[#6372] Fixed nullable constraint bug for columns during auto migration

migrator/migrator.go

@@ -524,8 +524,8 @@ func (m Migrator) MigrateColumn(value interface{}, field *schema.Field, columnTy
 
 	// check nullable
 	if nullable, ok := columnType.Nullable(); ok && nullable == field.NotNull {
-		// not primary key & database is nullable
-		if !field.PrimaryKey && nullable {
+		// not primary key & current database is non-nullable(to be nullable)
+		if !field.PrimaryKey && !nullable {
 			alterColumn = true
 		}
 	}

tests/migrate_test.go

@@ -148,6 +148,8 @@ func TestSmartMigrateColumn(t *testing.T) {
 		ID       uint
 		Name     string
 		Salary   float64
+		Bonus    float64 `gorm:"not null"`
+		Stock    float64
 		Birthday time.Time `gorm:"precision:4"`
 	}
 
@@ -157,8 +159,10 @@ func TestSmartMigrateColumn(t *testing.T) {
 
 	type UserMigrateColumn2 struct {
 		ID                  uint
-		Name                string    `gorm:"size:128"`
-		Salary              float64   `gorm:"precision:2"`
+		Name                string  `gorm:"size:128"`
+		Salary              float64 `gorm:"precision:2"`
+		Bonus               float64
+		Stock               float64   `gorm:"not null"`
 		Birthday            time.Time `gorm:"precision:2"`
 		NameIgnoreMigration string    `gorm:"size:100"`
 	}
@@ -182,6 +186,16 @@ func TestSmartMigrateColumn(t *testing.T) {
 			if precision, o, _ := columnType.DecimalSize(); (fullSupported || precision != 0) && precision != 2 {
 				t.Fatalf("salary's precision should be 2, but got %v %v", precision, o)
 			}
+		case "bonus":
+			// allow to change non-nullable to nullable
+			if nullable, _ := columnType.Nullable(); !nullable {
+				t.Fatalf("bonus's nullable should be true, bug got %t", nullable)
+			}
+		case "stock":
+			// do not allow to change nullable to non-nullable
+			if nullable, _ := columnType.Nullable(); !nullable {
+				t.Fatalf("stock's nullable should be true, bug got %t", nullable)
+			}
 		case "birthday":
 			if precision, _, _ := columnType.DecimalSize(); (fullSupported || precision != 0) && precision != 2 {
 				t.Fatalf("birthday's precision should be 2, but got %v", precision)