feat: Add feature flags with PostHog integration (ESM)#2160
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Rebase of PR hackforla#2096 onto current development branch, with all code converted from CommonJS to ESM to match the codebase's module system. Backend changes: - Add FeatureFlagsController with custom header validation - Add FeatureFlagsService wrapping posthog-node client - Add featureFlags router with addCookieIfAvailable middleware - Add addCookieIfAvailable to auth middleware (optional JWT decode) - Register featureFlags route in app.js - Add posthog-node dependency - Bump Dockerfile.api to node:22 - Add controller test using vitest (converted from jest) - Add services/index.js barrel export Client changes: - Add FeatureFlagProvider context with useFeatureFlags hook - Add featureFlagApiService for fetching flags - Wrap App with FeatureFlagProvider - Initialize posthog-js in index.jsx - Add posthog.identify in authContext fetchAuth - Add posthog-js dependency Other: - Add .env.test to .gitignore Original PR: hackforla#2096
- Expand controller tests: header validation, distinctId fallback, response body - Add service tests: PostHog SDK wrapper, error propagation - Add middleware tests: addCookieIfAvailable JWT handling - Add router integration tests: route wiring, middleware chain - Add client tests: API service fetch params, context provider lifecycle Generated with [Claude Code](https://claude.ai/code) via [Happy](https://happy.engineering) Co-Authored-By: Claude <noreply@anthropic.com> Co-Authored-By: Happy <yesreply@happy.engineering>
Cut tests that verify JavaScript operators, Express internals, or duplicate assertions already covered by other tests. Generated with [Claude Code](https://claude.ai/code) via [Happy](https://happy.engineering) Co-Authored-By: Claude <noreply@anthropic.com> Co-Authored-By: Happy <yesreply@happy.engineering>
Previous lockfile had parse errors causing Docker build failures in CI. Generated with [Claude Code](https://claude.ai/code) via [Happy](https://happy.engineering) Co-Authored-By: Claude <noreply@anthropic.com> Co-Authored-By: Happy <yesreply@happy.engineering>
- Backend unit: replace --testPathIgnorePatterns (Jest) with test:unit script using vitest --exclude - Backend integration: replace 'backend/routers/' path filter (wrong cwd inside Docker) with test:integration script using relative paths - Client: remove USER node from client-development Dockerfile stage to fix EACCES when Vite writes temp config files in mounted volume Generated with [Claude Code](https://claude.ai/code) via [Happy](https://happy.engineering) Co-Authored-By: Claude <noreply@anthropic.com> Co-Authored-By: Happy <yesreply@happy.engineering>
- Mount ./shared:/srv/shared in docker-compose so backend container can resolve '../../shared/authorizationUtils.js' imports - Use vi.hoisted() to set CUSTOM_REQUEST_HEADER before controller module loads, fixing false 400 when env var is unset in CI Generated with [Claude Code](https://claude.ai/code) via [Happy](https://happy.engineering) Co-Authored-By: Claude <noreply@anthropic.com> Co-Authored-By: Happy <yesreply@happy.engineering>
Generated with [Claude Code](https://claude.ai/code) via [Happy](https://happy.engineering) Co-Authored-By: Claude <noreply@anthropic.com> Co-Authored-By: Happy <yesreply@happy.engineering>
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Feature Flags with PostHog Integration (ESM)
Rebases and resolves merge conflicts from #2096 by @kkchu791 onto current
development, with full ESM conversion and expanded test coverage.Background
@kkchu791 built out a feature flags system using PostHog in #2096. That PR developed merge conflicts after the backend ESM migration (#2134) landed on
development. This PR carries his work forward — all the feature flag logic is his design, we just resolved the conflicts, converted to ESM, and added tests.What's included
Feature flags system (@kkchu791's work from #2096):
featureFlags.service.js— wraps PostHoggetAllFlags(distinctId)featureFlags.controller.js— validates custom header, resolves user identity, returns flagsfeatureFlags.router.js—GET /api/featureFlagswith optional auth middlewareaddCookieIfAvailablemiddleware — optional JWT parsing for personalized flagsFeatureFlagProvidercontext +useFeatureFlagshookposthog.identify()on auth for user-level flag targetingConflict resolution + ESM conversion:
require()/module.exports→import/export.jsextensions on relative importsTest coverage (new):
All 109 backend tests and 15 client tests passing.
Credit
All feature flag implementation is @kkchu791's work from #2096. This PR resolves the merge conflicts from the ESM migration and adds test coverage.
Closes #2096