fix(insert): keep field in VALUES when any slice element has a non-default value

internal/dbtest/issue1394_test.go

@@ -0,0 +1,60 @@
+package dbtest_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/uptrace/bun"
+)
+
+// TestIssue1394_DroppedFieldValueOnSliceInsert reproduces issue #1394:
+// when inserting a slice of structs, getFields() only inspected the first
+// element to decide which fields marshal to DEFAULT (and should therefore
+// go to the RETURNING clause instead of the VALUES clause). If a later
+// element carried a real value for such a field, it was silently dropped
+// from the INSERT and never reached the database.
+//
+// This test uses only SQLite so it runs without external services.
+func TestIssue1394_DroppedFieldValueOnSliceInsert(t *testing.T) {
+	ctx := context.Background()
+
+	type Issue1394Model struct {
+		bun.BaseModel `bun:"table:issue_1394_models,alias:im"`
+
+		ID    int64  `bun:",pk,autoincrement"`
+		Name  string `bun:",notnull"`
+		Email string `bun:",notnull,default:'none'"`
+	}
+
+	db := sqlite(t)
+
+	mustResetModel(t, ctx, db, (*Issue1394Model)(nil))
+
+	// First element has a zero Email; second element has a real Email.
+	// Before the fix, getFields() inspected only the first element, saw
+	// Email is NotNull + marshalsToDefault (zero value + SQLDefault), and
+	// moved Email to RETURNING — so Email was dropped from the INSERT
+	// column list entirely. The second element's "alice@example.com" was
+	// silently replaced by the column's DEFAULT ('none').
+	models := []Issue1394Model{
+		{Name: "zero-email"},
+		{Name: "with-email", Email: "alice@example.com"},
+	}
+
+	_, err := db.NewInsert().Model(&models).Exec(ctx)
+	require.NoError(t, err)
+
+	var got []Issue1394Model
+	err = db.NewSelect().Model(&got).OrderExpr("im.id ASC").Scan(ctx)
+	require.NoError(t, err)
+
+	require.Len(t, got, 2)
+	require.Equal(t, "zero-email", got[0].Name)
+	require.Equal(t, "none", got[0].Email,
+		"first row had no email, so the column DEFAULT ('none') applies")
+	require.Equal(t, "with-email", got[1].Name)
+	require.Equal(t, "alice@example.com", got[1].Email,
+		"second row's Email must be persisted, not silently dropped (issue #1394)")
+}

query_insert.go

@@ -425,6 +425,7 @@ func (q *InsertQuery) getFields() ([]*schema.Field, error) {
 	}
 
 	var strct reflect.Value
+	var slice reflect.Value
 
 	switch model := q.tableModel.(type) {
 	case *structTableModel:
@@ -433,7 +434,7 @@ func (q *InsertQuery) getFields() ([]*schema.Field, error) {
 		if model.sliceLen == 0 {
 			return nil, fmt.Errorf("bun: Insert(empty %T)", model.slice.Type())
 		}
-		strct = indirect(model.slice.Index(0))
+		slice = model.slice
 	default:
 		return nil, errNilModel
 	}
@@ -445,7 +446,7 @@ func (q *InsertQuery) getFields() ([]*schema.Field, error) {
 			q.addReturningField(f)
 			continue
 		}
-		if f.NotNull && q.marshalsToDefault(f, strct) {
+		if f.NotNull && q.marshalsToDefaultForInsert(f, strct, slice) {
 			q.addReturningField(f)
 			continue
 		}
@@ -455,6 +456,24 @@ func (q *InsertQuery) getFields() ([]*schema.Field, error) {
 	return fields, nil
 }
 
+// marshalsToDefaultForInsert reports whether f marshals to DEFAULT/NULL for
+// every row being inserted. For a single-struct model it checks the one
+// struct; for a slice model it checks every element, so that a field is only
+// moved to RETURNING when no element carries a real value. Otherwise a later
+// element's value would be silently dropped from the INSERT (issue #1394).
+func (q InsertQuery) marshalsToDefaultForInsert(f *schema.Field, strct, slice reflect.Value) bool {
+	if !slice.IsValid() {
+		return q.marshalsToDefault(f, strct)
+	}
+	n := slice.Len()
+	for i := 0; i < n; i++ {
+		if !q.marshalsToDefault(f, indirect(slice.Index(i))) {
+			return false
+		}
+	}
+	return true
+}
+
 // marshalsToDefault checks if the value will be marshaled as DEFAULT or NULL (if DEFAULT placeholder is not supported)
 // when appending it to the VALUES clause in place of the given field.
 func (q InsertQuery) marshalsToDefault(f *schema.Field, v reflect.Value) bool {