WithContext Wrap and Wrapf should return nil if wrapped err is nil

errors/with_context.go

@@ -19,7 +19,13 @@ type HasFormat interface {
 // Creates errors that conform to the `HasContext` interface
 type WithContext map[string]interface{}
 
+// Wrapf returns an error annotating err with a stack trace
+// at the point Wrapf is call, and the format specifier.
+// If err is nil, Wrapf returns nil.
 func (c WithContext) Wrapf(err error, format string, args ...interface{}) error {
+	if err == nil {
+		return nil
+	}
 	return &withContext{
 		stack:   stack.New(1),
 		context: c,
@@ -28,7 +34,13 @@ func (c WithContext) Wrapf(err error, format string, args ...interface{}) error
 	}
 }
 
+// Wrap returns an error annotating err with a stack trace
+// at the point Wrap is called, and the supplied message.
+// If err is nil, Wrap returns nil.
 func (c WithContext) Wrap(err error, msg string) error {
+	if err == nil {
+		return nil
+	}
 	return &withContext{
 		stack:   stack.New(1),
 		context: c,

errors/with_context_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/mailgun/holster/errors"
 	"github.com/mailgun/holster/stack"
 	. "gopkg.in/check.v1"
+	"github.com/ahmetb/go-linq"
 )
 
 type TestError struct {
@@ -66,3 +67,13 @@ func (s *WithContextTestSuite) TestWithStack(c *C) {
 	c.Assert(linq.From(files).Contains("with_context_test.go"), Equals, true)
 	c.Assert(linq.From(funcs).Contains("(*WithContextTestSuite).TestWithStack"), Equals, true)
 }
+
+func (s *WithContextTestSuite) TestWrapfNil(c *C) {
+	got := errors.WithContext{"some": "context"}.Wrapf(nil, "no error")
+	c.Assert(got, IsNil)
+}
+
+func (s *WithContextTestSuite) TestWrapNil(c *C) {
+	got := errors.WithContext{"some": "context"}.Wrap(nil, "no error")
+	c.Assert(got, IsNil)
+}