Support encoding.BinaryMarshaler/Unmarshaler

[niemeyer]

Support the standard marshaling/unmarshaling interfaces from the encoding package:

• BinaryMarshaler
• BinaryUnmarshaler

[advance512]

Is this considerably different from the support that already exists for TextMarshaler/TextUnmarshaler?

What use cases does this have?

[niemeyer]

This means supporting types that implement that interface. The support for types that implement a different interface won't make that work.

[lrewega]

This is specifically useful for url.URL due to it's inability to implement encoding.TextUnmarshaler until Go 2:

• golang/go@6595709
• all: decide what can implement TextMarshaler/TextUnmarshaler golang/go#10275 (comment)

I might take a crack at this.

[niemeyer]

The same problem reported as a breakage there also looks like an issue for yaml.

It's a bit of an awkward choice to trust on the binary encoding of the type to present a nice textual representation. I wonder if it will backfire in other cases, where we'd otherwise get a pleasant representation of the fields, and now get some unreadable binary blob.

We might support BinaryMarshaler/Unmarshaler in v3 before it's final, but we'll need to first have a look to understand what the most common conventions are around it.

[mfridman]

To echo @lrewega, this would be very useful for url.URL support.

@niemeyer v3 landed a few months ago, what are your thoughts on the issue?

[mfridman]

ping @niemeyer . This has been a long outstanding issue, what are your thoughts on adding support for this?

Any reason not to add this?