roc/crates/language_server

roc_language_server

This is a basic language server for Roc.

Support for the following LSP features are provided:

• Inline diagnostics
• Hover to view type of value
• Go-to-definition
  • Example

    https://github.com/ayazhafiz/roc/assets/20735482/23a57d06-5b70-46f2-b0c4-5836eaec669b

  • Note that go-to-definition for the builtins does not yet work.

  • Go-to-definition for abilities resolves to their specialization, if one exists.

    • Example

      https://github.com/ayazhafiz/roc/assets/20735482/1ba98bf9-518b-4c47-b606-a6ce6767566f

• Formatting Roc files on save
  • Example

    https://github.com/ayazhafiz/roc/assets/20735482/fbbe4bc1-64af-4c7d-b633-d7761906df11

Semantic highlighting will be added soon. Additional features require changes to the compiler infrastructure that are not yet available.

Note that the language server is a bit naïve:

• If you make a change in a dependency, you'll also need to make a change in the dependents' files for the changes to be picked up.
• The language server will only operate on changes on save, auto-saving is recommended.

Installing

The roc_language_server binary is included with the nightly releases. We recommend using the same version of roc and roc_language_server.

Building from source

Follow the building from source instructions for roc. Then run:

# do `nix develop` first if you're using nix!
cargo build --bin roc_language_server --release

This will give you the language server binary at:

target/release/roc_language_server

Configuring in your editor

Please follow your editor's language server implementation's documentation to see how custom language servers should be configured.

coc.nvim

Add the following to your coc JSON configuration file:

{
  "languageserver": {
    "roc": {
      "command": "<path to binary folder>/roc_language_server",
      "filetypes": ["roc"]
    }
  }
}

If you're using coc.nvim and want to use the configuration above, be sure to also instruct your vim that *.roc files have roc filetype.

nvim-lspconfig

Add the following to your lspconfig setup:

local lspconfig = require('lspconfig')
lspconfig.roc_ls.setup()

Make sure that the roc binary is on your PATH. Further instructions on how to setup nvim-lspconfig can be found in their docs.

Debug

If you want to debug the server, use debug_server.sh instead of the direct binary.

If you would like to enable debug logging set the ROCLS_LOG environment variable to debug or trace for even more logs. eg: ROCLS_LOG=debug

Testing

Tests use expect-test, which is a snapshot/expect testing framework. If a change is made that requires updating the expect tests run cargo test confirm that the diff is correct, then run UPDATE_EXPECT=1 cargo test to update the contents of the files with the new output.

Config

You can set the environment variables below to control the operation of the language.

ROCLS_DEBOUNCE_MS: Sets the amount of time to delay starting analysis of the document when a change comes in. This prevents starting pointless analysis while you are typing normally. Default: 100

ROCLS_LATEST_DOC_TIMEOUT_MS: Sets the timeout for waiting for an analysis of the latest document to be complete. If a request is sent that needs the latest version of the document to be analyzed, then it will wait up to this duration before just giving up. Default: 5000