add tests that codify the cases where encoded output can't be decoded without error

Author: roberto-bayardo

rlp/decode_test.go

@@ -439,6 +439,16 @@ type optionalPtrField struct {
 	B *[3]byte `rlp:"optional"`
 }
 
+type nonOptionalPtrField struct {
+	A uint
+	B *[3]byte
+}
+
+type multipleOptionalFields struct {
+	A *[3]byte `rlp:"optional"`
+	B *[3]byte `rlp:"optional"`
+}
+
 type optionalPtrFieldNil struct {
 	A uint
 	B *[3]byte `rlp:"optional,nil"`
@@ -744,6 +754,30 @@ var decodeTests = []decodeTest{
 		ptr:   new(optionalPtrField),
 		value: optionalPtrField{A: 1, B: &[3]byte{1, 2, 3}},
 	},
+	{
+		// all optional fields nil
+		input: "C0",
+		ptr:   new(multipleOptionalFields),
+		value: multipleOptionalFields{A: nil, B: nil},
+	},
+	{
+		// all optional fields set
+		input: "C88301020383010203",
+		ptr:   new(multipleOptionalFields),
+		value: multipleOptionalFields{A: &[3]byte{1, 2, 3}, B: &[3]byte{1, 2, 3}},
+	},
+	{
+		// nil optional field appears before a non-nil one
+		input: "C58083010203",
+		ptr:   new(multipleOptionalFields),
+		error: "rlp: input string too short for [3]uint8, decoding into (rlp.multipleOptionalFields).A",
+	},
+	{
+		// decode a nil ptr into a ptr that is not nil or not optional
+		input: "C20180",
+		ptr:   new(nonOptionalPtrField),
+		error: "rlp: input string too short for [3]uint8, decoding into (rlp.nonOptionalPtrField).B",
+	},
 	{
 		input: "C101",
 		ptr:   new(optionalPtrFieldNil),

rlp/encode_test.go

@@ -290,6 +290,10 @@ var encTests = []encTest{
 	{val: &optionalBigIntField{A: 1}, output: "C101"},
 	{val: &optionalPtrField{A: 1}, output: "C101"},
 	{val: &optionalPtrFieldNil{A: 1}, output: "C101"},
+	{val: &multipleOptionalFields{A: nil, B: nil}, output: "C0"},
+	{val: &multipleOptionalFields{A: &[3]byte{1, 2, 3}, B: &[3]byte{1, 2, 3}}, output: "C88301020383010203"},
+	{val: &multipleOptionalFields{A: nil, B: &[3]byte{1, 2, 3}}, output: "C58083010203"}, // encodes without error but decode will fail
+	{val: &nonOptionalPtrField{A: 1}, output: "C20180"},                                  // encodes without error but decode will fail
 
 	// nil
 	{val: (*uint)(nil), output: "80"},