fix: migrator force modification of fields with no default value (#134)

* fix: migrator force modification of fields with no default value

* test: re-migrate table fields with or without default value

migrator.go

@@ -256,8 +256,6 @@ func (m Migrator) ColumnTypes(value interface{}) ([]gorm.ColumnType, error) {
 						column.DefaultValueValue.String = matches[1]
 						matches = defaultValueTrimRegexp.FindStringSubmatch(column.DefaultValueValue.String)
 					}
-				} else {
-					column.DefaultValueValue.Valid = true
 				}
 
 				for _, c := range rawColumnTypes {

migrator_test.go

@@ -2,7 +2,9 @@ package sqlserver_test
 
 import (
 	"os"
+	"reflect"
 	"testing"
+	"time"
 
 	"gorm.io/driver/sqlserver"
 	"gorm.io/gorm"
@@ -115,3 +117,74 @@ func TestCreateIndex(t *testing.T) {
 		t.Error("couldn't drop table testtable", tx.Error)
 	}
 }
+
+type TestTableDefaultValue struct {
+	ID        string     `gorm:"column:id;primaryKey"`
+	Name      string     `gorm:"column:name"`
+	Age       uint       `gorm:"column:age"`
+	Birthday  *time.Time `gorm:"column:birthday"`
+	CompanyID *int       `gorm:"column:company_id;default:0"`
+	ManagerID *uint      `gorm:"column:manager_id;default:0"`
+	Active    bool       `gorm:"column:active;default:1"`
+}
+
+func (*TestTableDefaultValue) TableName() string { return "test_table_default_value" }
+
+func TestReMigrateTableFieldsWithoutDefaultValue(t *testing.T) {
+	db, err := gorm.Open(sqlserver.Open(sqlserverDSN))
+	if err != nil {
+		t.Error(err)
+	}
+
+	var (
+		migrator             = db.Migrator()
+		tableModel           = new(TestTableDefaultValue)
+		fieldsWithDefault    = []string{"company_id", "manager_id", "active"}
+		fieldsWithoutDefault = []string{"id", "name", "age", "birthday"}
+
+		columnsWithDefault    []string
+		columnsWithoutDefault []string
+	)
+
+	defer func() {
+		if err = migrator.DropTable(tableModel); err != nil {
+			t.Errorf("couldn't drop table %q, got error: %v", tableModel.TableName(), err)
+		}
+	}()
+	if !migrator.HasTable(tableModel) {
+		if err = migrator.AutoMigrate(tableModel); err != nil {
+			t.Errorf("couldn't auto migrate table %q, got error: %v", tableModel.TableName(), err)
+		}
+	}
+	// If in the `Migrator.ColumnTypes` method `column.DefaultValueValue.Valid = true`,
+	// re-migrate the table will alter all fields without default value except for the primary key.
+	if err = db.Debug().Migrator().AutoMigrate(tableModel); err != nil {
+		t.Errorf("couldn't re-migrate table %q, got error: %v", tableModel.TableName(), err)
+	}
+
+	columnsWithDefault, columnsWithoutDefault, err = testGetMigrateColumns(db, tableModel)
+	if !reflect.DeepEqual(columnsWithDefault, fieldsWithDefault) {
+		// If in the `Migrator.ColumnTypes` method `column.DefaultValueValue.Valid = true`,
+		// fields with default value will include all fields: `[id name age birthday company_id manager_id active]`.
+		t.Errorf("expected columns with default value %v, got %v", fieldsWithDefault, columnsWithDefault)
+	}
+	if !reflect.DeepEqual(columnsWithoutDefault, fieldsWithoutDefault) {
+		t.Errorf("expected columns without default value %v, got %v", fieldsWithoutDefault, columnsWithoutDefault)
+	}
+}
+
+func testGetMigrateColumns(db *gorm.DB, dst interface{}) (columnsWithDefault, columnsWithoutDefault []string, err error) {
+	migrator := db.Migrator()
+	var columnTypes []gorm.ColumnType
+	if columnTypes, err = migrator.ColumnTypes(dst); err != nil {
+		return
+	}
+	for _, columnType := range columnTypes {
+		if _, ok := columnType.DefaultValue(); ok {
+			columnsWithDefault = append(columnsWithDefault, columnType.Name())
+		} else {
+			columnsWithoutDefault = append(columnsWithoutDefault, columnType.Name())
+		}
+	}
+	return
+}