Added Formatter interface

errors.go

@@ -92,6 +92,37 @@ func (p *Error) Error() string {
 	return output.String()
 }
 
+func (p *Error) Format(f fmt.State, verb rune) {
+	var s string
+
+	switch verb {
+	case 's', 'v':
+		if f.Flag('+') {
+			s = p.VerboseString()
+		} else if f.Flag('#') {
+			s = p.GoString()
+		} else {
+			s = p.Error()
+		}
+	}
+
+	if s == "" {
+		fmt.Fprint(f, p)
+	} else {
+		_, _ = f.Write([]byte(s))
+	}
+}
+
+func (p *Error) GoString() string {
+	isRetryable := "nil"
+	if p.IsRetryable != nil {
+		isRetryable = fmt.Sprintf("%#v", *p.IsRetryable)
+	}
+	return fmt.Sprintf("&terrors.Error{Code: %q, Message: %q, Params: %#v, StackFrames: %#v, IsRetryable: %s, cause: %#v}",
+		p.Code, p.Message, p.Params, p.StackFrames, isRetryable, p.cause,
+	)
+}
+
 func (p *Error) legacyErrString() string {
 	if p == nil {
 		return ""

errors_test.go

@@ -481,3 +481,22 @@ func TestRetryable(t *testing.T) {
 		})
 	}
 }
+
+func TestFormat(t *testing.T) {
+	err := New("test", "Test", map[string]string{"flavour": "banana"})
+
+	assert.Equal(t, err.Error(),
+		fmt.Sprintf("%v", err))
+	assert.Equal(t, err.VerboseString(),
+		fmt.Sprintf("%+v", err))
+
+	goStringErr := fmt.Sprintf("%#v", err)
+	goStringErrPrefix := `&terrors.Error{Code: "test", Message: "Test", Params: map[string]string{"flavour":"banana"}, StackFrames: []*stack.Frame{`
+	assert.Equal(t, goStringErrPrefix, goStringErr[0:len(goStringErrPrefix)])
+
+	goStringErrSuffix := `}, IsRetryable: false, cause: <nil>}`
+	assert.Equal(t, goStringErrSuffix, goStringErr[len(goStringErr)-len(goStringErrSuffix):])
+
+	assert.Equal(t, err.Error(),
+		fmt.Sprintf("%d", err))
+}

stack/stack.go

@@ -27,6 +27,19 @@ type Frame struct {
 
 type Stack []*Frame
 
+func (s Stack) GoString() string {
+	b := strings.Builder{}
+
+	if len(s) > 0 {
+		b.WriteString(fmt.Sprintf("&%#v", *s[0]))
+		for _, f := range s[1:] {
+			b.WriteString(fmt.Sprintf(", &%#v", *f))
+		}
+	}
+
+	return fmt.Sprintf("[]*stack.Frame{%s}", b.String())
+}
+
 func BuildStack(skip int) Stack {
 	stack := make(Stack, 0)