Roc for Visual Studio Code

Official Roc language support, powered by the language server built into the roc compiler.

Features

Syntax highlighting, including Roc code blocks in doc comments and Markdown files
Diagnostics as you type
Formatting (format on save is on by default for Roc files)
Hover with inferred types, go to definition, find references, document highlights
Completion, rename, document symbols, folding and selection ranges
Inlay hints for inferred types
Code action: annotate a binding with its inferred type
Semantic highlighting
Roc: Run File and Roc: Test File from the editor title bar, and a roc task type

Thanks

Thanks to Luke Boswell, whose roc-vscode showed how to test the packaged VSIX, and inspired the language feature, editing and server lifecycle tests here.

Getting `roc`

The extension uses the first roc it finds:

the roc.path setting
the nightly installed by this extension
roc on your PATH

If there is none, it offers to download the latest nightly from roc-lang/nightlies. Downloads are checked against the sha256 digest GitHub publishes for the release asset. You can also run Roc: Install or Update Nightly at any time. While you use the nightly installed by the extension, it checks once a week whether a newer one exists and asks before updating; turn this off with roc.nightly.checkForUpdates.

Workspace trust

Checking Roc code can download packages and run compile-time Roc code, so the language server only runs in trusted workspaces. In restricted mode the extension still highlights, formats (with roc fmt, which only parses) and folds. Trusting the workspace starts the language server.

In restricted mode, roc.path and roc.server.args are only read from your user settings, so a repository can't choose which program runs.

Settings

Setting	Default	Description
`roc.path`	`""`	Path to the `roc` executable. `~` and `${userHome}` are expanded.
`roc.server.args`	`["experimental-lsp"]`	Arguments that start the language server.
`roc.server.debugFlags`	`[]`	Any of `--debug-transport`, `--debug-build`, `--debug-syntax`, `--debug-server`. The log file path appears in the Roc output. Transport logs contain your source code.
`roc.nightly.checkForUpdates`	`true`	Weekly update check for the nightly installed by the extension.
`roc.trace.server`	`"off"`	Log language server messages to the Roc output.

Tasks

// .vscode/tasks.json
{
	"version": "2.0.0",
	"tasks": [
		{ "type": "roc", "command": "test", "file": "main.roc", "label": "roc test" },
		{ "type": "roc", "command": "run", "file": "main.roc", "args": ["--", "arg1"], "label": "roc run" }
	]
}

Development

npm ci                    # install pinned dependencies (install scripts are disabled in .npmrc)
npm run check             # typecheck
npm test                  # unit tests and grammar snapshot tests
npm run test:nightly      # install the nightly pinned in test/roc-nightly.txt into .vscode-test/roc with the extension's installer
ROC_PATH=/path/to/roc npm run test:integration  # package, install and test the VSIX in a real VS Code
npm run package           # build roc-<version>.vsix

The integration tests install the packaged VSIX into a fresh VS Code profile, so packaging mistakes show up. They run once in a trusted and once in a restricted workspace, and check language features, editing, and restarting and stopping the language server. ROC_VSIX tests an existing VSIX instead of packaging one, VSCODE_VERSION picks the VS Code build, and ROC_TEST_GREP runs only the tests whose name contains it. CI also checks the VSIX contents against test/vsix-files.txt.

Press F5 to try changes in a new VS Code window.

The TextMate grammar lives in syntaxes/roc.tmLanguage.json. After changing it, run npm run test:grammar -- --update and review the snapshot diff in test/grammar/fixtures/.

Dependencies are deliberately few: vscode-languageclient at runtime, and Microsoft's or esbuild's own tooling for development. New versions are only adopted once they have been published for at least two weeks.

Roc

Roc lang