Support for omitempty, as well as tests for omitempty.

encode.go

@@ -343,6 +343,21 @@ func (enc *Encoder) eStruct(key Key, rv reflect.Value) {
 			if keyName == "" {
 				keyName = sft.Name
 			}
+
+			opts := strings.Split(keyName, ",")
+			keyName = opts[0]
+			omitEmpty := false
+			if len(opts) > 1 {
+				for _, opt := range opts[1:] {
+					if opt == "omitempty" {
+						omitEmpty = true
+					}
+				}
+			}
+			if omitEmpty && isEmpty(sf) {
+				continue
+			}
+
 			enc.encode(key.add(keyName), sf)
 		}
 	}
@@ -433,6 +448,33 @@ func tomlArrayType(rv reflect.Value) tomlType {
 	return firstType
 }
 
+func isEmpty(rv reflect.Value) bool {
+	switch rv.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		if rv.Int() == 0 {
+			return true
+		}
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		if rv.Uint() == 0 {
+			return true
+		}
+	case reflect.Float32, reflect.Float64:
+		if rv.Float() == 0.0 {
+			return true
+		}
+	case reflect.String:
+		if len(strings.TrimSpace(rv.String())) == 0 {
+			return true
+		}
+	case reflect.Array, reflect.Slice, reflect.Map:
+		if rv.Len() == 0 {
+			return true
+		}
+	}
+
+	return false
+}
+
 func (enc *Encoder) newline() {
 	if enc.hasWritten {
 		enc.wf("\n")

encode_test.go

@@ -455,6 +455,20 @@ func TestEncodeArrayHashWithNormalHashOrder(t *testing.T) {
 	encodeExpected(t, "array hash with normal hash order", val, expected, nil)
 }
 
+func TestEncodeWithOmitEmpty(t *testing.T) {
+	type simple struct {
+		User string `toml:"user"`
+		Pass string `toml:"password,omitempty"`
+	}
+
+	value := simple{"Testing", ""}
+	expected := fmt.Sprintf("user = %q\n", value.User)
+	encodeExpected(t, "simple with omitempty, is empty", value, expected, nil)
+	value.Pass = "some password"
+	expected = fmt.Sprintf("user = %q\npassword = %q\n", value.User, value.Pass)
+	encodeExpected(t, "simple with omitempty, not empty", value, expected, nil)
+}
+
 func encodeExpected(
 	t *testing.T, label string, val interface{}, wantStr string, wantErr error,
 ) {