Return an empty array from ValueWithShadows if there is none (#313)

Co-authored-by: Joe Chen <jc@unknwon.io>

.editorconfig

@@ -7,3 +7,6 @@ charset = utf-8
 end_of_line = lf
 insert_final_newline = true
 trim_trailing_whitespace = true
+
+[*_test.go]
+trim_trailing_whitespace = false

file.go

@@ -442,16 +442,16 @@ func (f *File) writeToBuffer(indent string) (*bytes.Buffer, error) {
 				kname = `"""` + kname + `"""`
 			}
 
-			for _, val := range key.ValueWithShadows() {
+			writeKeyValue := func(val string) (bool, error) {
 				if _, err := buf.WriteString(kname); err != nil {
-					return nil, err
+					return false, err
 				}
 
 				if key.isBooleanType {
 					if kname != sec.keyList[len(sec.keyList)-1] {
 						buf.WriteString(LineBreak)
 					}
-					continue KeyList
+					return true, nil
 				}
 
 				// Write out alignment spaces before "=" sign
@@ -468,10 +468,27 @@ func (f *File) writeToBuffer(indent string) (*bytes.Buffer, error) {
 					val = `"` + val + `"`
 				}
 				if _, err := buf.WriteString(equalSign + val + LineBreak); err != nil {
+					return false, err
+				}
+				return false, nil
+			}
+
+			shadows := key.ValueWithShadows()
+			if len(shadows) == 0 {
+				if _, err := writeKeyValue(""); err != nil {
 					return nil, err
 				}
 			}
 
+			for _, val := range shadows {
+				exitLoop, err := writeKeyValue(val)
+				if err != nil {
+					return nil, err
+				} else if exitLoop {
+					continue KeyList
+				}
+			}
+
 			for _, val := range key.nestedValues {
 				if _, err := buf.WriteString(indent + "  " + val + LineBreak); err != nil {
 					return nil, err

key.go

@@ -113,6 +113,9 @@ func (k *Key) Value() string {
 // ValueWithShadows returns raw values of key and its shadows if any.
 func (k *Key) ValueWithShadows() []string {
 	if len(k.shadows) == 0 {
+		if k.value == "" {
+			return []string{}
+		}
 		return []string{k.value}
 	}
 	vals := make([]string, len(k.shadows)+1)

key_test.go

@@ -521,6 +521,25 @@ func TestKey_Helpers(t *testing.T) {
 	})
 }
 
+func TestKey_ValueWithShadows(t *testing.T) {
+	t.Run("", func(t *testing.T) {
+		f, err := ShadowLoad([]byte(`
+keyName = value1
+keyName = value2
+`))
+		require.NoError(t, err)
+		require.NotNil(t, f)
+
+		k := f.Section("").Key("FakeKey")
+		require.NotNil(t, k)
+		assert.Equal(t, []string{}, k.ValueWithShadows())
+
+		k = f.Section("").Key("keyName")
+		require.NotNil(t, k)
+		assert.Equal(t, []string{"value1", "value2"}, k.ValueWithShadows())
+	})
+}
+
 func TestKey_StringsWithShadows(t *testing.T) {
 	t.Run("get strings of shadows of a key", func(t *testing.T) {
 		f, err := ShadowLoad([]byte(""))