Include schedule Phase 2 discount in premium tax estimate preview (#7385)

When a subscription has an active schedule during the ~15-day window before
renewal, the invoice preview for tax estimation was built with the new price
but without the Phase 2 discount coupon. This caused the estimated tax on the
subscription page to be higher than what Stripe would actually charge.

Pass the coupon ID from the schedule's Phase 2 discount through to
EstimatePremiumTaxAsync so it is included in the InvoiceCreatePreviewOptions.

src/Core/Billing/Subscriptions/Queries/GetBitwardenSubscriptionQuery.cs

@@ -109,9 +109,9 @@ public class GetBitwardenSubscriptionQuery(
 
         var (cartLevelDiscount, productLevelDiscounts) = GetStripeDiscounts(subscription);
 
-        var scheduleDiscount = cartLevelDiscount == null
+        var (scheduleDiscount, scheduleCouponId) = cartLevelDiscount == null
             ? await GetSchedulePhase2DiscountAsync(subscription)
-            : null;
+            : (null, (string?)null);
 
         var availablePlan = plans.First(plan => plan.Available);
         var onCurrentPricing = passwordManagerSeatsItem.Price.Id == availablePlan.Seat.StripePriceId;
@@ -127,7 +127,7 @@ public class GetBitwardenSubscriptionQuery(
         else
         {
             seatCost = availablePlan.Seat.Price;
-            estimatedTax = await EstimatePremiumTaxAsync(subscription, plans, availablePlan);
+            estimatedTax = await EstimatePremiumTaxAsync(subscription, plans, availablePlan, scheduleCouponId);
         }
 
         var passwordManagerSeats = new CartItem
@@ -166,7 +166,8 @@ public class GetBitwardenSubscriptionQuery(
     private async Task<decimal> EstimatePremiumTaxAsync(
         Subscription subscription,
         List<PremiumPlan>? plans = null,
-        PremiumPlan? availablePlan = null)
+        PremiumPlan? availablePlan = null,
+        string? couponId = null)
     {
         try
         {
@@ -195,6 +196,11 @@ public class GetBitwardenSubscriptionQuery(
                         };
                     }).ToList()
                 };
+
+                if (couponId != null)
+                {
+                    options.Discounts = [new InvoiceDiscountOptions { Coupon = couponId }];
+                }
             }
             else
             {
@@ -248,11 +254,11 @@ public class GetBitwardenSubscriptionQuery(
         return (cartLevel.FirstOrDefault(), productLevel);
     }
 
-    private async Task<BitwardenDiscount?> GetSchedulePhase2DiscountAsync(Subscription subscription)
+    private async Task<(BitwardenDiscount? Discount, string? CouponId)> GetSchedulePhase2DiscountAsync(Subscription subscription)
     {
         if (string.IsNullOrEmpty(subscription.ScheduleId))
         {
-            return null;
+            return (null, null);
         }
 
         try
@@ -265,17 +271,18 @@ public class GetBitwardenSubscriptionQuery(
 
             if (schedule.Status != SubscriptionScheduleStatus.Active || schedule.Phases.Count < 2)
             {
-                return null;
+                return (null, null);
             }
 
-            return schedule.Phases[1].Discounts?.FirstOrDefault()?.Coupon;
+            var discount = schedule.Phases[1].Discounts?.FirstOrDefault();
+            return (discount?.Coupon, discount?.CouponId);
         }
         catch (StripeException stripeException)
         {
             logger.LogError(stripeException,
                 "Failed to retrieve subscription schedule ({ScheduleID}) for discount resolution",
                 subscription.ScheduleId);
-            return null;
+            return (null, null);
         }
     }
 

test/Core.Test/Billing/Subscriptions/Queries/GetBitwardenSubscriptionQueryTests.cs

@@ -751,6 +751,86 @@ public class GetBitwardenSubscriptionQueryTests
         Assert.Null(result.Cart.PasswordManager.Seats.Discount);
     }
 
+    [Fact]
+    public async Task Run_UserOnLegacyPricing_WithScheduleDiscount_IncludesCouponInTaxPreview()
+    {
+        var user = CreateUser();
+        var subscription = CreateSubscription(SubscriptionStatus.Active, legacyPricing: true);
+        subscription.ScheduleId = "sub_sched_test";
+        var premiumPlans = CreatePremiumPlans();
+        var schedule = CreateSubscriptionSchedule(percentOff: 30, couponId: "milestone-2c");
+
+        _stripeAdapter.GetSubscriptionAsync(user.GatewaySubscriptionId, Arg.Any<SubscriptionGetOptions>())
+            .Returns(subscription);
+        _pricingClient.ListPremiumPlans().Returns(premiumPlans);
+        _stripeAdapter.CreateInvoicePreviewAsync(Arg.Any<InvoiceCreatePreviewOptions>())
+            .Returns(CreateInvoicePreview(totalTax: 150));
+        _stripeAdapter.GetSubscriptionScheduleAsync("sub_sched_test", Arg.Any<SubscriptionScheduleGetOptions>())
+            .Returns(schedule);
+
+        await _query.Run(user);
+
+        await _stripeAdapter.Received(1).CreateInvoicePreviewAsync(
+            Arg.Is<InvoiceCreatePreviewOptions>(opts =>
+                opts.Subscription == null &&
+                opts.SubscriptionDetails != null &&
+                opts.Discounts != null &&
+                opts.Discounts.Count == 1 &&
+                opts.Discounts[0].Coupon == "milestone-2c"));
+    }
+
+    [Fact]
+    public async Task Run_UserOnLegacyPricing_WithScheduleNoDiscount_DoesNotIncludeCouponInTaxPreview()
+    {
+        var user = CreateUser();
+        var subscription = CreateSubscription(SubscriptionStatus.Active, legacyPricing: true);
+        subscription.ScheduleId = "sub_sched_test";
+        var premiumPlans = CreatePremiumPlans();
+        var schedule = CreateSubscriptionSchedule(includePhase2: false);
+
+        _stripeAdapter.GetSubscriptionAsync(user.GatewaySubscriptionId, Arg.Any<SubscriptionGetOptions>())
+            .Returns(subscription);
+        _pricingClient.ListPremiumPlans().Returns(premiumPlans);
+        _stripeAdapter.CreateInvoicePreviewAsync(Arg.Any<InvoiceCreatePreviewOptions>())
+            .Returns(CreateInvoicePreview());
+        _stripeAdapter.GetSubscriptionScheduleAsync("sub_sched_test", Arg.Any<SubscriptionScheduleGetOptions>())
+            .Returns(schedule);
+
+        await _query.Run(user);
+
+        await _stripeAdapter.Received(1).CreateInvoicePreviewAsync(
+            Arg.Is<InvoiceCreatePreviewOptions>(opts =>
+                opts.Subscription == null &&
+                opts.SubscriptionDetails != null &&
+                opts.Discounts == null));
+    }
+
+    [Fact]
+    public async Task Run_UserOnLegacyPricing_WithSchedulePhase2NoDiscount_DoesNotIncludeCouponInTaxPreview()
+    {
+        var user = CreateUser();
+        var subscription = CreateSubscription(SubscriptionStatus.Active, legacyPricing: true);
+        subscription.ScheduleId = "sub_sched_test";
+        var premiumPlans = CreatePremiumPlans();
+        var schedule = CreateSubscriptionSchedule();
+
+        _stripeAdapter.GetSubscriptionAsync(user.GatewaySubscriptionId, Arg.Any<SubscriptionGetOptions>())
+            .Returns(subscription);
+        _pricingClient.ListPremiumPlans().Returns(premiumPlans);
+        _stripeAdapter.CreateInvoicePreviewAsync(Arg.Any<InvoiceCreatePreviewOptions>())
+            .Returns(CreateInvoicePreview());
+        _stripeAdapter.GetSubscriptionScheduleAsync("sub_sched_test", Arg.Any<SubscriptionScheduleGetOptions>())
+            .Returns(schedule);
+
+        await _query.Run(user);
+
+        await _stripeAdapter.Received(1).CreateInvoicePreviewAsync(
+            Arg.Is<InvoiceCreatePreviewOptions>(opts =>
+                opts.Subscription == null &&
+                opts.SubscriptionDetails != null &&
+                opts.Discounts == null));
+    }
+
     #region Helper Methods
 
     private static User CreateUser()
@@ -903,7 +983,8 @@ public class GetBitwardenSubscriptionQueryTests
         decimal? percentOff = null,
         long? amountOff = null,
         string status = StripeConstants.SubscriptionScheduleStatus.Active,
-        bool validCoupon = true)
+        bool validCoupon = true,
+        string? couponId = null)
     {
         var phases = new List<SubscriptionSchedulePhase>
         {
@@ -912,13 +993,18 @@ public class GetBitwardenSubscriptionQueryTests
 
         if (includePhase2)
         {
-            phases.Add(new SubscriptionSchedulePhase
-            {
-                Discounts = [new SubscriptionSchedulePhaseDiscount
+            var discounts = percentOff != null || amountOff != null
+                ? new List<SubscriptionSchedulePhaseDiscount>
                 {
-                    Coupon = new Coupon { Valid = validCoupon, PercentOff = percentOff, AmountOff = amountOff }
-                }]
-            });
+                    new()
+                    {
+                        CouponId = couponId,
+                        Coupon = new Coupon { Id = couponId, Valid = validCoupon, PercentOff = percentOff, AmountOff = amountOff }
+                    }
+                }
+                : new List<SubscriptionSchedulePhaseDiscount>();
+
+            phases.Add(new SubscriptionSchedulePhase { Discounts = discounts });
         }
 
         return new SubscriptionSchedule