failing test for backwards compatibility with omitempty

[ebuchman]

Failing test illustrating unexpected behaviour with omitempty and binary encoding

[odeke-em]

@ebuchman the test seems to be failing with
reflect_test.go:842: Varint overflow
which doesn't seem to have a dependence on if we use ",omitempty" or not, please see

diff --git a/reflect_test.go b/reflect_test.go
index 965eb06..919292a 100644
--- a/reflect_test.go
+++ b/reflect_test.go
@@ -812,7 +812,7 @@ type MyStruct1 struct {
 
 type MyStruct2 struct {
 	A string `json:"a"`
-	B string `json:"b,omitempty"`
+	B string `json:"b"`
 }
 
 func TestReadOmitEmptyJSON(t *testing.T) {
@@ -835,6 +835,8 @@ func TestReadOmitEmptyBinary(t *testing.T) {
 	s2 := new(MyStruct2)
 
 	b := BinaryBytes(s)
+	bs := BinaryBytes(&MyStruct2{A: "hi"})
+	t.Logf("\nb: %x\nbs:%x\n", b, bs)
 	err := ReadBinaryBytes(b, s2)
 	if err != nil {
 		t.Fatal(err)

which fails the same, with

--- FAIL: TestReadOmitEmptyBinary (0.00s)
	reflect_test.go:839: 
		b: 0101026869
		bs:010102686900
	reflect_test.go:842: Varint overflow
FAIL
exit status 1
FAIL	github.com/tendermint/go-wire	0.010s

[ebuchman]

Yep so this is expected behaviour of go-wire - it's not extensible like JSON or protobuf are. We should document that better.