Quick Start

This hands-on guide walks you through your first experience with the ReScript IntelliJ Plugin. Follow each step and verify the expected result before moving on.

Prerequisites

  • Plugin installed (Installation Guide)

  • A ReScript project with rescript.json (or bsconfig.json)

  • @rescript/language-server installed in the project (npm install -D @rescript/language-server)

Step 1: Open Your Project

  1. File → Open → Select your ReScript project folder (the directory containing rescript.json)

  2. Wait a few seconds for the IDE to index the project

Expected Result

  • The Project tree shows your src/ folder and rescript.json

  • A ReScript icon appears next to .res and .resi files in the project tree

  • The status bar at the bottom may show “ReScript” with a build status indicator

Troubleshooting

  • “Cannot find rescript.json”: Make sure you opened the project root directory, not a subdirectory

  • No ReScript icons on files: The plugin may not be installed correctly. Check Settings → Plugins → search for “ReScript”

  • Monorepo setup: If rescript.json is in a subdirectory, open that subdirectory as the project root, or ensure the language server is hoisted to the workspace root

Step 2: Verify Syntax Highlighting

Open any .res file from the project tree.

Expected Result

  • Keywords (let, type, module, switch) appear in a distinct color

  • Strings are colored differently from code

  • Comments (// and /* */) appear in a muted color

  • If the Language Server is running, you may see additional semantic coloring (e.g., module names, variant constructors)

Troubleshooting

  • All text is plain black/white: The file may not be recognized as ReScript. Check the file extension is .res or .resi

  • Partial highlighting only: This is normal during the first few seconds. Layer 1 (lexer) highlighting is instant; Layer 2 (semantic) highlighting appears once the Language Server starts

Step 3: Try Code Completion

Place your cursor inside a function body and start typing. For example, type Js.log or Console..

Press Ctrl+Space (Cmd+Space on macOS) to trigger completion manually.

Expected Result

  • A popup appears with context-aware suggestions (functions, modules, variables)

  • Each suggestion shows its type signature

  • You can also try postfix completion: type a value followed by .switch or .log and press Tab

Troubleshooting

  • No completions appear: The Language Server may not be running. Check the status bar for “ReScript” indicator

  • “Language server not found” notification: Install the language server with npm install -D @rescript/language-server, then restart the IDE

  • Only keywords appear: LSP-based completion requires a running Language Server. Native postfix/live templates work without it

Step 4: Navigate with Go to Definition

Hold Ctrl (Cmd on macOS) and click on any symbol — a function name, module name, or type. You can also press Ctrl+B (Cmd+B).

Expected Result

  • The editor jumps to the symbol’s definition, even if it’s in another file

  • You can also try Alt+F7 to find all usages of a symbol

  • Press Alt+O to switch between .res and .resi files

Troubleshooting

  • Nothing happens on Ctrl+Click: The Language Server needs to be running for Go to Definition. Check the status bar

  • “Cannot find declaration”: The symbol may be from an external library. Ensure dependencies are installed (npm install)

Step 5: See Diagnostics in Action

Intentionally introduce a type error — for example, change a string value to an int where a string is expected. Save the file or wait a moment.

Expected Result

  • Red wavy underlines appear on the erroneous code

  • Hovering over the underline shows the error message with type details

  • The Problems panel (Alt+6) lists all errors and warnings

  • If Error Lens is enabled, the error message appears inline at the end of the line

Troubleshooting

  • No underlines appear: The ReScript build watcher may not be running. Start it with Run → Edit Configurations → ReScript → Build Watch

  • Errors disappear immediately: This is expected after fixing the code. The Language Server updates diagnostics in real time

Step 6: Format Your Code

Press Ctrl+Alt+L (Cmd+Option+L on macOS) to format the current file.

Expected Result

  • The file is reformatted according to ReScript’s standard style using rescript format

  • Indentation, spacing, and line breaks are adjusted automatically

Troubleshooting

  • “Cannot find rescript binary”: The rescript CLI must be available in the project’s node_modules/.bin/. Run npm install to install dependencies

  • No visible changes: Your code may already be correctly formatted

Step 7: Run a Build

There are several ways to run a ReScript build:

  1. Gutter icon: Click the green ▶ icon in the gutter next to your file

  2. Run Configuration: Run → Edit Configurations → + → ReScript → Select “Build” or “Build Watch”

  3. Run Anything: Press Ctrl twice (double-tap Ctrl) and type rescript build

Expected Result

  • The Run tool window opens at the bottom showing the build output

  • The status bar shows the compilation result (success/error/warning count)

  • Build errors appear as clickable links in the console output

Troubleshooting

  • No ReScript option in Run Configurations: Make sure rescript.json exists in the project root

  • Build fails with “rescript not found”: Run npm install to install the ReScript compiler

Step 8: Explore Further

You’ve covered the core workflow. Here are more features to explore:

Structure View

Press Cmd+7 / Alt+7 to see an outline of your file’s modules, functions, and types.

Live Templates

Type let + Tab, sw + Tab, or comp + Tab to expand code snippets.

Intentions

Press Alt+Enter on any expression for quick actions: wrap with Some, add @genType, and more.

Find Usages

Press Alt+F7 on a symbol to see all places it’s used across the project.

What’s Next?