tree-sitter-fsharp

tree-sitter grammar for F# (still WIP) Based on the 4.1 F# language specification (Mostly, Appendix A) and the F# compiler parser

Getting started

First, run npm install to install the tree-sitter cli. Next, the grammar can be build using npm run build, or used to parse a file with npm run parse $file

Project structure

This project defined two parser:

• ./fsharp/grammar.jsfsharp grammar.
• ./fsharp_signature/grammar.js defines the grammar for signature files

In addition to the grammar.js files each parser depends on a common external scanner found at ./common/scanner.h. The external scanner is responsible for parsing newlines and comments and keeps track of indentation to open and close scopes.

each grammar starts with the file node at the beginning of the rules.

Adding to neovim

tree-sitter-fsharp isn't supported out-of-the box by nvim-treesitter. However, nvim-treesitter has instructions for how to manually add unsupported parsers.

For tree-sitter-fsharp, this involves three steps:

1. Update your Neovim config for nvim-treesitter to refer to tree-sitter-fsharp.
2. Run :TSInstall fsharp inside Neovim.
3. Copy the files from ./queries/ to the neovim config directory at$XDG_CONFIG_HOME/nvim/queries/fsharp/ - see the Adding queries section of the nvim-treesitter README.

The config you need is this (you can use a local path for url if you prefer):

local parser_config = require('nvim-treesitter.parsers').get_parser_configs()
parser_config.fsharp = {
  install_info = {
    url = 'https://github.com/ionide/tree-sitter-fsharp',
    branch = 'main',
    files = { 'src/scanner.c', 'src/parser.c' },
    location = "fsharp"
  },
  requires_generate_from_grammar = false,
  filetype = 'fsharp',
}

Development

The package.json defines some helpful targets for developing the grammar:

• npm run build rebuilds all parser.
• npm test runs all tests for both parsers.
• npm run parse $file run the fsharp parser on $file and outputs the parse tree.
• npm run debug $file run the fsharp parser on $file and prints debug information.

How to contribute

Clone the project and start playing around with it. If you find a code example which fails to parse, please reduce it to a minimal example and added to the corpus (fsharp/test/corpus/*.txt) as a test case.

For an introduction to developing tree-sitter parsers the official documentation is a good reference point.

PRs fleshing out the grammar or fixing bugs are welcome!