[web] Redirect to plans page when previewing subscription change without an existing subscription (#33925)

GitOrigin-RevId: feb47fb519dd7872149d787a8543293cae66a908

services/web/app/src/Features/Subscription/SubscriptionController.mjs

@@ -885,11 +885,22 @@ async function previewSubscription(req, res, next) {
     }
   }
 
-  const subscriptionChange =
-    await SubscriptionHandler.promises.previewSubscriptionChange(
-      userId,
-      planCode
-    )
+  let subscriptionChange
+  try {
+    subscriptionChange =
+      await SubscriptionHandler.promises.previewSubscriptionChange(
+        userId,
+        planCode
+      )
+  } catch (err) {
+    if (
+      err instanceof Error &&
+      err.constructor.name === 'PaymentServiceResourceNotFoundError'
+    ) {
+      return res.redirect('/user/subscription/plans')
+    }
+    throw err
+  }
   /** @type {PaymentMethod[]} */
   const paymentMethod = await Modules.promises.hooks.fire(
     'getPaymentMethod',

services/web/test/unit/src/Subscription/SubscriptionController.test.mjs

@@ -3,6 +3,7 @@ import sinon from 'sinon'
 import MockRequest from '../helpers/MockRequest.mjs'
 import MockResponse from '../helpers/MockResponse.mjs'
 import SubscriptionErrors from '../../../../app/src/Features/Subscription/Errors.mjs'
+import { PaymentServiceResourceNotFoundError } from '../../../../modules/subscriptions/app/src/PaymentServiceErrors.mjs'
 import SubscriptionHelper from '../../../../app/src/Features/Subscription/SubscriptionHelper.mjs'
 import { AI_ADD_ON_CODE } from '../../../../app/src/Features/Subscription/AiHelper.mjs'
 
@@ -1772,6 +1773,20 @@ describe('SubscriptionController', function () {
       expect(ctx.res.render).not.to.have.been.called
     })
 
+    it('redirects to the plans page when the user has no subscription to preview', async function (ctx) {
+      ctx.SubscriptionHandler.promises.previewSubscriptionChange = sinon
+        .stub()
+        .rejects(new PaymentServiceResourceNotFoundError('no subscription'))
+      ctx.res.redirect = sinon.stub()
+
+      await ctx.SubscriptionController.previewSubscription(ctx.req, ctx.res)
+
+      expect(ctx.res.redirect).to.have.been.calledWith(
+        '/user/subscription/plans'
+      )
+      expect(ctx.res.render).not.to.have.been.called
+    })
+
     it('passes trialDisabledReason to the view when the user is ineligible for a free trial', async function (ctx) {
       ctx.req.query = { planCode: 'collaborator_free_trial_7_days' }
       ctx.PlansLocator.findLocalPlanInSettings.returns({