fix: check empty key (#15)

encoder.go

@@ -81,6 +81,9 @@ func (e *Encoder) Sdump(i interface{}) (string, error) {
 func (e *Encoder) fdumpInterface(w map[string]interface{}, i interface{}, roots []string) error {
 	f := valueFromInterface(i)
 	if !validAndNotEmpty(f) {
+		if len(roots) == 0 {
+			return nil
+		}
 		k := fmt.Sprintf("%s", strings.Join(sliceFormat(roots, e.Formatters), "."))
 		w[k] = ""
 		return nil

test/dump_test.go

@@ -398,6 +398,24 @@ value: bar
 	assert.Equal(t, expected, out.String())
 }
 
+func TestMapEmptyInterface(t *testing.T) {
+	myMap := make(map[string]interface{})
+	myMap[""] = "empty"
+
+	result, err := dump.ToStringMap(myMap)
+	t.Log(dump.Sdump(myMap))
+	assert.NoError(t, err)
+	assert.Equal(t, 2, len(result))
+
+	expected := `__len__: 0
+__type__: Map
+`
+	out := &bytes.Buffer{}
+	err = dump.Fdump(out, myMap, dump.WithDefaultLowerCaseFormatter())
+	assert.NoError(t, err)
+	assert.Equal(t, expected, out.String())
+}
+
 func TestFromJSON(t *testing.T) {
 	js := []byte(`{
     "blabla": "lol log",