validate: imp append

netutil/httputil/logmw.go

@@ -66,7 +66,7 @@ func (mw *LogMiddleware) Wrap(h http.Handler) (wrapped http.Handler) {
 		rw.Reset(w)
 
 		l.Log(ctx, mw.lvl, "started")
-		defer mw.printFinished(ctx, l, rw, startTime)
+		defer mw.logFinished(ctx, l, rw, startTime)
 
 		h.ServeHTTP(rw, nextReq)
 		rw.SetImplicitSuccess()
@@ -75,8 +75,8 @@ func (mw *LogMiddleware) Wrap(h http.Handler) (wrapped http.Handler) {
 	return http.HandlerFunc(f)
 }
 
-// printFinished is called at the end of handling of a query.
-func (mw *LogMiddleware) printFinished(
+// logFinished is called at the end of handling of a query.
+func (mw *LogMiddleware) logFinished(
 	ctx context.Context,
 	l *slog.Logger,
 	rw *CodeRecorderResponseWriter,

validate/validate.go

@@ -28,9 +28,21 @@ type Interface interface {
 	Validate() (err error)
 }
 
-// Append validates values, wraps errors with the name and the index, appends
-// them to errs, and returns the result.
-func Append[T Interface](errs []error, name string, values []T) (res []error) {
+// Append validates v and, if it returns an error, appends it to errs and
+// returns the result.
+func Append(errs []error, name string, v Interface) (res []error) {
+	res = errs
+	err := v.Validate()
+	if err != nil {
+		res = append(res, fmt.Errorf("%s: %w", name, err))
+	}
+
+	return res
+}
+
+// AppendSlice validates values, wraps errors with the name and the index,
+// appends them to errs, and returns the result.
+func AppendSlice[T Interface](errs []error, name string, values []T) (res []error) {
 	res = errs
 	for i, v := range values {
 		// TODO(a.garipov):  Consider flattening error slices.
@@ -46,7 +58,7 @@ func Append[T Interface](errs []error, name string, values []T) (res []error) {
 // Slice validates values, wraps errors with the name and the index, and returns
 // the result as a single joined error.
 func Slice[T Interface](name string, values []T) (err error) {
-	return errors.Join(Append(nil, name, values)...)
+	return errors.Join(AppendSlice(nil, name, values)...)
 }
 
 // InRange returns an error of v is less than min or greater than max.  The

validate/validate_example_test.go

@@ -21,6 +21,25 @@ func (v *value) Validate() (err error) {
 	return v.err
 }
 
+func ExampleAppend() {
+	var errs []error
+
+	var (
+		badValue = &value{
+			err: errors.Error("test error"),
+		}
+		goodValue = &value{}
+	)
+
+	errs = validate.Append(errs, "first_value", goodValue)
+	errs = validate.Append(errs, "second_value", badValue)
+
+	fmt.Println(errors.Join(errs...))
+
+	// Output:
+	// second_value: test error
+}
+
 func ExampleSlice() {
 	values := []*value{
 		0: {