Language servers are the new big deal in editor and IDE development:
https://langserver.org/

It would be cool to have a ConTeXt one for autocompletion (for ConTeXt:
command names, \cite IDs, labels, named parameters, …), go-to-definition,
hover information (docs about a command) and so on.
The way it works is that you have a server process that is the source of
truth for all this information, and the editor passes requests to it.
The editor tells the server when it opens/closes files and when the user
requests something of the above.

The way I’d implement it in ConTeXt is to keep a list of open ConTeXt
projects in the server (obtained by following \include, \component,
\product, \environment, \project).
Now my questions begin:

   1. Then I’d make context load the project without compiling it to a PDF
   but make it execute some Lua (how do I do this?)
   2. I’d need a way to get all available commands with their signatures
   into Lua. I assume this is done here, but how?
   http://www.pragma-ade.nl/general/qrcs/setup-en.pdf
   3. Optimally, for hover information and completion, I’d want some
   help/doc text for each command that has some. Is there a way to get it?
   4. Optimally, for label autocompletion, I’d also like a list of defined
   labels. Since I played around with bibliographies I already know how to
   query the bibliography DB from Lua.
   5. Optimally I’d also want some parse tree of each document, but I
   assume the way macros work, this doesn’t exist? This would make things
   easier that I’d otherwise have to (imperfectly) parse out of the document
   (due to things like catcode changes, but I guess I can pretend they don’t
   exist and \unprotect is always on)
   6. Optimally, for go-to-definition, I’d also want a list of files
   ConTeXt loaded so I can find definitions in it.

Can anyone help me, especially with 1-2? To get me started, it would be
great to have an example script and a command line to invoke it, which
makes ConTeXt load a main tex file, execute some Lua, and exit without
creating a document or writing anything else to the channel Lua writes to
(stdout?).

Best, Philipp