highlight-indent-guides VS lsp-mode

This one looks close. Also at the end of the readme there's a table comparing it to other alternatives.

Here is the issue: https://github.com/DarthFennec/highlight-indent-guides/issues/123

I meant to set it up but never wrote down what it was called and now I can't find it anymore. I'm not talking about this: https://github.com/DarthFennec/highlight-indent-guides and results for this (and the 5+ other packages that do this same thing) is all I can find when googling different variations of "emacs syntax coloring by indentation level" etc.

While older than Highlight-Indentation-for-Emacs, you can see also https://github.com/DarthFennec/highlight-indent-guides, the latter supports dynamic indent width detection (may not be important for JS, though).

I'm happy with https://github.com/DarthFennec/highlight-indent-guides and Emacs 28 (with native comp) but my files are not huge, max 400 lines generally.

Also for seeing indentation more clearly you could try something like highlight-indent-guides.

highlight-indent-guides has a mode like the one in the screenshot, but by default it doesn't show up in org-mode. I haven't tried to see what it would take to enable it there.

Before LSP, it was always annoying getting things setup. You want to get serious with a new language, spend a day configuring Emacs first. Or, fix your 3 year old config. Now it all pretty much just works! With native-comp its even better. Plus I'm using lot of modern features that I never did earlier, eg. renaming, automatically remove imports, see the inferred type in minibuffer.

Flycheck still makes it a bit slow. I think, one big missing piece is lack of multiple threads, which often makes few things a bit laggy. For example, if I'm reading a big C++ source code with indentation guides[1], even with native-comp it can lag a bit.

[1] https://github.com/DarthFennec/highlight-indent-guides

And there's also https://github.com/DarthFennec/highlight-indent-guides.

I also tried to the solutions suggested  and , but nothing worked. I moved the (setq lsp-keymap-...) line outside (and before) use-package. I also used :config (define-key lsp-load-map...) in my use-package block. But none of them worked.

Not sure how much this might help, but lsp-mode has lsp-yaml-select-buffer-schema and lsp-yaml-set-buffer-schema commands to pick schema from a list or set from a URI. Checking the source of them might give some hints about how the same could be implemented in eglot?

Beyond that you might as well embrace the suck and install autex with a language server: https://emacs-lsp.github.io/lsp-mode/

Smart completion these days is done primarily through LSP. eglot is fairly minimal but built-in as of 29, also available via GNU Elpa. lsp-mode is another option with more integrations and a bit more fleshed out.

lsp-mode: https://github.com/emacs-lsp/lsp-mode/issues/2080

Are you running emacs-29? It has numerous speed-ups compared to emacs-28 and older versions, many of them coded by Mattias Engdegård, e.g. commit def6fa4246. I have a fresh build of emacs-29 running on Linux and a new mac with an M1 CPU, and it's stupid fast. I don't use the native-comp feature. I rarely notice any hesitation or slowness. I don't use Elpy. I do use lsp mode.

Since you are doing code development, the first things to go for would be setting up your emacs packaging (installing use-package and melpa (use-package's documentation covers this) so you have more packages to choose from (do be careful to not just pick things willy nilly but research them a bit first)) and then setting up lsp-mode. lsp-mode lets you use LSP servers for the specific programming languages you work with in a somewhat unified fashion. You then need to install and setup the LSP servers for the languages you use, and possibly install language specific Emacs packages as support (note, Emacs has builtin functionality for many).

And first of all, I'm trying to understand, how is it connected to https://github.com/emacs-lsp/lsp-mode? I'm sure, that existed lsp implementations already parse source code. Why TreeSitter?