Fix computed column nullability mismatch in temporal table migrations

src/EFCore.SqlServer/Migrations/SqlServerMigrationsSqlGenerator.cs

@@ -3004,6 +3004,21 @@ alterTableOperation.OldTable[SqlServerAnnotationNames.TemporalHistoryTableSchema
                                 // as long as their names and types (including nullability) match
                                 // so we remove ComputedColumnSql info, so that the column in history table "appears normal"
                                 addHistoryTableColumnOperation.ComputedColumnSql = null;
+
+                                // For computed columns, ensure the history table column has the same nullability
+                                // as the computed column in the main table. For persisted computed columns,
+                                // SQL Server typically treats them as non-nullable if the computation is non-nullable.
+                                // We ensure consistency by making the history table column non-nullable and providing a default value.
+                                addHistoryTableColumnOperation.IsNullable = false;
+                                if (addHistoryTableColumnOperation.DefaultValue == null && addHistoryTableColumnOperation.DefaultValueSql == null)
+                                {
+                                    // Provide a default value that matches the computed column type
+                                    addHistoryTableColumnOperation.DefaultValue = addColumnOperation.ClrType == typeof(int) || addColumnOperation.ClrType == typeof(int?) 
+                                        ? 0 
+                                        : addColumnOperation.ClrType.IsValueType 
+                                            ? Activator.CreateInstance(addColumnOperation.ClrType) 
+                                            : null;
+                                }
                             }
 
                             operations.Add(addHistoryTableColumnOperation);
@@ -3226,6 +3241,8 @@ static TemporalOperationInformation BuildTemporalInformationFromMigrationOperati
             };
         }
 
+
+
         void DisableVersioning(
             string tableName,
             string? schema,

test/EFCore.SqlServer.FunctionalTests/Migrations/MigrationsSqlServerTest.TemporalTables.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Text.RegularExpressions;
 using Microsoft.EntityFrameworkCore.SqlServer.Internal;
 using Microsoft.EntityFrameworkCore.SqlServer.Metadata.Internal;
 

test/EFCore.SqlServer.FunctionalTests/Migrations/SqlServerMigrationsSqlGeneratorTest.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Text.RegularExpressions;
 using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.SqlServer.Internal;
 using Microsoft.EntityFrameworkCore.SqlServer.Metadata.Internal;