feat(billing): emit subscription_changed analytics on plan change (#3769)

PierreBrisorgueil · web-flow · commit c860b0fe0fc8 · 2026-06-01T21:37:37.000+02:00
- Add AnalyticsService.isConfigured() to lib/services/analytics.js - Guard analytics emit with isConfigured() — no-op on downstreams without PostHog; non-fatal try/catch protects webhook processing - New unit test: 5 cases (plan change, isDowngrade, not-configured no-op, same-plan no-emit, stale-event no-emit) Restores trawl observability lost in /update-stack #1316. Promoted to devkit: AnalyticsService is a devkit-level abstraction. Cross-ref: trawl#1315, infra plan 2026-06-01-trawl-promote-up-followups
diff --git a/lib/services/analytics.js b/lib/services/analytics.js
@@ -235,6 +235,16 @@ const getFeatureFlagForRequest = async (flag, req, options) =>
 const isFeatureEnabledForRequest = async (flag, req, options) =>
   isFeatureEnabled(flag, resolveDistinctId(req), options);
 
+/**
+ * Return whether the PostHog client is currently initialised.
+ * Use this as a cheap pre-check before building expensive analytics payloads.
+ * The underlying `capture()` and `track()` methods are already no-ops when
+ * the client is absent — `isConfigured()` is for callers that want to skip
+ * payload construction entirely when analytics is not active.
+ * @returns {boolean}
+ */
+const isConfigured = () => client !== null;
+
 /**
  * Flush pending events and shut down the PostHog client.
  * Safe to call even when the client was never initialised.
@@ -249,6 +259,7 @@ const shutdown = async () => {
 
 export default {
   init,
+  isConfigured,
   track,
   capture,
   identify,
diff --git a/modules/billing/services/billing.webhook.service.js b/modules/billing/services/billing.webhook.service.js
@@ -16,6 +16,7 @@ import billingEvents from '../lib/events.js';
 import { SENTINEL_PENDING } from '../lib/billing.constants.js';
 import { retryWithBackoff } from '../lib/billing.retry.js';
 import { isNonTransientStripeError } from '../lib/billing.stripe-errors.js';
+import AnalyticsService from '../../../lib/services/analytics.js';
 
 /**
  * Treats a stripeSessionId as "unresolved" when absent, empty, or still the
@@ -506,6 +507,28 @@ const handleSubscriptionUpdated = async (subscription, event) => {
         });
       }
 
+      // Emit analytics observability event for downstreams running PostHog (no-op otherwise).
+      // Mirrors the internal billing.plan.changed event but lands in the analytics pipeline.
+      if (AnalyticsService.isConfigured()) {
+        try {
+          AnalyticsService.capture({
+            distinctId: organizationId,
+            event: 'subscription_changed',
+            source: 'stripe-webhook',
+            properties: {
+              previousPlan,
+              newPlan,
+              isDowngrade,
+            },
+          });
+        } catch (capErr) {
+          logger.error('[billing.webhook] analytics capture subscription_changed failed (non-fatal)', {
+            organizationId,
+            error: capErr?.message ?? String(capErr),
+          });
+        }
+      }
+
       // Plan switch mid-cycle = refresh the active week snapshot to the new plan.
       // Unlike cron-driven resetWeek, this preserves meterUsed by default so a plan
       // change does not refund or double-charge already attributed usage.
diff --git a/modules/billing/tests/billing.webhook.subscription-changed-analytics.unit.tests.js b/modules/billing/tests/billing.webhook.subscription-changed-analytics.unit.tests.js
@@ -0,0 +1,259 @@
+/**
+ * Module dependencies.
+ */
+import { jest, describe, test, beforeEach, afterEach, expect } from '@jest/globals';
+
+/**
+ * Unit tests for subscription_changed analytics emit in billing.webhook.service.js
+ *   - captures when plan changes and AnalyticsService is configured
+ *   - no-op when AnalyticsService.isConfigured() returns false (no PostHog)
+ *   - no capture when plan did not change
+ */
+describe('billing.webhook.service — subscription_changed analytics emit:', () => {
+  let BillingWebhookService;
+  let mockAnalyticsCapture;
+  let mockAnalyticsIsConfigured;
+  let mockSubscriptionRepository;
+  let mockOrganizationRepository;
+  let mockResetService;
+  let mockEvents;
+  let mockStripe;
+
+  const orgId = '507f1f77bcf86cd799439011';
+  const subId = '607f1f77bcf86cd799439022';
+
+  const _mkStripeSubscription = (overrides = {}) => ({
+    id: 'sub_456',
+    status: 'active',
+    customer: 'cus_abc',
+    current_period_start: 1700000000,
+    current_period_end: 1700000000 + 2592000,
+    cancel_at_period_end: false,
+    items: {
+      data: [{
+        price: { id: 'price_growth', metadata: { planId: 'growth' } },
+        current_period_start: 1700000000,
+      }],
+    },
+    ...overrides,
+  });
+
+  const _mkEvent = (overrides = {}) => ({
+    id: 'evt_test_1',
+    type: 'customer.subscription.updated',
+    created: 1700000100,
+    data: { previous_attributes: {} },
+    ...overrides,
+  });
+
+  beforeEach(async () => {
+    jest.resetModules();
+
+    mockAnalyticsCapture = jest.fn();
+    mockAnalyticsIsConfigured = jest.fn().mockReturnValue(true);
+
+    mockSubscriptionRepository = {
+      findByStripeSubscriptionId: jest.fn().mockResolvedValue({
+        _id: subId,
+        organization: orgId,
+        plan: 'free',
+      }),
+      findByStripeCustomerId: jest.fn().mockResolvedValue(null),
+      create: jest.fn().mockResolvedValue({}),
+      updateIfEventNewer: jest.fn().mockResolvedValue({ _id: subId }),
+    };
+
+    mockOrganizationRepository = {
+      setPlan: jest.fn().mockResolvedValue({}),
+    };
+
+    mockResetService = {
+      resetWeek: jest.fn().mockResolvedValue({}),
+      forceRotateForPlanChange: jest.fn().mockResolvedValue({}),
+    };
+
+    mockEvents = { emit: jest.fn() };
+
+    mockStripe = {
+      subscriptions: { retrieve: jest.fn() },
+    };
+
+    jest.unstable_mockModule('../../../lib/services/analytics.js', () => ({
+      default: {
+        capture: mockAnalyticsCapture,
+        isConfigured: mockAnalyticsIsConfigured,
+      },
+    }));
+
+    jest.unstable_mockModule('../repositories/billing.subscription.repository.js', () => ({
+      default: mockSubscriptionRepository,
+    }));
+
+    jest.unstable_mockModule('../repositories/billing.processedStripeEvent.repository.js', () => ({
+      default: {
+        wasProcessed: jest.fn().mockResolvedValue(false),
+        tryRecord: jest.fn().mockResolvedValue({ recorded: true }),
+      },
+    }));
+
+    jest.unstable_mockModule('../../organizations/repositories/organizations.repository.js', () => ({
+      default: mockOrganizationRepository,
+    }));
+
+    jest.unstable_mockModule('../services/billing.extra.service.js', () => ({
+      default: { creditPack: jest.fn(), refundPartial: jest.fn() },
+    }));
+
+    jest.unstable_mockModule('../services/billing.reset.service.js', () => ({
+      default: mockResetService,
+    }));
+
+    jest.unstable_mockModule('../lib/stripe.js', () => ({
+      default: jest.fn(() => mockStripe),
+    }));
+
+    jest.unstable_mockModule('../lib/events.js', () => ({
+      default: mockEvents,
+    }));
+
+    jest.unstable_mockModule('../../../lib/services/logger.js', () => ({
+      default: { info: jest.fn(), error: jest.fn(), warn: jest.fn() },
+    }));
+
+    jest.unstable_mockModule('../../../config/index.js', () => ({
+      default: {
+        billing: {
+          plans: ['free', 'growth', 'pro'],
+          meterMode: true,
+        },
+      },
+    }));
+
+    jest.unstable_mockModule('mongoose', () => ({
+      default: {
+        Types: { ObjectId: { isValid: (id) => /^[a-f\d]{24}$/i.test(id) } },
+        model: () => ({}),
+      },
+    }));
+
+    const mod = await import('../services/billing.webhook.service.js');
+    BillingWebhookService = mod.default;
+  });
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  describe('when plan changes and AnalyticsService is configured', () => {
+    test('captures subscription_changed with previousPlan, newPlan, isDowngrade', async () => {
+      // existing sub has free plan, event carries growth plan → plan change
+      await BillingWebhookService.handleSubscriptionUpdated(
+        _mkStripeSubscription({
+          items: {
+            data: [{ price: { id: 'price_growth', metadata: { planId: 'growth' } }, current_period_start: 1700000000 }],
+          },
+        }),
+        _mkEvent({
+          data: {
+            previous_attributes: {
+              items: { data: [{ price: { id: 'price_free', metadata: { planId: 'free' } } }] },
+            },
+          },
+        }),
+      );
+
+      expect(mockAnalyticsIsConfigured).toHaveBeenCalled();
+      const subscriptionChangedCalls = mockAnalyticsCapture.mock.calls.filter(
+        ([arg]) => arg.event === 'subscription_changed',
+      );
+      expect(subscriptionChangedCalls).toHaveLength(1);
+      const [call] = subscriptionChangedCalls;
+      expect(call[0].distinctId).toBe(orgId);
+      expect(call[0].source).toBe('stripe-webhook');
+      expect(call[0].properties).toMatchObject({
+        previousPlan: 'free',
+        newPlan: 'growth',
+        isDowngrade: false,
+      });
+    });
+
+    test('marks isDowngrade=true when switching from higher to lower plan', async () => {
+      await BillingWebhookService.handleSubscriptionUpdated(
+        _mkStripeSubscription({
+          items: {
+            data: [{ price: { id: 'price_free', metadata: { planId: 'free' } }, current_period_start: 1700000000 }],
+          },
+        }),
+        _mkEvent({
+          data: {
+            previous_attributes: {
+              items: { data: [{ price: { id: 'price_pro', metadata: { planId: 'pro' } } }] },
+            },
+          },
+        }),
+      );
+
+      const subscriptionChangedCalls = mockAnalyticsCapture.mock.calls.filter(
+        ([arg]) => arg.event === 'subscription_changed',
+      );
+      expect(subscriptionChangedCalls).toHaveLength(1);
+      expect(subscriptionChangedCalls[0][0].properties.isDowngrade).toBe(true);
+    });
+  });
+
+  describe('when AnalyticsService is not configured (no PostHog)', () => {
+    test('does not capture subscription_changed (clean no-op)', async () => {
+      mockAnalyticsIsConfigured.mockReturnValue(false);
+
+      await BillingWebhookService.handleSubscriptionUpdated(
+        _mkStripeSubscription({
+          items: {
+            data: [{ price: { id: 'price_growth', metadata: { planId: 'growth' } }, current_period_start: 1700000000 }],
+          },
+        }),
+        _mkEvent({
+          data: {
+            previous_attributes: {
+              items: { data: [{ price: { id: 'price_free', metadata: { planId: 'free' } } }] },
+            },
+          },
+        }),
+      );
+
+      expect(mockAnalyticsCapture).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('when plan did not change', () => {
+    test('does not capture subscription_changed', async () => {
+      // No previous_attributes.items — no plan change detected
+      await BillingWebhookService.handleSubscriptionUpdated(
+        _mkStripeSubscription(),
+        _mkEvent({
+          data: { previous_attributes: {} },
+        }),
+      );
+
+      const subscriptionChangedCalls = mockAnalyticsCapture.mock.calls.filter(
+        ([arg]) => arg.event === 'subscription_changed',
+      );
+      expect(subscriptionChangedCalls).toHaveLength(0);
+    });
+  });
+
+  describe('when event is stale (updateIfEventNewer returns null)', () => {
+    test('does not capture subscription_changed', async () => {
+      mockSubscriptionRepository.updateIfEventNewer.mockResolvedValue(null);
+
+      await BillingWebhookService.handleSubscriptionUpdated(
+        _mkStripeSubscription(),
+        _mkEvent(),
+      );
+
+      const subscriptionChangedCalls = mockAnalyticsCapture.mock.calls.filter(
+        ([arg]) => arg.event === 'subscription_changed',
+      );
+      expect(subscriptionChangedCalls).toHaveLength(0);
+    });
+  });
+});
