rescript-vscode

The official VSCode plugin for ReScript.

Prerequisite

You must have rescript >=9.1 or bs-platform >=8.3.3 installed locally in your project, through the usual npm installation. Older versions are not guaranteed to work.

Recommendation

Our highlighting works well with most popular VSCode themes, such as:

Dark+ (default dark), Light+ (default light)
Solarized Dark, Solarized Light
Monokai Dimmed
Tomorrow Night Blue
One Dark Pro

The only 2 themes we don't (and can't) support, due to their lack of coloring, are:

Dark (Visual Studio), Light (Visual Studio)

If your custom theme doesn't seem to highlight much (e.g. no colors for upper-case JSX tag, no distinction between module and variant), try one of the recommended themes to see if that's the problem. For more info, see this post.

Installation

The plugin's on VSCode Marketplace. In VSCode, cmd-shift-p -> "Install Extensions", then find "rescript-vscode".

The plugin activates on .res and .resi files. If you've already got Reason-Language-Server installed, it's possible that the latter took precedence over this one. Make sure you're using this plugin ("ReScript syntax") rather than Reason-Language-Server ("BuckleScript syntax").

Features

Supports .res, .resi and bsconfig.json.
Syntax highlighting.
Formatting, with caveats:
- Currently requires the file to be part of a ReScript project, i.e. with a bsconfig.json.
- Cannot be a temporary file.
Build diagnostics.
Built-in bsb watcher (optional, and exposed explicitly as a pop-up; no worries of dangling build).
Type hint hover.
Jump to definition.
Autocomplete.
Find references.
Rename.
Snippets to ease a few syntaxes:
- external features such as @bs.module and @bs.val
- try, for, etc.
Folding, and custom folding through //#region and //#endregion.

Commands

`> ReScript: Create an interface file for this implementation file.`

Creates an interface file (.resi) for the current .res file, automatically filling in all types and values in the current file.

`> Open the compiled JS file for this implementation file.`

Opens the compiled JS file for the current ReScript file.

`> ReScript: Switch implementation/interface`

Switches between the implementation and interface file. If you're in a .res file, the command will open the corresponding .resi file (if it exists), and if you're in a .resi file the command will open the corresponding .res file.

This can also be triggered with the keybinding Alt+O.

Code Analyzer

The Code Analyzer is a mode in the extension that runs additional code analysis in your project. The analysis helps you find dead code at a granular level, find unhandled exceptions, and more.

The Code Analyzer uses reanalyze, which is embedded in the extension, so you don't need to install anything extra to run it.

Configuring the Code Analyzer

You'll need to configure what code analysis you want to run, and what (if any) directories you want to ignore. Configuration is done via adding reanalyze in bsconfig.json. You'll get autocomplete for what configuration options are valid. You can also read all about configuring reanalyze here.

Autostarting the Code Analyzer

The Code Analyzer needs to be started manually by default. However, you can configure the extension to start the Code Analyzer automatically via the setting rescript.settings.autoRunCodeAnalysis.

Usage

Open the command palette and run > ReScript: Start Code Analyzer. This will start code analysis in the ReScript project of the file you run the command from.

Dead code is highlighted in the editor, and code actions for suppressing dead code warnings are available in most cases.

When done, stop the code analysis mode by clicking the Stop Code Analyzer button in the editor status bar. This will clear all reported analysis warnings.

Caveats

Currently does not work for full monorepo dead code analysis (although it should work for each monorepo package individually).

Configuration

You'll find all ReScript specific settings under the scope rescript.settings. Open your VSCode settings and type rescript.settings to see them.

Autostarting ReScript builds

If there's no ReScript build running already in the opened project, the extension will prompt you and ask if you want to start a build automatically. You can turn off this automatic prompt via the setting rescript.settings.askToStartBuild.

Hide generated files

You can configure VSCode to collapse the JavaScript files ReScript generates under its source ReScript file. This will "hide" the generated files in the VSCode file explorer, but still leaving them accessible by expanding the source ReScript file they belong to.

Open your VSCode settings and type editor.filenesting. Enable the feature and scroll down to patterns.

The example has two patterns added:

This nests implementations under interfaces if they're present and nests all generated files under the main ReScript file. Adapt and tweak to your liking.

A screenshot of the result:

Use with Other Editors

This repo also contains a language server that can power other editors. However, the language server in this project is a pure implementation detail. We don't guarantee its stability for other editors' consumption apart from Vim and Sublime Text.

Still, if you'd like to use this language-server with other editors:

Get the release binaries from the Github Releases page.
Unzip the .vsix and get the server folder. That's the only folder you need.
The language server will be at server/out/server.js. Call it through node, and optionally pass --stdio if your editor doesn't support the default JSONRPC.

cknitt/rescript-vscode