tree-sitter-fsharp

F# grammars for tree-sitter, packaged for Node.js.

The package ships two parsers:

Export	Grammar	File types
fsharp	implementation files	.fs, .fsx
signature	signature files	.fsi

Installation

npm install tree-sitter-fsharp tree-sitter

tree-sitter (the Node runtime, ^0.25.0) is an optional peer dependency: install it alongside this package to parse with the native bindings.

Prebuilt binaries are published for the common platforms and picked up automatically by node-gyp-build. On any other platform the parsers are compiled from the bundled C sources at install time, which requires a C compiler and the usual node-gyp toolchain.

Usage

const Parser = require("tree-sitter");
const { fsharp, signature } = require("tree-sitter-fsharp");

const parser = new Parser();
parser.setLanguage(fsharp);

const tree = parser.parse("let x = 1\n");
console.log(tree.rootNode.toString());

Signature files need the other grammar — it is a separate parser, not a mode of the first:

parser.setLanguage(signature);
const tree = parser.parse("module M\nval x : int\n");

Both exports carry a nodeTypeInfo property holding the parsed node-types.json for that grammar, and TypeScript declarations are included.

Queries

Highlight, injection, locals and tags queries ship inside the package. Resolve them relative to the package root:

const fs = require("node:fs");
const path = require("node:path");

const root = path.join(path.dirname(require.resolve("tree-sitter-fsharp")), "..", "..");

const highlights = fs.readFileSync(path.join(root, "queries", "highlights.scm"), "utf8");
const sigHighlights = fs.readFileSync(
  path.join(root, "fsharp_signature", "queries", "highlights.scm"),
  "utf8",
);

queries/ holds highlights.scm, indents.scm, injections.scm, locals.scm and tags.scm for the implementation grammar; fsharp_signature/queries/ holds highlights.scm and tags.scm for the signature grammar.

WebAssembly

The published tarball also contains tree-sitter-fsharp.wasm and tree-sitter-fsharp_signature.wasm at the package root, for use with web-tree-sitter. Parser.init() must resolve before anything else:

const { Parser, Language } = require("web-tree-sitter");

await Parser.init();
const fsharp = await Language.load(
  require.resolve("tree-sitter-fsharp/tree-sitter-fsharp.wasm"),
);

const parser = new Parser();
parser.setLanguage(fsharp);

In a browser bundle, serve the two .wasm files as static assets and pass their URLs to Language.load instead of a filesystem path.

Contributing and grammar development

Grammar sources, the test corpus and the development workflow live in the repository: see the main README and AGENTS.md. Bug reports for mis-parsed F# code are welcome — reduce the snippet to a minimal example and open an issue or PR.

License

MIT — see LICENSE.