for adding support for JDocumentRenderer[doc-type][rendered-type]. How about now providing a standard set of JDocumentJson renderers? Should we?

I have tested this item successfully on aa7c947

As per test instructions, tested that Joomla itself functions the same

@izharaazmi something like that won't be part of this PR. As long as people are extending the right classes (which we have checks for) then it's down to them to provide an implementation. In the future we could investigate some sort of interface. But it's likely going to be something JDocumentRenderer already supports anyhow

Yeah, I understand that that can't be part of this PR. I was asking for the additional prospects. I think we can provide a full fledged structured rendering similar to that of html renderers, like response code, messages, body, redirects, callbacks, etc or whatever we can figure out when into it.

This can give us a well defined format for Joomla based JSON APIs as well. Same can be done for XML rendering for XML APIs.

I understand that this is not the part of Joomla project scope right now. But I wonder, what if?

Btw, JDocumentJSON right now appears to be just a barebone (sorry! I may be wrong here). It renders the output with Content-Disposition: attachment anyway, which usually is not helpful always.
However, these can be discussed later in case we actually decide to work on this.

Exactly. There's definitely a lot of work to do with JDocument. I see this as the start of getting a lot of these issues fixed up

JDocument and its subclasses aren't a proper request/response structure, nor even responsible for building the response. It is at best a page rendering system; all of the response data is handled as part of the JApplicationWeb API. JDocument does have a couple of calls into the application to set some response data based on the format, but that's the extent of what it's capable of at the moment.

I have tested this item successfully on aa7c947

I have been working with this patch, it works OK.