Throw if required primitive collection is null when saving changes (#31521)

Author: ajcvickers

src/EFCore/ChangeTracking/Internal/InternalEntityEntry.cs

@@ -1571,6 +1571,14 @@ public InternalEntityEntry PrepareToSave()
 
                     throw new InvalidOperationException(CoreStrings.UnknownKeyValue(entityType.DisplayName(), property.Name));
                 }
+
+                if (property.GetElementType() != null
+                    && !property.IsNullable
+                    && GetCurrentValue(property) == null)
+                {
+                    throw new InvalidOperationException(
+                        CoreStrings.NullRequiredPrimitiveCollection(EntityType.DisplayName(), property.Name));
+                }
             }
         }
         else if (EntityState == EntityState.Modified)

src/EFCore/Properties/CoreStrings.Designer.cs

@@ -1246,6 +1246,9 @@
   <data name="NullableKey" xml:space="preserve">
     <value>A key on entity type '{entityType}' cannot contain the property '{property}' because it is nullable/optional. All properties on which a key is declared must be marked as non-nullable/required.</value>
   </data>
+  <data name="NullRequiredPrimitiveCollection" xml:space="preserve">
+    <value>The primitive collection property '{type}.{property}' is configured as required (non-nullable) but has a null value when saving changes. Either mark the property as optional (nullable) or set a non-null value.</value>
+  </data>
   <data name="ObjectRemovedFromModel" xml:space="preserve">
     <value>The object has been removed from the model.</value>
   </data>

src/EFCore/Properties/CoreStrings.resx

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.ObjectModel;
+using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
 
 namespace Microsoft.EntityFrameworkCore.TestModels.JsonQuery;
@@ -73,7 +74,10 @@ public IList<bool> TestBooleanCollection
     }
 
     public byte[] TestByteCollection { get; set; }
+
+    [Required]
     public List<Guid> TestGuidCollection { get; set; }
+
     public IList<ushort> TestUnsignedInt16Collection { get; set; }
     public uint[] TestUnsignedInt32Collection { get; set; }
     public ObservableCollection<ulong> TestUnsignedInt64Collection { get; set; }

test/EFCore.Relational.Specification.Tests/TestModels/JsonQuery/JsonEntityAllTypes.cs

@@ -2971,6 +2971,21 @@ public virtual Task Edit_single_property_relational_collection_of_nullable_enum_
                 Assert.False(result.NewCollectionSet);
             });
 
+    [ConditionalFact]
+    public virtual async Task SaveChanges_throws_when_required_primitive_collection_is_null()
+        => await TestHelpers.ExecuteWithStrategyInTransactionAsync(
+            CreateContext,
+            UseTransaction,
+            async context =>
+            {
+                var entity = new JsonEntityAllTypes { TestGuidCollection = null };
+                context.Add(entity);
+
+                Assert.Equal(
+                    CoreStrings.NullRequiredPrimitiveCollection(nameof(JsonEntityAllTypes), nameof(JsonEntityAllTypes.TestGuidCollection)),
+                    (await Assert.ThrowsAsync<InvalidOperationException>(async () => await context.SaveChangesAsync())).Message);
+            });
+
     public void UseTransaction(DatabaseFacade facade, IDbContextTransaction transaction)
         => facade.UseTransaction(transaction.GetDbTransaction());