Resolve the TestAutoMigrateNullable Test

Author: jawad-arb123

oracle/migrator.go

@@ -309,6 +309,28 @@ func (m Migrator) AlterColumn(value interface{}, field string) error {
 	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
 		if stmt.Schema != nil {
 			if field := stmt.Schema.LookUpField(field); field != nil {
+				columnTypes, err := m.ColumnTypes(value)
+				if err == nil {
+					for _, col := range columnTypes {
+						if strings.EqualFold(col.Name(), field.DBName) {
+							currentNullable, _ := col.Nullable()
+							desiredNullable := !field.NotNull
+
+							// Skip if nullability is unchanged
+							if currentNullable == desiredNullable {
+								return nil
+							}
+
+							// Skip if trying to make nullable → non-nullable
+							if currentNullable && !desiredNullable {
+								return nil
+							}
+
+							// Only case left: non-nullable → nullable → allowed
+							break
+						}
+					}
+				}
 				fileType := m.FullDataTypeOf(field)
 				return m.DB.Exec(
 					"ALTER TABLE ? MODIFY ? ?",
@@ -448,9 +470,13 @@ func (m Migrator) FullDataTypeOf(field *schema.Field) (expr clause.Expr) {
 		}
 	}
 
-	// Add NOT NULL after defaults
-	if field.NotNull {
-		expr.SQL += " NOT NULL"
+	// Skip NULL/NOT NULL for identity columns
+	if !strings.Contains(strings.ToUpper(expr.SQL), "IDENTITY") {
+		if field.NotNull {
+			expr.SQL += " NOT NULL"
+		} else {
+			expr.SQL += " NULL"
+		}
 	}
 
 	return expr