OCC-173: Discount is not applied if there is also another not discounted product in the shopping cart

.github/actions/spelling/allow/occ.txt

@@ -26,5 +26,6 @@ pricefield
 roadmap
 skus
 testproduct
+testdiscountedproduct
 unpublish
 webhooks

src/Modules/OrchardCore.Commerce/Recipes/OrchardCore.Commerce.Samples.Product.recipe.json

@@ -197,6 +197,89 @@
             "ProductSku": "TESTFREEPRODUCT"
           },
           "Product": {}
+        },
+        {
+          "ContentItemId": "testdiscountedproduct000",
+          "ContentItemVersionId": "[js:uuid()]",
+          "ContentType": "Product",
+          "DisplayText": "TestDiscountedProduct",
+          "Latest": true,
+          "Published": true,
+          "ModifiedUtc": "2022-08-10T19:34:57.2678948Z",
+          "PublishedUtc": "2022-08-10T19:34:57.2716912Z",
+          "CreatedUtc": "2022-08-10T19:34:57.2678948Z",
+          "Owner": "48a8p8cbg3ksqvyd14d75x9a59",
+          "Author": "admin",
+          "TitlePart": {
+            "Title": "TestDiscountedProduct"
+          },
+          "AutoroutePart": {
+            "Path": "testdiscountedproduct",
+            "SetHomepage": false,
+            "Disabled": false,
+            "RouteContainedItems": false,
+            "Absolute": false
+          },
+          "HtmlBodyPart": {
+            "Html": ""
+          },
+          "ProductPart": {
+            "Sku": "TESTDISCOUNTEDPRODUCT"
+          },
+          "PricePart": {
+            "Price": {
+              "value": 5.0,
+              "currency": "USD"
+            }
+          },
+          "InventoryPart": {
+            "Inventory": {
+              "TESTDISCOUNTEDPRODUCT": 5
+            },
+            "InventoryKeys": [
+              "TESTDISCOUNTEDPRODUCT"
+            ],
+            "AllowsBackOrder": {
+              "Value": true
+            },
+            "IgnoreInventory": {
+              "Value": false
+            },
+            "MaximumOrderQuantity": {
+              "Value": 2.0
+            },
+            "MinimumOrderQuantity": {
+              "Value": 1.0
+            },
+            "OutOfStockMessage": {
+              "Html": "A professional out of stock message."
+            },
+            "ProductSku": "TESTDISCOUNTEDPRODUCT"
+          },
+          "DiscountPart": {
+            "DiscountPercentage": {
+              "Value": null
+            },
+            "DiscountAmount": {
+              "Amount": {
+                "value": 2.0,
+                "currency": "USD"
+              }
+            },
+            "BeginningUtc": {
+              "Value": null
+            },
+            "ExpirationUtc": {
+              "Value": null
+            },
+            "MaximumProducts": {
+              "Value": null
+            },
+            "MinimumProducts": {
+              "Value": null
+            }
+          },
+          "Product": {}
         }
       ]
     }

src/Modules/OrchardCore.Commerce/Services/DiscountProvider.cs

@@ -24,7 +24,7 @@ public Task<bool> IsApplicableAsync(PromotionAndTaxProviderContext model) =>
     private static bool IsApplicable(
         IList<PromotionAndTaxProviderContextLineItem> lineItems,
         DateTime? purchaseDateTime) =>
-        lineItems.All(item => IsApplicablePerItem(item, purchaseDateTime));
+        lineItems.Any(item => IsApplicablePerItem(item, purchaseDateTime));
 
     private static bool IsApplicablePerItem(PromotionAndTaxProviderContextLineItem item, DateTime? purchaseDateTime)
     {

test/OrchardCore.Commerce.Tests.UI/Tests/PromotionTests/PromotionBehaviourTests.cs

@@ -3,6 +3,7 @@
 using Lombiq.Tests.UI.Extensions;
 using Lombiq.Tests.UI.Services;
 using OpenQA.Selenium;
+using Shouldly;
 using Xunit;
 using Xunit.Abstractions;
 using static OrchardCore.Commerce.Tests.UI.Constants.ContentItemIds;
@@ -35,4 +36,33 @@ async Task CheckDiscountPresenceAsync(bool hasNewPrice)
                 await CheckDiscountPresenceAsync(hasNewPrice: true);
             },
             browser);
+
+    [Theory, Chrome]
+    public Task DiscountShouldProperlyAppearOnDiscountedProduct(Browser browser) =>
+        ExecuteTestAfterSetupAsync(
+            async context =>
+            {
+                // Discount should appear on discounted product's page.
+                await context.GoToRelativeUrlAsync("/testdiscountedproduct");
+                context.Get(By.CssSelector(".price-part-price-field-value > del")).Text.ShouldBe("$5.00");
+                context.Get(By.CssSelector(".price-part-price-field-value > span")).Text.ShouldBe("$3.00");
+                await context.ClickReliablyOnSubmitAsync();
+
+                // Discount should appear in cart when discounted product is the only item in the cart.
+                context.Get(By.CssSelector(".shopping-cart-table-unit-price")).Text.ShouldBe("$3.00");
+
+                // Discount should appear in cart when discounted product is not the only item in the cart.
+                await context.GoToRelativeUrlAsync("/testproduct");
+                await context.ClickReliablyOnSubmitAsync();
+                context.Get(By.CssSelector(".shopping-cart-table-unit-price")).Text.ShouldBe("$3.00");
+
+                // Total should reflect discount as well.
+                context.Get(By.CssSelector(".shopping-cart-table-totals > div")).Text.ShouldBe("$8.00");
+
+                // Discount should still appear on discounted product's page when the cart contains a full-price item.
+                await context.GoToRelativeUrlAsync("/testdiscountedproduct");
+                context.Get(By.CssSelector(".price-part-price-field-value > del")).Text.ShouldBe("$5.00");
+                context.Get(By.CssSelector(".price-part-price-field-value > span")).Text.ShouldBe("$3.00");
+            },
+            browser);
 }