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I've been following tree sitter for a while, as I find the tech super cool and can't wait to see more practical applications.

One thing (among many others) that I've found really promising about Dark is its editor. See the hands-on video on their homepage for a demo: https://darklang.com/

It mostly feels like you're just typing text like in any regular text editor, but your inputs are actually manipulating the AST directly, and the editor itself ensures that your inputs can never result in an invalid program (i.e. there's no such thing as making a syntax error in Dark). It's inspired by tooling in the lisp world like Paredit and Parinfer, but Dark itself doesn't have to _look_ like a lisp because the structure of the AST is maintained by the editor itself instead of by users manually inserting and removing parens. It's an ingenious way to get most of the productivity benefits of a lisp-style syntax and all the structural editing tooling that comes with it, without intimidating new-comers with the super foreign looking parens infested syntax lisps are infamous for.

The other day I was actually briefly looking into whether or not it could be possible to replicate something like this in Atom using tree-sitter for some mainstream language like JS, but ended up getting blocked by the fact that Atom doesn't seem to offer an API for plugins to block/replace user input. This is probably for the best, given all the horrible ways this could be abused, but it does mean if I wanted to explore the idea further I'd probably have to either fork Atom to experiment with the idea or build something up from scratch, which is a pretty daunting undertaking given how deceptively complex modern editors can get these days.

But maybe I'm missing a different way to accomplish this in Atom with its existing APIs? Or does anyone know if VSCode's extension APIs can support this use case? I realize I've probably barely scratched the surface given how little time I've spent on it so far.






I really don't think it's inspired by Parinfer. It's likely based on the theory of structural editing and AST projections first popularized by JetBrains' CEO and available for experimentation in the open source project MPS. An end to end application of this theory is commonly referred to as a language workbench.

Papers: https://confluence.jetbrains.com/display/MPS/MPS+publication...

Language workbenches: https://www.martinfowler.com/articles/languageWorkbench.html

Nice intro to structural editing:https://medium.com/@mikhail.barash.mikbar/looking-at-code-th... (also mentions scratch)


> It mostly feels like you're just typing text like in any regular text editor, but your inputs are actually manipulating the AST directly, and the editor itself ensures that your inputs can never result in an invalid program (i.e. there's no such thing as making a syntax error in Dark).

The basic idea has been around for a while.

Here's something from the 80's: Alice Pascal https://www.templetons.com/brad/alice.html

> One of the first projects I did after forming Looking Glass Software Limited was a syntax-directed programming environment called Alice: The Personal Pascal.

> Syntax-directed editors are somewhat controversial, however I think they are quite good for people learning programming, and Alice was written first to be used in education in the school systems of Ontario. Our first sale was a contract to develop it for the Ministry of Education there.


> The other day I was actually briefly looking into whether or not it could be possible to replicate something like this in Atom using tree-sitter for some mainstream language like JS,

already being done as part of CodeMirror v6:

https://marijnhaverbeke.nl/blog/lezer.html

https://github.com/lezer-parser/




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