Specify msgpack decode option to return strings for appropriate types

[paddybyers]

We need to specify RawToString: true: https://github.com/ugorji/go/blob/master/codec/msgpack.go#L521

[gernest]

Please make sure the tests are passing. I see a nasty panic on the ci logs.

panic: interface conversion: interface {} is string, not []uint8 [recovered]
	panic: interface conversion: interface {} is string, not []uint8

Also

    // RawToString controls how raw bytes are decoded into a nil interface{}.
    RawToString bool

Now we really dont want this behavior. I considered this before and decided it should not be used because strings in go are utf-8 meaning this will mangle any raw bytes encoded in msgpack.

[paddybyers]

Now we really dont want this behavior. I considered this before and decided it should not be used because strings in go are utf-8 meaning this will mangle any raw bytes encoded in msgpack.

OK, but I think you're misreading the intent of the option. In older msgpack versions there was no distinction between binary and string values, and they were labelled as a single "raw" type. Then the spec was changed to introduce separate string and binary types, and there was a migration path where the legacy "raw" types could be interpreted as either a string or binary value. See https://github.com/msgpack/msgpack/blob/master/spec.md#upgrading-messagepack-specification

This option in the library affects the decoding of various opcode ranges, particularly the opcodes that were historically raw types. The opcode for the "client1" member in the message data was 0xa6, which is in the FixStr range (see https://github.com/ugorji/go/blob/master/codec/msgpack.go#L38) - our msgpack encoder in the Ably system correctly uses this opcode for short fixed-length strings, so we need these decoded as strings. The RawToString option controls this - see https://github.com/ugorji/go/blob/master/codec/msgpack.go#L520. It does not mean that every binary type is decoded to string type; the binary opcodes are all unconditionally decoded to bytes - see https://github.com/ugorji/go/blob/master/codec/msgpack.go#L528.

[paddybyers]

Please make sure the tests are passing. I see a nasty panic on the ci logs.

panic: interface conversion: interface {} is string, not []uint8 [recovered]
panic: interface conversion: interface {} is string, not []uint8

Agreed, I need to look at this.

[paddybyers]

I see a nasty panic on the ci logs.

panic: interface conversion: interface {} is string, not []uint8 [recovered]
panic: interface conversion: interface {} is string, not []uint8

See eb6dba9: this was an error in the test, incorrectly expecting some members of decoded messages to have []byte type.

[gernest]

LGTM