Merge pull request #5 from popescu-af/4/pass_allow_unknown_flag

Pass allow unknown flag to row scanner.

exec_test.go

@@ -63,6 +63,7 @@ func createQuery(tb testing.TB, cols []string) string {
 }
 
 type queryCase[T any] struct {
+	ctx         context.Context
 	columns     strstr
 	rows        rows
 	query       []string // columns to select
@@ -76,7 +77,10 @@ func testQuery[T any](t *testing.T, name string, tc queryCase[T]) {
 	t.Helper()
 
 	t.Run(name, func(t *testing.T) {
-		ctx := context.Background()
+		ctx := tc.ctx
+		if ctx == nil {
+			ctx = context.Background()
+		}
 
 		ex, clean := createDB(t, tc.columns)
 		defer clean()
@@ -283,3 +287,30 @@ func TestStruct(t *testing.T) {
 		},
 	})
 }
+
+func TestAllowUnknownColumns(t *testing.T) {
+	type testStruct struct {
+		ID  int64
+		Int int64
+	}
+
+	// fails when context does not have CtxKeyAllowUnknownColumns set to true
+	testQuery(t, "unknowncolumnsnotallowed", queryCase[testStruct]{
+		columns:     strstr{{"id", "int64"}, {"ignored_int", "int64"}, {"int", "int64"}},
+		rows:        rows{{1, 10, 1}, {2, 20, 2}},
+		query:       []string{"id", "ignored_int", "int"},
+		mapper:      StructMapper[testStruct](),
+		expectedErr: createError(fmt.Errorf("No destination for column ignored_int"), "no destination", "ignored_int"),
+	})
+
+	// succeeds when context has CtxKeyAllowUnknownColumns set to true
+	testQuery(t, "unknowncolumnsallowed", queryCase[testStruct]{
+		ctx:       context.WithValue(context.Background(), CtxKeyAllowUnknownColumns, true),
+		columns:   strstr{{"id", "int64"}, {"ignored_int", "int64"}, {"int", "int64"}},
+		rows:      rows{{1, 10, 1}, {2, 20, 2}},
+		query:     []string{"id", "ignored_int", "int"},
+		mapper:    StructMapper[testStruct](),
+		expectOne: testStruct{ID: 1, Int: 1},
+		expectAll: []testStruct{{ID: 1, Int: 1}, {ID: 2, Int: 2}},
+	})
+}

row.go

@@ -17,6 +17,7 @@ func wrapRows(r Rows, allowUnknown bool) (*Row, error) {
 		r:                r,
 		columns:          cols,
 		scanDestinations: make([]reflect.Value, len(cols)),
+		allowUnknown:     allowUnknown,
 	}, nil
 }
 
@@ -64,6 +65,21 @@ func (r *Row) scanCurrentRow() error {
 		return createError(fmt.Errorf("unknown columns to map to: %v", r.unknownDestinations), r.unknownDestinations...)
 	}
 
+	targets, err := r.createTargets()
+	if err != nil {
+		return err
+	}
+
+	err = r.r.Scan(targets...)
+	if err != nil {
+		return err
+	}
+
+	r.scanDestinations = make([]reflect.Value, len(r.columns))
+	return nil
+}
+
+func (r *Row) createTargets() ([]any, error) {
 	targets := make([]any, len(r.columns))
 
 	for i, name := range r.columns {
@@ -75,15 +91,14 @@ func (r *Row) scanCurrentRow() error {
 
 		if !r.allowUnknown {
 			err := fmt.Errorf("No destination for column %s", name)
-			return createError(err, "no destination", name)
+			return nil, createError(err, "no destination", name)
 		}
-	}
 
-	err := r.r.Scan(targets...)
-	if err != nil {
-		return err
+		// See https://github.com/golang/go/issues/41607:
+		// Some drivers cannot work with nil values, so valid pointers should be
+		// used for all column targets, even if they are discarded afterwards.
+		targets[i] = new(interface{})
 	}
 
-	r.scanDestinations = make([]reflect.Value, len(r.columns))
-	return nil
+	return targets, nil
 }