Convert json-xml module to use JSONiq items

[Chris Hillery]

The old "converters/json" module has been updated to be named "json-xml". However it still behaves the same way - converts between a couple different XDM forms (JsonML, Snelson) and JSON text. It would make more sense now for the inputs and outputs to be json-item()s instead:

declare function jx:xml-to-json($xml as item()*, $options as object()) as json-item()*

declare function jx:json-to-xml($json as json-item()*, $options as object()) as element(*,xs:untyped)*

(I'm not sure whether those should be json-item()* or just json-item() .)

[Chris Hillery (ceejatec)]

As discussed on the conf call, assigning to Paul to get his opinion on how large a task this would be. He would be the most reasonable person to implement this as well. Subscribing Ghislain so he can register his opinion on the exact API.

[Paul J. Lucas (paul-lucas)]

As I requested on the conf. call, please explain WHY it makes more sense now. What use cases does the proposed change make simpler? What cases does it make harder? If I already have an xs:string, how would I use json-to-xml() with the proposed change?

[Chris Hillery (ceejatec)]

> please explain WHY it makes more sense now.

Because we have JSONiq now, and it's become a central part of the Zorba identity. It's weird (IMHO) to have a module in Zorba that deals with JSON only as strings, rather than data model instances.

> What use cases does the proposed change make simpler?

Any that involve getting JSON back from something (such as the new JSONiq-based http-client module, or the database drivers) and wanting to convert that to JsonML, etc. There are a great deal more ways of getting JSON data model instances than there are of getting JSON strings.

> What cases does it make harder?

If we leave the existing functionality in place (which is what I originally suggested), then nothing would become harder. The trick there is coming up with reasonable function names, since you can't really overload a single function name.

If we eliminate the JSON string functionality entirely (which is what Ghislain suggested), then any use case where you actually have only a JSON string would have one additional step. Also, it's possible that doing this might break streamability (does the module support that currently?).

> If I already have an xs:string, how would I use json-to-xml() with the proposed change?

jx:json-to-xml( jn:parse-json( $mystring ) )

[Paul J. Lucas (paul-lucas)]

Well, I could (for now) rename the string versions to include "string" in their names:

    json-string-to-xml()
    xml-to-json-string()

[Paul J. Lucas (paul-lucas)]

FYI: This is a LOT of work. About 25% done.