Fix optional and pointers

borsh_test.go

@@ -13,6 +13,95 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+type OptionalPointerFields struct {
+	Good uint8
+	Arr  *Arr `bin:"optional"`
+}
+
+type Arr []string
+
+func TestOptionWithPointer(t *testing.T) {
+	// nil (optional not present)
+	{
+		buf := new(bytes.Buffer)
+		enc := NewBorshEncoder(buf)
+		val := OptionalPointerFields{
+			Good: 9,
+			// Will be decoded as nil pointer.
+			Arr: nil,
+		}
+		require.NoError(t, enc.Encode(val))
+		require.Equal(t,
+			concatByteSlices(
+				[]byte{9},
+				[]byte{0},
+			),
+			buf.Bytes())
+		{
+			dec := NewBorshDecoder(buf.Bytes())
+			var got OptionalPointerFields
+			require.NoError(t, dec.Decode(&got))
+			require.Equal(t, val, got)
+		}
+	}
+	// optional is present but has zero elements
+	{
+		buf := new(bytes.Buffer)
+		enc := NewBorshEncoder(buf)
+		val := OptionalPointerFields{
+			Good: 9,
+			// Will be decoded as pointer to nil Arr.
+			Arr: &Arr{},
+		}
+		require.NoError(t, enc.Encode(val))
+		require.Equal(t,
+			concatByteSlices(
+				[]byte{9},
+				[]byte{1},
+				[]byte{0, 0, 0, 0},
+			),
+			buf.Bytes(),
+		)
+		{
+			dec := NewBorshDecoder(buf.Bytes())
+			var got OptionalPointerFields
+			require.NoError(t, dec.Decode(&got))
+			// an empty slice is decoded as nil.
+			po := (Arr)(nil)
+			val.Arr = &po
+			require.Equal(t,
+				val, got)
+		}
+	}
+	// optional is present and has elements
+	{
+		buf := new(bytes.Buffer)
+		enc := NewBorshEncoder(buf)
+		val := OptionalPointerFields{
+			Good: 9,
+			Arr:  &Arr{"foo"},
+		}
+		require.NoError(t, enc.Encode(val))
+		require.Equal(t,
+			concatByteSlices(
+				[]byte{9},
+				[]byte{1},
+				[]byte{1, 0, 0, 0},
+
+				[]byte{3, 0, 0, 0},
+				[]byte("foo"),
+			),
+			buf.Bytes(),
+		)
+		{
+			dec := NewBorshDecoder(buf.Bytes())
+			var got OptionalPointerFields
+			require.NoError(t, dec.Decode(&got))
+			require.Equal(t, val, got)
+		}
+	}
+}
+
 type StructWithComplexPeculiarEnums struct {
 	Complex2NotSet    ComplexEnumPointers
 	Complex2PtrNotSet *ComplexEnumPointers

decoder_borsh.go

@@ -39,7 +39,6 @@ func (dec *Decoder) decodeBorsh(rv reflect.Value, opt *option) (err error) {
 		)
 	}
 
-	// TODO: is `rv.Kind() == reflect.Ptr` correct here???
 	if opt.isOptional() {
 		isPresent, e := dec.ReadByte()
 		if e != nil {
@@ -59,6 +58,8 @@ func (dec *Decoder) decodeBorsh(rv reflect.Value, opt *option) (err error) {
 		// we have ptr here we should not go get the element
 		unmarshaler, rv = indirect(rv, false)
 	}
+	// Reset optionality so it won't propagate to child types:
+	opt = opt.clone().setIsOptional(false)
 
 	if unmarshaler != nil {
 		if traceEnabled {

encoder_borsh.go

@@ -23,7 +23,7 @@ func (e *Encoder) encodeBorsh(rv reflect.Value, opt *option) (err error) {
 	}
 
 	if opt.isOptional() {
-		if rv.IsZero() || (rv.Kind() == reflect.Ptr && rv.IsNil()) {
+		if rv.IsZero() {
 			if traceEnabled {
 				zlog.Debug("encode: skipping optional value with", zap.Stringer("type", rv.Kind()))
 			}
@@ -32,6 +32,8 @@ func (e *Encoder) encodeBorsh(rv reflect.Value, opt *option) (err error) {
 		}
 		e.WriteBool(true)
 	}
+	// Reset optionality so it won't propagate to child types:
+	opt = opt.clone().setIsOptional(false)
 
 	if isZero(rv) {
 		return nil
@@ -78,8 +80,8 @@ func (e *Encoder) encodeBorsh(rv reflect.Value, opt *option) (err error) {
 		return e.WriteBool(rv.Bool())
 	case reflect.Ptr:
 		if rv.IsNil() {
-			// el := reflect.New(rv.Type().Elem()).Elem()
-			// return e.encodeBorsh(el, nil)
+			el := reflect.New(rv.Type().Elem()).Elem()
+			return e.encodeBorsh(el, nil)
 		} else {
 			return e.encodeBorsh(rv.Elem(), nil)
 		}