[release/7.0] Fix making column required on SQL Server with idempotent migrations

src/EFCore.SqlServer/Migrations/SqlServerMigrationsSqlGenerator.cs

@@ -35,6 +35,9 @@ public class SqlServerMigrationsSqlGenerator : MigrationsSqlGenerator
 
  private readonly ICommandBatchPreparer _commandBatchPreparer;
 
+ private static readonly bool QuirkEnabled29619
+ = AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue29619", out var enabled) && enabled;
+
  /// <summary>
  /// Creates a new <see cref="SqlServerMigrationsSqlGenerator" /> instance.
  /// </summary>
@@ -369,17 +372,46 @@ protected override void Generate(
  defaultValueSql = typeMapping.GenerateSqlLiteral(operation.DefaultValue);
  }
 
- builder
- .Append("UPDATE ")
- .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Table, operation.Schema))
- .Append(" SET ")
- .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Name))
- .Append(" = ")
- .Append(defaultValueSql)
- .Append(" WHERE ")
- .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Name))
- .Append(" IS NULL")
- .AppendLine(Dependencies.SqlGenerationHelper.StatementTerminator);
+ if (QuirkEnabled29619)
+ {
+ builder
+ .Append("UPDATE ")
+ .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Table, operation.Schema))
+ .Append(" SET ")
+ .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Name))
+ .Append(" = ")
+ .Append(defaultValueSql)
+ .Append(" WHERE ")
+ .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Name))
+ .Append(" IS NULL");
+ }
+ else
+ {
+ var updateBuilder = new StringBuilder()
+ .Append("UPDATE ")
+ .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Table, operation.Schema))
+ .Append(" SET ")
+ .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Name))
+ .Append(" = ")
+ .Append(defaultValueSql)
+ .Append(" WHERE ")
+ .Append(Dependencies.SqlGenerationHelper.DelimitIdentifier(operation.Name))
+ .Append(" IS NULL");
+
+ if (Options.HasFlag(MigrationsSqlGenerationOptions.Idempotent))
+ {
+ builder
+ .Append("EXEC(N'")
+ .Append(updateBuilder.ToString().TrimEnd('\n', '\r', ';').Replace("'", "''"))
+ .Append("')");
+ }
+ else
+ {
+ builder.Append(updateBuilder.ToString());
+ }
+ }
+
+ builder.AppendLine(Dependencies.SqlGenerationHelper.StatementTerminator);
  }
 
  if (alterStatementNeeded)

test/EFCore.Relational.Specification.Tests/Migrations/MigrationsSqlGeneratorTestBase.cs

@@ -750,6 +750,9 @@ protected MigrationsSqlGeneratorTestBase(
  ContextOptions = options;
  }
 
+ protected virtual void Generate(MigrationOperation operation, MigrationsSqlGenerationOptions options)
+ => Generate(null, new[] { operation }, options);
+
  protected virtual void Generate(params MigrationOperation[] operation)
  => Generate(null, operation);
 

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

@@ -1180,6 +1180,41 @@ public virtual void CreateIndex_generates_exec_when_legacy_filter_and_idempotent
 """);
  }
 
+ [ConditionalFact]
+ public virtual void AlterColumn_make_required_with_idempotent()
+ {
+ Generate(
+ new AlterColumnOperation
+ {
+ Table = "Person",
+ Name = "Name",
+ ClrType = typeof(string),
+ IsNullable = false,
+ DefaultValue = "",
+ OldColumn = new AddColumnOperation
+ {
+ Table = "Person",
+ Name = "Name",
+ ClrType = typeof(string),
+ IsNullable = true
+ }
+ },
+ MigrationsSqlGenerationOptions.Idempotent);
+
+ AssertSql(
+"""
+DECLARE @var0 sysname;
+SELECT @var0 = [d].[name]
+FROM [sys].[default_constraints] [d]
+INNER JOIN [sys].[columns] [c] ON [d].[parent_column_id] = [c].[column_id] AND [d].[parent_object_id] = [c].[object_id]
+WHERE ([d].[parent_object_id] = OBJECT_ID(N'[Person]') AND [c].[name] = N'Name');
+IF @var0 IS NOT NULL EXEC(N'ALTER TABLE [Person] DROP CONSTRAINT [' + @var0 + '];');
+EXEC(N'UPDATE [Person] SET [Name] = N'''' WHERE [Name] IS NULL');
+ALTER TABLE [Person] ALTER COLUMN [Name] nvarchar(max) NOT NULL;
+ALTER TABLE [Person] ADD DEFAULT N'' FOR [Name];
+""");
+ }
+
  private static void CreateGotModel(ModelBuilder b)
  => b.HasDefaultSchema("dbo").Entity(
  "Person", pb =>