> That looks promising, but I have a feeling that vscode doesn't offer as much options to hook into the editor as emacs does.
Agreed on both counts.
But I don't think it's possible to get to Emacs' level of extensibility unless you adopt its philosophies - both legal and technical - from the outset.
The reason I say this is that Emacs isn't just extensible in Emacs Lisp, it's very extensively written in Emacs Lisp. More than that, the code behind all of the functions is a keystroke or three away. If I want to know what 'C-x C-s' does, it's possible to say 'C-h k C-x C-s' and see this:
> C-x C-s runs the command save-buffer (found in global-map), which is
an interactive compiled Lisp function in ‘files.el’.
There's more documentation besides, and pressing enter on 'files.el' then takes you to the source code for the save file function. This works for native C code too, provided you have the source installed.
This is very much like what you see in a Smalltalk image or a Lisp machine - the system is all 'of a kind', self-documenting, and fundamentally open by nature.
Web Browser JS environments have some of the interactivity here, but they miss out on the self-documenting part, the use of the extension language as an implementation language, and all the cross linking into the source. I'm not faulting them - these are expensive and time-consuming choices to take - and they are often at odds with the goals of writing a useful browser.
In that perspective, the work here is admirable in that it adds Lisp style scripting to VSCode, but it's destined to never get close to the sort of interactive extensibility and exploration you get in Emacs itself. I'm sure it's easy to run into the wall between the extension language and the implementation language itself.
Before this is taken as too critical, note that I don't mean it that way. This is just an observation about two different design choices based on two different sets of constraints that have led to two different outcomes. Note that both of these outcomes are good and useful points in the design space.