feat: add bun.NullZero

bun.go

@@ -83,3 +83,7 @@ func SetLogger(logger internal.Logging) {
 func In(slice interface{}) schema.QueryAppender {
 	return schema.In(slice)
 }
+
+func NullZero(value interface{}) schema.QueryAppender {
+	return schema.NullZero(value)
+}

internal/dbtest/query_test.go

@@ -986,6 +986,9 @@ func TestQuery(t *testing.T) {
 			// Non-positive VARCHAR length is illegal
 			return db.NewCreateTable().Model((*Model)(nil)).Varchar(-20)
 		},
+		func(db *bun.DB) schema.QueryAppender {
+			return db.NewUpdate().TableExpr("xxx").Set("foo = ?", bun.NullZero("")).Where("1")
+		},
 	}
 
 	timeRE := regexp.MustCompile(`'2\d{3}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}(\.\d+)?(\+\d{2}:\d{2})?'`)

internal/dbtest/testdata/snapshots/TestQuery-mariadb-158

@@ -0,0 +1 @@
+UPDATE xxx SET foo = NULL WHERE (1)

internal/dbtest/testdata/snapshots/TestQuery-mssql2019-158

@@ -0,0 +1 @@
+UPDATE xxx SET foo = NULL WHERE (1)

internal/dbtest/testdata/snapshots/TestQuery-mysql5-158

@@ -0,0 +1 @@
+UPDATE xxx SET foo = NULL WHERE (1)

internal/dbtest/testdata/snapshots/TestQuery-mysql8-158

@@ -0,0 +1 @@
+UPDATE xxx SET foo = NULL WHERE (1)

internal/dbtest/testdata/snapshots/TestQuery-pg-158

@@ -0,0 +1 @@
+UPDATE xxx SET foo = NULL WHERE (1)

internal/dbtest/testdata/snapshots/TestQuery-pgx-158

@@ -0,0 +1 @@
+UPDATE xxx SET foo = NULL WHERE (1)

internal/dbtest/testdata/snapshots/TestQuery-sqlite-158

@@ -0,0 +1 @@
+UPDATE xxx SET foo = NULL WHERE (1)

schema/append.go

@@ -81,7 +81,7 @@ func appendIn(fmter Formatter, b []byte, slice reflect.Value) []byte {
 	sliceLen := slice.Len()
 
 	if sliceLen == 0 {
-		return append(b, "NULL"...)
+		return dialect.AppendNull(b)
 	}
 
 	for i := 0; i < sliceLen; i++ {
@@ -104,3 +104,22 @@ func appendIn(fmter Formatter, b []byte, slice reflect.Value) []byte {
 	}
 	return b
 }
+
+//------------------------------------------------------------------------------
+
+func NullZero(value interface{}) QueryAppender {
+	return nullZero{
+		value: value,
+	}
+}
+
+type nullZero struct {
+	value interface{}
+}
+
+func (nz nullZero) AppendQuery(fmter Formatter, b []byte) (_ []byte, err error) {
+	if isZero(nz.value) {
+		return dialect.AppendNull(b), nil
+	}
+	return fmter.AppendValue(b, reflect.ValueOf(nz.value)), nil
+}

schema/zerochecker.go

@@ -11,6 +11,45 @@ type isZeroer interface {
 	IsZero() bool
 }
 
+func isZero(v interface{}) bool {
+	switch v := v.(type) {
+	case isZeroer:
+		return v.IsZero()
+	case string:
+		return v == ""
+	case []byte:
+		return v == nil
+	case int:
+		return v == 0
+	case int64:
+		return v == 0
+	case uint:
+		return v == 0
+	case uint64:
+		return v == 0
+	case float32:
+		return v == 0
+	case float64:
+		return v == 0
+	case int8:
+		return v == 0
+	case int16:
+		return v == 0
+	case int32:
+		return v == 0
+	case uint8:
+		return v == 0
+	case uint16:
+		return v == 0
+	case uint32:
+		return v == 0
+	default:
+		rv := reflect.ValueOf(v)
+		fn := zeroChecker(rv.Type())
+		return fn(rv)
+	}
+}
+
 type IsZeroerFunc func(reflect.Value) bool
 
 func zeroChecker(typ reflect.Type) IsZeroerFunc {