should this be checked within in the if statement and then log an error and return?

if p.options.Schema != nil {
  if msg.Value == nil {
    p.log.WithError(err).Errorf("Schema encode message failed nil message")
    return
  }

}

Or should the ecoders be able to handle a nil value and return an error?

No, the assumption is that if value is null, a payload is already encoded.

Is that a safe assumption to make? What happens on the consumer side if that assumption does not hold?

I think we should at least add a comment explaining this because from looking at the code it's not obvious to me.

Sure - great call. Docs added.

A few more questions. I'm trying to figure out how to best solve this from an api perspective because if this goes in we are changing the api and will have to support it.

It seems like it's possible to pass a custom implementation of a schema is there a reason this can't solve the issue?

Why is app encoding the message before hand?

If the app is bypassing the internal encoder when producing does it need to bypass internal decoder on the consumer side as well?

I believe you can always bypass it on the consumer side if you don't call it and just read the Payload. You could implement a custom schema, maybe, but it would still be "hacky" for the use case I am proposing which is as a watermill adapter. Their interface requires payload to be a []byte, so we would have to set that to nil, then add the actual value to an untyped property.

If the intention is to bypass the schema encoding/decoding why set the schema on the producer and or topic?

I still want to take advantage of pushing schema to pulsar topic for schema validation