Hmm. The link to GM says:

Ooops!

Sorry friend, looks like this challenge is no longer available.

My title: " Never say IMPOSSIBLE with IRIS " 

I fully support you.
Out of tradition, there is a tendency to implement already existing solutions though  better
and well-positioned on the markets. 
@Dmitry Maslennikov :
- you might remember times when even a webserver was written inside Caché
- or various text editors, source manager packages, and ..., and ... and ...
JUST because it was possible.

Decades back you had your globals and your language and not even an OS below.
But this was in previous millenium. This time is definitely over.
 

I missed this during a migration from Caché to IRIS.
There were roughly 1500 routines and ~2000 classes. grown over >15 years.
The point was to find out dependencies and estimate the impact of changes.
 

A cross-reference for external Classmethods and/or routines within:

• a routine
• a class
• a package of classes
• a package of routines

this

The key issue I see is: Is there a Related XML schema available.
If YES:
- you can generate a package with the existing tools
- import the file with %XML.Reader
- do an %JSON... export
The XML schema is necessary because straight XML is just TEXT with no datatypes
while JSON has data types. For XML the type of data is documented in XML Schema.

If NO:
You may call any of the public available XML to JSON converters.
They may guess rather easy for numerics vs. strings in most cases.
But detecting Boolean (true /false ) vs. Integer is somewhat mysterious to me.

My personal opinion: re-inventing this wheel is not worth the effort.
Writing an adapter makes sense 
 

Thank you @Nigel Salm !

The buzzword "language"  distracted me.
In IRIS our good old ENSEMBLE was renamed to Interoperability and is there by default.

​​​​​@Heloisa Ramalho you should know it best and could give  a native explanation

Thanks!  

In DC ANALYTICS / Authors what do these column headers stand for?

• Comment Rating
• Post Rating
• VPP Context
• VPP Absolute

For Rating I'd expect Votes ? 
But VPP ? 

   docs sounds boring

@Dmitry Maslennikov 
Is this also supported by VSCode?

I removed my example on PuTTY. 
It worked by mistake as the local firewall was switched off

If setup correctly it basically works as described by @Alexey Maslov 
and you need to log in separately on the server,
 

Correct.
After 20 years working with CSP since day 2.5 I just don't feel like discussing and explaining CSP internals anymore and argue against obviously wrong statements. 
There is enough public detailed documentation around .

Set Property Parameter %JSONNULL = 1

  Property Code As %String(%JSONNULL = 1);

Code = ""  >>> "Code":null
Code =$c(0)  >>> "Code":""

@Rob Tweed , @Dmitry Maslennikov 
Congratulations to you both! That's real ENGINEERING !    
 

Just post the class. 

JUST Great ! 
I like it.