The REPL has spoilt me. Working with languages without a powerful REPL, even ones with a shell like JS/Python/Lua/Ruby feels like a regression comparable to moving from zsh to windows cmd.
There really, really should be a standard protocol for communicating with a REPL in a running program like there is for IDEs in the Language Server Protocol. Maybe that way the concept would become more mainstream if you could just take any REPL client and walk up to a program with a REPL server and interactively explore its state. The closest thing to said protocol is nREPL which is what Clojure uses, but there are a lot of nonstandard extensions to the protocol for edge case features only applicable to Clojure, so almost every client assumes you're using Clojure and it greatly reduces the viability of using it for Lua or other languages. It doesn't have the backing of something like Microsoft either, I guess because this REPL thing lives in its own world with the Clojure userbase.
I opened an issue on Clojure's REPL integration with Emacs for supporting more languages[1]. I wanted to take advantage of the effort spent on Clojure's client side tooling for things like the command prompt and state visualiser but apply them to at least Lua and allow others to add their own support for other languages. It would be a really big effort but I've already seen the value of it by integrating a REPL with projects written in Lua. As you said I can't ever imagine using a dynamic language without one again.
Actually when I think about it the thing I made probably isn't a "REPL" in the Clojure sense since all it has is a command line and module hotloading; there is no namespace support and the command line evaluation does not happen in the context of the program, but you can basically call a function that gives you the entire global state of the game to mess with and see changes instantly. Maybe that's a better approach than having global state shared between both as Lua has no namespace support built-in, and I don't want to hack it on to keep things simple.
Here is the drawing code for the REPL in-game.
https://github.com/Ruin0x11/OpenNefia/blob/master/src/api/gu...
Here is the server which listens for commands using a custom protocol. I want to use nREPL at some point but that requires merging some changes into external projects with the client side tooling.
https://github.com/Ruin0x11/OpenNefia/blob/master/src/intern...
Here is the code which handles hotloading. It's complicated but I had to write the system so that it also handles sandboxing external mods and hooks into Lua's module management, running special checks to see if the loaded code is not part of the base game. You can probably get away with the version in lume if you don't need as much. But the point is that this is what ultimately allows changing files and seeing the changes instantly without restarting the program.
https://github.com/Ruin0x11/OpenNefia/blob/master/src/intern...
https://github.com/rxi/lume/blob/98847e7812cf28d3d64b289b03f...
Here is the integration with Emacs.
https://github.com/Ruin0x11/OpenNefia/blob/master/editor/ema...
Genuinely never got how people use zsh. It's the slowest and clunkiest shell I've ever witnessed it's fucking slower than most electron gui software.
`esc, esc` to prefix the line with `sudo`, better tab completion (both the navigatable UI with arrow keys, along with the intelligent tab completion (I type in "./llo" and it finds the file "./helloworld.sh")), combined with the massive amounts of customization and modules you can install makes it a shell killer. The only shell I've found that I like more is Windows' Powershell, however that's mostly because I __love__ the Powershell language and syntax.
However I will admit that almost all of what I just complimented is part of oh-my-zsh, which is a community add-on for zsh which makes the experience so much nicer. In my time I've used bash, csh, pwsh and zsh and if I could, I'd always use zsh for termanal interactivity and pwsh (Powershell on Linux) for scripts.
I don't use my shell for intensive computing so I've personally never perceived any slowness or clunkiness.
In a Python shell, for example, you can't redefine an existing function and see how it affects your system.