From edc07042d81aa44e552feb3460755a96d0a1c66f Mon Sep 17 00:00:00 2001
From: Usman Khan <kha333n@gmail.com>
Date: Mon, 24 Aug 2026 19:20:05 +0500
Subject: [PATCH] Honour discount conditions in BuyXGetY
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AbstractDiscountType::checkDiscountConditions() enforces a discount's minimum
spend, customer restrictions and per-user usage limit. AmountOff::apply() guards
on it before doing anything; BuyXGetY::apply() never calls it, so a BuyXGetY
discount applies whenever its quantity condition is met, whatever those fields
say.

Dates, max_uses, the coupon and the channel are already enforced by the query in
DiscountManager::getDiscounts(), so those continue to hold. What is only checked
in checkDiscountConditions() is ignored: a "spend £50, get one free" promotion
fires on a £20 cart, and a discount restricted to named customers applies to
everyone.

Adds the same guard AmountOff uses.

Tests cover a cart below the advertised minimum spend and a discount restricted
to a customer the cart does not belong to; both fail on 1.x with
"Failed asserting that 1000 matches expected 0". A third asserts the discount
still applies when the minimum is met, so the guard is not simply switching it
off.

Core suite: 556 passing before, 559 after.
---
 packages/core/src/DiscountTypes/BuyXGetY.php  |   4 +
 .../DiscountTypes/BuyXGetYConditionsTest.php  | 136 ++++++++++++++++++
 2 files changed, 140 insertions(+)
 create mode 100644 tests/core/Unit/DiscountTypes/BuyXGetYConditionsTest.php

diff --git a/packages/core/src/DiscountTypes/BuyXGetY.php b/packages/core/src/DiscountTypes/BuyXGetY.php
index 32ceb017cd..968b8290ba 100644
--- a/packages/core/src/DiscountTypes/BuyXGetY.php
+++ b/packages/core/src/DiscountTypes/BuyXGetY.php
@@ -51,6 +51,10 @@ public function getRewardQuantity($linesQuantity, $minQty, $rewardQty, $maxRewar
      */
     public function apply(CartContract $cart): CartContract
     {
+        if (! $this->checkDiscountConditions($cart)) {
+            return $cart;
+        }
+
         $data = $this->discount->data;
 
         $minQty = $data['min_qty'] ?? null;
diff --git a/tests/core/Unit/DiscountTypes/BuyXGetYConditionsTest.php b/tests/core/Unit/DiscountTypes/BuyXGetYConditionsTest.php
new file mode 100644
index 0000000000..8454b2354d
--- /dev/null
+++ b/tests/core/Unit/DiscountTypes/BuyXGetYConditionsTest.php
@@ -0,0 +1,136 @@
+<?php
+
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Lunar\DiscountTypes\BuyXGetY;
+use Lunar\Models\Cart;
+use Lunar\Models\Channel;
+use Lunar\Models\Currency;
+use Lunar\Models\Customer;
+use Lunar\Models\CustomerGroup;
+use Lunar\Models\Discount;
+use Lunar\Models\Price;
+use Lunar\Models\Product;
+use Lunar\Models\ProductVariant;
+use Lunar\Tests\Core\TestCase;
+
+uses(TestCase::class);
+
+uses(RefreshDatabase::class);
+
+/**
+ * `AmountOff::apply()` guards on `checkDiscountConditions()`; `BuyXGetY::apply()`
+ * does not, so it applies whenever the quantity condition is met.
+ *
+ * Dates, `max_uses`, the coupon and the channel are already enforced by the
+ * query in `DiscountManager::getDiscounts()`, so those still hold. What is only
+ * checked in `checkDiscountConditions()` — the minimum spend, customer
+ * restrictions and `max_uses_per_user` — is ignored entirely.
+ */
+function buyXGetYConditionCart(array $discountData, array $discountAttributes = []): Cart
+{
+    $customerGroup = CustomerGroup::factory()->create(['default' => true]);
+    $channel = Channel::factory()->create(['default' => true]);
+    $currency = Currency::factory()->create(['code' => 'GBP', 'default' => true]);
+
+    $conditionProduct = Product::factory()->create();
+    $rewardProduct = Product::factory()->create();
+
+    $condition = ProductVariant::factory()->create(['product_id' => $conditionProduct->id]);
+    $reward = ProductVariant::factory()->create(['product_id' => $rewardProduct->id]);
+
+    foreach ([$condition, $reward] as $variant) {
+        Price::factory()->create([
+            'price' => 1000, // £10
+            'min_quantity' => 1,
+            'currency_id' => $currency->id,
+            'priceable_type' => $variant->getMorphClass(),
+            'priceable_id' => $variant->id,
+        ]);
+    }
+
+    $discount = Discount::factory()->create(array_merge([
+        'type' => BuyXGetY::class,
+        'name' => 'Buy one get one',
+        'starts_at' => now()->subDay(),
+        'data' => array_merge([
+            'min_qty' => 1,
+            'reward_qty' => 1,
+            'automatically_add_rewards' => false,
+        ], $discountData),
+    ], $discountAttributes));
+
+    $discount->channels()->attach([
+        $channel->id => ['enabled' => true, 'starts_at' => now()->subDay()],
+    ]);
+
+    $discount->customerGroups()->attach([
+        $customerGroup->id => ['enabled' => true, 'starts_at' => now()->subDay()],
+    ]);
+
+    $discount->discountables()->create([
+        'discountable_type' => $conditionProduct->getMorphClass(),
+        'discountable_id' => $conditionProduct->id,
+        'type' => 'condition',
+    ]);
+
+    $discount->discountables()->create([
+        'discountable_type' => $rewardProduct->getMorphClass(),
+        'discountable_id' => $rewardProduct->id,
+        'type' => 'reward',
+    ]);
+
+    $cart = Cart::factory()->create([
+        'channel_id' => $channel->id,
+        'currency_id' => $currency->id,
+        'coupon_code' => null,
+    ]);
+
+    // £10 of the condition product and £10 of the reward product: £20 total.
+    $cart->lines()->create([
+        'purchasable_type' => $condition->getMorphClass(),
+        'purchasable_id' => $condition->id,
+        'quantity' => 1,
+    ]);
+
+    $cart->lines()->create([
+        'purchasable_type' => $reward->getMorphClass(),
+        'purchasable_id' => $reward->id,
+        'quantity' => 1,
+    ]);
+
+    return $cart->refresh();
+}
+
+test('is not applied when the cart is below the minimum spend', function () {
+    // £50 minimum against a £20 cart.
+    $cart = buyXGetYConditionCart([
+        'min_prices' => ['GBP' => 5000],
+    ]);
+
+    $cart->calculate();
+
+    expect($cart->discountTotal->value)->toEqual(0);
+});
+
+test('is applied when the cart meets the minimum spend', function () {
+    // £10 minimum against a £20 cart.
+    $cart = buyXGetYConditionCart([
+        'min_prices' => ['GBP' => 1000],
+    ]);
+
+    $cart->calculate();
+
+    expect($cart->discountTotal->value)->toBeGreaterThan(0);
+});
+
+test('is not applied when the cart customer is not on the discount', function () {
+    $cart = buyXGetYConditionCart([]);
+
+    // Restrict the discount to a customer this cart does not belong to.
+    $discount = Discount::first();
+    $discount->customers()->attach(Customer::factory()->create()->id);
+
+    $cart->refresh()->calculate();
+
+    expect($cart->discountTotal->value)->toEqual(0);
+});