOptions (correct nesting) - Added onNuxtReady string trigger support to npm-script-stub - Removed explicit useScriptPostHog import (auto-imported by Nuxt) All E2E tests passing.
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