fix suspend with cause bug (#16)

Author: lysu

juju_adaptor.go

@@ -66,18 +66,37 @@ func NewNoStackError(msg string) error {
 	}
 }
 
-// SuspendStack suspends stack for a exists error.
-// it can be used to suspend follow up Trace do not add stack.
+// SuspendStack suspends stack generate for error.
 func SuspendStack(err error) error {
 	if err == nil {
 		return err
 	}
-	return withStack{
+	cleared := clearStack(err)
+	if cleared {
+		return err
+	}
+	return &withStack{
 		err,
 		&emptyStack,
 	}
 }
 
+func clearStack(err error) (cleared bool) {
+	switch typedErr := err.(type) {
+	case *withMessage:
+		return clearStack(typedErr.Cause())
+	case *fundamental:
+		typedErr.stack = &emptyStack
+		return true
+	case *withStack:
+		typedErr.stack = &emptyStack
+		clearStack(typedErr.Cause())
+		return true
+	default:
+		return false
+	}
+}
+
 // ErrorStack will format a stack trace if it is available, otherwise it will be Error()
 // If the error is nil, the empty string is returned
 // Note that this just calls fmt.Sprintf("%+v", err)

stack_test.go

@@ -299,12 +299,27 @@ func TestNewNoStackError(t *testing.T) {
 	}
 }
 
-func TestSuspendStackError(t *testing.T) {
+func TestSuspendError(t *testing.T) {
 	err := io.EOF
 	err = SuspendStack(err)
 	err = Trace(err)
 	result := fmt.Sprintf("%+v", err)
 	if result != "EOF" {
 		t.Errorf("NewNoStackError(): want %s, got %v", "EOF", result)
 	}
+	if io.EOF != Cause(err) {
+		t.Errorf("SuspendStackError can not got back origion error.")
+	}
+}
+
+func TestSuspendTracedWithMessageError(t *testing.T) {
+	tracedErr := Trace(io.EOF)
+	tracedErr = WithStack(tracedErr)
+	tracedErr = WithMessage(tracedErr, "1")
+	tracedErr = SuspendStack(tracedErr)
+	tracedErr = Trace(tracedErr)
+	result := fmt.Sprintf("%+v", tracedErr)
+	if result != "EOF\n1" {
+		t.Errorf("NewNoStackError(): want %s, got %v", "EOF\n1", result)
+	}
 }