el-patch VS prism.el

I also tweak that function for similar reasons. I personally use el-patch for that: https://github.com/radian-software/el-patch. This way, at least we can ensure our redefinition does not get out of step with the original. Anyway, I also find it hard to do otherwise, because we need the match data at the correct point, so just advising the function becomes tricky.

Check out el-patch--if I understand what you're trying to do, it's designed for exactly this use case!

Yeah and even in personal config one could use el-patch[1], to make monkeypatching future proof.

[1] https://github.com/raxod502/el-patch

Speaking for myself, I have a lot of (use-package some-package :config (defun some-package-function-I-want-to-override (...) ...)) in my config file, which works well enough to override package definitions. In case you don't use use-package, then (eval-after-load 'some-package '(defun ...)) also works. I also use a lot of advice. Although I don't use it, https://github.com/raxod502/el-patch provides a more structured approach to patching definitions using a novel sexpy patch format.

Heh, seriously, though, it's not necessary to use a rainbow of colors. You can use any number of colors and rotate through them. For example, this uses just 3 colors, gradually desaturating them as the depth increases. Since each color is easily distinguished from the other 2, it makes code very readable: https://github.com/alphapapa/prism.el/raw/master/images/parens-0.5.png

If you can use tree-sitter, that's obviously a good choice. Alternatively, you can see how I implemented https://github.com/alphapapa/prism.el, which isn't regexp-based, using Emacs's built-in syntax parsing instead.

I did some experimenting with supporting XML directly in https://github.com/alphapapa/prism.el/issues/16. It seems that it's not easily done with existing Emacs SGML-related functions, but I'm guessing that tree-sitter will help a lot in Emacs 29.

It's not exactly what you asked for, but you may also find this useful: https://github.com/alphapapa/prism.el It can highlight parens distinctly too.

As examples, I can recommend code in https://github.com/alphapapa/highlight-function-calls (simple) and https://github.com/alphapapa/prism.el (more complex).

There is also the package prism.el.

The best advice I can offer is to carefully and repeatedly study the Elisp manual section on font-lock, and to model on the source code of a similar project. The most I've done with it is in https://github.com/alphapapa/prism.el

There is one for emacs. Could be good inspo if someone wanted to make a VSCode version.

https://github.com/alphapapa/prism.el

You might be interested in https://github.com/alphapapa/prism.el