Transparent encoding

[magik6k]

This PR adds support for 'transparent' encoding, either in structs with cborgen:"transparent" tag (which can be used with other tags), or by just defining a newtype that isn't a struct

type IntAlias int64

type IntArray struct {
	Ints []int64 `cborgen:"transparent"`
}
type IntAliasArray struct {
	Ints []IntAlias `cborgen:"transparent"`
}

type IntArrayNewType []int64

type IntArrayAliasNewType []IntAlias

type MapTransparentType map[string]string

Opinions this is based on:

• Transparent encoders can only be generated in tuple mode
  • Map mode entries have name prefixes, so technically tuple mode makes more sense
• Only one transparent entry in structs with transparent entries
  • Technically we could allow multiple entries, in any case we're just stripping the array header, but that will make things like encoding structs with multiple transparent entries in maps/arrays much more complicated, so just one transparent entry for now

[Stebalien]

Do we need the version that supports the transparent tag? Personally:

1. I'd prefer to just stick with newtypes.
2. I'm not a huge fan of using a tag here, I'd consider introducing a WriteTransparentEncodersToFile. On the other hand, it is nice having this information in the file itself.

[Stebalien]

(basically, I'd consider just sticking with newtypes to avoid the bikeshed)

[rvagg]

Would be nice to see tests with pre-recorded forms rather than just roundtrips. I'd come up with some but I'm only on my phone at the moment. If you npm install cborg -g then you can do things like cborg json2hex '["foo",[1,2,3],true]'.

[magik6k]

Do we need the version that supports the transparent tag?

I’d say yes, this is the only way that makes it possible to do things like set array size limits and nil slice handling, which will inevitably be useful

[Stebalien]

Ah, good point.

[Stebalien]

This looks correct. I'd much prefer to find a way to split this out into multiple functions as I think someone will trip over this eventually, but I'm not the one writing the code so I'm not sure how much work that would be.

[rvagg]

nice

[whyrusleeping]

Neat, seems useful