fix: fix OmitZero and value overriding

internal/dbtest/query_test.go

@@ -786,6 +786,18 @@ func TestQuery(t *testing.T) {
 				WherePK().
 				WhereAllWithDeleted()
 		},
+		func(db *bun.DB) schema.QueryAppender {
+			type Model struct {
+				ID        int64 `bun:",pk"`
+				UpdatedAt time.Time
+			}
+			return db.NewUpdate().
+				Model(&Model{}).
+				OmitZero().
+				WherePK().
+				Value("updated_at", "NOW()").
+				Returning("*")
+		},
 	}
 
 	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-130

@@ -0,0 +1 @@
+UPDATE `models` AS `model` SET `updated_at` = NOW() WHERE (`model`.`id` = 0)

internal/dbtest/testdata/snapshots/TestQuery-mssql2019-130

@@ -0,0 +1 @@
+UPDATE "models" SET "updated_at" = NOW() WHERE ("id" = 0)

internal/dbtest/testdata/snapshots/TestQuery-mysql5-130

@@ -0,0 +1 @@
+UPDATE `models` AS `model` SET `updated_at` = NOW() WHERE (`model`.`id` = 0)

internal/dbtest/testdata/snapshots/TestQuery-mysql8-130

@@ -0,0 +1 @@
+UPDATE `models` AS `model` SET `updated_at` = NOW() WHERE (`model`.`id` = 0)

internal/dbtest/testdata/snapshots/TestQuery-pg-130

@@ -0,0 +1 @@
+UPDATE "models" AS "model" SET "updated_at" = NOW() WHERE ("model"."id" = 0) RETURNING *

internal/dbtest/testdata/snapshots/TestQuery-pgx-130

@@ -0,0 +1 @@
+UPDATE "models" AS "model" SET "updated_at" = NOW() WHERE ("model"."id" = 0) RETURNING *

internal/dbtest/testdata/snapshots/TestQuery-sqlite-130

@@ -0,0 +1 @@
+UPDATE "models" AS "model" SET "updated_at" = NOW() WHERE ("model"."id" = 0) RETURNING *

query_update.go

@@ -273,7 +273,9 @@ func (q *UpdateQuery) appendSetStruct(
 	isTemplate := fmter.IsNop()
 	pos := len(b)
 	for _, f := range fields {
-		if q.omitZero && f.HasZeroValue(model.strct) {
+		app, hasValue := q.modelValues[f.Name]
+
+		if !hasValue && q.omitZero && f.HasZeroValue(model.strct) {
 			continue
 		}
 
@@ -290,8 +292,7 @@ func (q *UpdateQuery) appendSetStruct(
 			continue
 		}
 
-		app, ok := q.modelValues[f.Name]
-		if ok {
+		if hasValue {
 			b, err = app.AppendQuery(fmter, b)
 			if err != nil {
 				return nil, err