semantic-source VS diffsitter

ah, easy. it's because support has not been added into https://github.com/github/semantic which is the tech that powers the GitHub UI. Adding support is pretty easy/mainly glue code [1] that imports the tree sitter API.

[1] https://github.com/github/semantic/blob/793a876ae45d38a6bd17...

I believe they use semantic (Haskell program that uses tree-sitter) for navigation: https://github.com/github/semantic

So the answer may be that semantic does not yet have support for the language in question.

GitHub used Haskell for implementing Semantic, a command-line tool for parsing, analyzing, and comparing source code.

As far as engineering effort, you can read this GitHub comment for an overview of where we’d like to take the project in the future. The tl;dr here is that the open sum type view of the world made it very concise to fold over syntax trees (since such a view of data is ultimately unityped, recursion schemes Just Work), but the tradeoff thus associated—namely, that you have to parse a concrete syntax tree into an open-sum view (a complicated and painful-to-read process), that you can never really be sure how a given syntax tree is shaped, and that the types don’t help you nearly as much as they could—proved to be too onerous to deal with. Going forward, we’re generating syntax types from the AST once per target language, and working on an abstraction (probably via this generated code; I made five separate efforts at using Generics for this, and failed every time) that recovers at least some of the convenience of recursion schemes. It turns out that recursion schemes over a mutually recursive syntax tree—as pretty much every language’s syntax trees are, in practice—are pretty much an unsolved problem, especially when extended to languages like TypeScript, which have hundreds of different syntax nodes.

I'm just curious. It seems there hasn't been much activity in https://github.com/github/semantic Is GitHub still using semantic it to power some code navigation features? Has it been abandoned or is there some successor project that has taken its place? Is there any writeup / lessons learned about this project?

is this from Github semantic (https://github.com/github/semantic)?

Seems very suspicious since it’s the same goal using the same technologies. The latest commit is 4mo ago but i assume they have a closed-source version they’ve been working on.

Meanwhile their Tree-Sitter-based semantic parser[1] looks abandoned. There is even rotting for years pull request[2] adding support of the same stack graphs into it.

[1] https://github.com/github/semantic

[2] https://github.com/github/semantic/pull/535

Does anyone here have experience with tree-sitter? If you aren't familiar, tree-sitter is a parser generator tool that builds parsers to use with an incremental parsing library. It's what's responsible for AST parsing on GitHub, for instance.

For git diff's I've been using https://github.com/afnanenayet/diffsitter

One more tree-sitter based diffing tool - diffsitter

https://github.com/afnanenayet/diffsitter

Several threads here point to difftastic: https://github.com/Wilfred/difftastic

I know a lot of people who have a lot of hope for diffsitter (or something like it): https://github.com/afnanenayet/diffsitter

Personally, I think the reason most "good" semantic diff tools are proprietary is that they are huge amounts of effort that are mostly "hacks" and "heuristics" bandaged together in ways that people don't want to let out how the sausage was made.

But I also "general, language agnostic AST-based semantic diff" is a mountain peak we cannot reach (probably ever), and I believe my experiments found an interesting local maxima that people are maybe sleeping on (lexer-based diffs rather than parser-based diffs): https://github.com/WorldMaker/tokdiff

https://github.com/afnanenayet/diffsitter there are quiet a few projects such as this one, attempting to solve the issue. :)

There’s an interesting project in the semantic diff/merge space that I have been keeping an eye out for https://github.com/afnanenayet/diffsitter

I have never used any of them, but it look like tree-sitter based diff tools are exactly what you are searching for (like difftastic, gumtree or diffsitter).

Counterpoint: a quick google reveals diffsitter: https://github.com/afnanenayet/diffsitter

The output could be a lot more compact, it could do better at adding context (in the same way https://github.com/romgrk/nvim-treesitter-context does, etc), so if you're interested in this it's really within reach, go help out.

I believe Unison is the only attempt to do this at a programming language/environment level.

For Git diffs, there is Diffsitter, which uses Tree Sitter to generate semantic diffs of code files: https://github.com/afnanenayet/diffsitter

I have not used it, but it is high on my todo list.

I think everyone may be interested in: https://github.com/afnanenayet/diffsitter

Github having an option to have their PR GUI use an AST diff like this could be a fun and useful option.

Looks great, I'll try it! FYI, there is a very similar project called diffsitter https://github.com/afnanenayet/diffsitter