add SuspendStack support (#15)

Author: lysu

juju_adaptor.go

@@ -66,6 +66,18 @@ 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.
+func SuspendStack(err error) error {
+	if err == nil {
+		return err
+	}
+	return withStack{
+		err,
+		&emptyStack,
+	}
+}
+
 // 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

@@ -2,6 +2,7 @@ package errors
 
 import (
 	"fmt"
+	"io"
 	"runtime"
 	"testing"
 )
@@ -288,7 +289,7 @@ func TestNewStack(t *testing.T) {
 	}
 }
 
-func TestSuspendStackError(t *testing.T) {
+func TestNewNoStackError(t *testing.T) {
 	err := NewNoStackError("test error")
 	err = Trace(err)
 	err = Trace(err)
@@ -297,3 +298,13 @@ func TestSuspendStackError(t *testing.T) {
 		t.Errorf("NewNoStackError(): want %s, got %v", "test error", result)
 	}
 }
+
+func TestSuspendStackError(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)
+	}
+}