fix: WithErrors will check IsEmpty on an error container and avoid ad…

…ding it if empty.

causes.go

@@ -60,12 +60,23 @@ func (w *causes2) Defer(err *error) {
 }
 
 // WithErrors appends errs
+//
 // WithStackInfo.Attach() can only wrap and hold one child error object.
+//
+// WithErrors attach child errors into an error container.
+// For a container which has IsEmpty() interface, it would not be attach if it is empty (i.e. no errors).
+// For a nil error object, it will be ignored.
 func (w *causes2) WithErrors(errs ...error) *causes2 {
 	if len(errs) > 0 {
 		for _, e := range errs {
 			if e != nil {
-				w.Causers = append(w.Causers, e)
+				if check, ok := e.(interface{ IsEmpty() bool }); ok {
+					if check.IsEmpty() == false {
+						w.Causers = append(w.Causers, e)
+					}
+				} else {
+					w.Causers = append(w.Causers, e)
+				}
 			}
 		}
 	}

def.go

@@ -56,6 +56,7 @@ type Buildable interface {
 	WithCode(code Code) Buildable
 	// WithErrors attaches the given errs as inner errors.
 	// WithErrors is like our old Attach().
+	//
 	// It wraps the inner errors into underlying container and
 	// represents them all in a singular up-level error object.
 	// The wrapped inner errors can be retrieved with errors.Causes:
@@ -75,6 +76,9 @@ type Buildable interface {
 	//          e = errors.Unwrap(err)
 	//      }
 	//
+	// WithErrors attach child errors into an error container.
+	// For a container which has IsEmpty() interface, it would not be attach if it is empty (i.e. no errors).
+	// For a nil error object, it will be ignored.
 	WithErrors(errs ...error) Buildable
 	// WithData appends errs if the general object is a error object.
 	// It can be used in defer-recover block typically. For example:

errors.go

@@ -25,7 +25,9 @@ func New(args ...interface{}) Error {
 // Opt _
 type Opt func(s *builder)
 
-// WithErrors _
+// WithErrors attach child errors into an error container.
+// For a container which has IsEmpty() interface, it would not be attach if it is empty (i.e. no errors).
+// For a nil error object, it will be ignored.
 func WithErrors(errs ...error) Opt {
 	return func(s *builder) {
 		s.WithErrors(errs...)
@@ -70,6 +72,8 @@ type Builder interface {
 	// WithSkip specifies a special number of stack frames that will be ignored.
 	WithSkip(skip int) Builder
 	// WithErrors attaches the given errs as inner errors.
+	// For a container which has IsEmpty() interface, it would not be attach if it is empty (i.e. no errors).
+	// For a nil error object, it will be ignored.
 	WithErrors(errs ...error) Builder
 	// WithMessage formats the error message
 	WithMessage(message string, args ...interface{}) Builder
@@ -119,6 +123,8 @@ func (s *builder) WithMessage(message string, args ...interface{}) Builder {
 }
 
 // WithErrors attaches the given errs as inner errors.
+// For a container which has IsEmpty() interface, it would not be attach if it is empty (i.e. no errors).
+// For a nil error object, it will be ignored.
 func (s *builder) WithErrors(errs ...error) Builder {
 	_ = s.causes2.WithErrors(errs...)
 	return s