Allow marshal to bytes buffer

viper.go

@@ -1704,6 +1704,15 @@ func (v *Viper) SafeWriteConfigAs(filename string) error {
 	return v.writeConfig(filename, false)
 }
 
+// Marshal will return a Buffer containing the content that should have been written to the file
+func (v *Viper) Marshal() (*bytes.Buffer, error) {
+	data, err := v.encoderRegistry.Encode(v.getConfigType(), v.AllSettings())
+	if err != nil {
+		return nil, err
+	}
+	return bytes.NewBuffer(data), nil
+}
+
 func (v *Viper) writeConfig(filename string, force bool) error {
 	v.logger.Info("attempting to write configuration to file")
 

viper_test.go

@@ -1979,6 +1979,15 @@ func TestSafeWriteConfigAsWithExistingFile(t *testing.T) {
 	assert.True(t, ok, "Expected ConfigFileAlreadyExistsError")
 }
 
+func TestMarshal(t *testing.T) {
+	v := New()
+	v.SetConfigType("yaml")
+	require.NoError(t, v.ReadConfig(bytes.NewBuffer(yamlExample)))
+	c, err := v.Marshal()
+	require.NoError(t, err)
+	assert.Equal(t, c.Bytes(), yamlWriteExpected)
+}
+
 func TestWriteHiddenFile(t *testing.T) {
 	v := New()
 	fs := afero.NewMemMapFs()