ReScript IntelliJ Plugin

ReScript language support for IntelliJ IDEA and other JetBrains IDEs.

Documentation · Version & Compatibility

Features

Language Support

• Syntax highlighting — Full JFlex lexer-based highlighting for .res and .resi files
• Semantic highlighting — Enhanced token coloring via LSP semantic tokens
• Code folding — Collapse blocks, comments, multi-line JSX, and custom //#region regions
• Brace matching — Automatic matching for {}, [], ()
• Smart quotes — Automatic quote pair completion
• Line & block comments — Toggle // and /* */ comments
• Spell checking — Integrated spell checker for comments and strings with bundled ReScript dictionary
• Breadcrumb navigation — Editor breadcrumbs showing current code context
• Navigation bar — Structure-aware navigation bar showing declaration hierarchy

Code Intelligence (via LSP)

• Code completion — Context-aware suggestions
• Go to definition — Navigate to symbol definitions
• Hover documentation — Inline type information and docs on hover
• Find references — Locate all usages of a symbol
• Find Usages — Symbol indexing and usage search for ReScript identifiers
• Rename refactoring — Safe project-wide renaming
• Diagnostics — Real-time error and warning display
• Inlay hints — Type annotations displayed inline
• Signature help — Parameter info for function calls
• Code Vision — Function type annotations via Code Lens
• Quick Documentation — PSI-based fallback documentation when LSP is unavailable (Ctrl+Q)
• Usage type classification — Categorized Find Usages results (open, type, pipe, JSX, etc.)
• Extract Variable — Extract selected expression into a let binding (Ctrl+Alt+V)
• Extract Function — Extract selected code into a new function (Ctrl+Alt+M)
• Inline Variable/Function — Inline expand variables and functions (Ctrl+Alt+N)
• Introduce Constant — Extract literal values into module-level constants
• Change Signature — Modify function parameters and update call sites (Ctrl+F6)
• React component extraction — Extract JSX into a new React component
• Safe Delete — Usage-checking safe delete refactoring (Refactor > Safe Delete)
• Name suggestions — Type-based and filename-based name suggestions during rename
• Completion Weigher — Context-based prioritization of completion candidates
• Pipe chain type hints — Inline intermediate type display for -> pipe chains
• Parameter Info — Native parameter info popup for labeled arguments (Ctrl+P)
• Unresolved reference Quick Fix — Add open or qualify unresolved references
• Generate function from usage — Create stub functions from call sites
• Type hole Quick Fix — Suggest candidate types for _ type holes
• Suggested refactoring — Automatic detection and proposal of code quality improvements

Navigation

• Go to Symbol — Stub-indexed quick symbol search (Cmd+Option+O)
• Structure view — Navigate module, function, and type declarations
• Switch .res/.resi — Toggle between implementation and interface files (Alt+O)
• Go to Related — Jump between .res, .resi, and compiled .js files
• Go to Implementation — Jump from .resi interface to .res implementation (Ctrl+Alt+B)
• Search Everywhere — Stub-indexed unified search for files, symbols, and actions (Shift+Shift)
• Go to Test — Navigate between implementation and test files, create test boilerplate (Ctrl+Shift+T)
• Open Compiled JavaScript — View compiled JS output (Alt+Shift+J)
• Create Interface File — Generate .resi from current .res file
• Module hierarchy — Visualize module dependency tree
• Call Hierarchy — View caller/callee relationships for functions (Ctrl+Alt+H)
• Copy qualified name — Copy fully-qualified module path (Cmd+Shift+Alt+C)
• Context Info — Sticky declaration header when scrolling through long files
• File include navigation — Navigate from open statements to their module files
• Goto Super — Jump from .res declaration to matching .resi declaration (Ctrl+U)
• External documentation — Open ReScript documentation for Belt/Js modules (Shift+F1)
• Type signature search — Search functions by type signature in Search Everywhere (Shift+Shift)
• Module dependency diagram — Visualize open/include relationships in a tool window with Mermaid + Graphviz DOT export

Editing Assistance

• Live Templates — 21 code snippets with ReScript-aware context (let, mod, sw, pipe, log, @module, @val, comp, etc.)
• Postfix Completion — 9 postfix templates: .switch, .pipe, .log, .some, .ok, .error, .ignore, .promise, .await
• Intention Actions — Wrap with Some/Ok/Error, add @genType, generate doc comment, add ->ignore, add _ prefix, remove redundant braces, fix identifier case, pipe ⇔ function call conversion, interface publish/unpublish, insert labeled args, merge switch cases, case split, convert to labeled args, remove unnecessary parentheses, remove redundant qualifier, expand destructuring, filter+map to filterMap, add type annotation, convert call to uncurried form, extract local module to file
• Surround With — Wrap selection in if/switch/try/block
• Unwrap/Remove — Remove wrapping constructs like Some(...), Ok(...), if, switch, try, { } (Ctrl+Shift+Delete)
• JSX auto-close — Automatically insert closing tags when typing > in JSX
• Generate actions — Generate switch arms, module types, make functions, record values, JSON encoder/decoder, and module type implementation (Cmd+N)
• Statement mover — Move declarations up/down (Alt+Shift+Up/Down)
• Smart Enter — Insert new line with correct indentation (Shift+Enter)
• Comment continuation — Auto-continue // and /** */ comments on Enter
• Smart join lines — Intelligent line joining for let bindings, pipe chains, and arrow functions
• Extend/shrink selection — Context-aware selection for strings, brackets, and comments
• File templates — Create Module, Interface, and React Component files
• Paste as JSON.t — Convert clipboard JSON to ReScript JSON.t
• .d.ts binding generation — Generate ReScript bindings from TypeScript definition files
• Backspace handler — Delete matching JSX tag pairs with backspace
• Move element — Swap comma-separated elements left/right (Alt+Shift+Cmd+Left/Right)
• Code block selection — Navigate to code block boundaries (Ctrl+Shift+[ / ])
• Split/Join list — Toggle between single-line and multi-line comma-separated lists
• Copy/Paste escaping — Auto-escape special characters when pasting into string literals
• Paste as JSX — Convert HTML clipboard content to ReScript JSX syntax (excludes React JSX)
• Paste as ReScript — Convert JavaScript/TypeScript clipboard content to ReScript syntax (type annotations stripped, JSX patterns converted)
• Strip trailing spaces — Protect whitespace inside string literals during trailing-space removal

Code Analysis & Inspections

• Error Lens — Inline diagnostic messages at end of editor lines (configurable severity) with structured type mismatch hints and diff highlighting
• Signature sync inspection — Detect .res/.resi signature mismatches
• Import optimizer — Auto-detect and remove unused/duplicate open statements
• Dead code analysis — Detect unused code via reanalyze integration with server mode acceleration (ReScript >= 12.1.0)
• Duplicate open detection — Warn on duplicate open statements
• Empty module detection — Warn on empty module declarations
• Missing rescript.json — Warn when configuration file is absent
• Highlight usages — Highlight related keywords (switch/if/try and matching control flow keywords)
• Problem filter — Suppress highlighting in node_modules/, lib/bs/, lib/ocaml/
• Inspection suppressor — Suppress inspections with // noinspection comments
• Format check — Highlight unformatted files with quick-fix to format (opt-in via Settings)
• Mutability diagnostics — Detect unnecessary ref bindings that are never reassigned
• Style linting — Detect redundant booleans, deprecated Belt.* usage, and boolean switch patterns

Build, Run & Test

• Run configuration — Build ReScript projects from the IDE with gutter run icons
• Run Anything — Execute ReScript CLI commands from Run Anything dialog (Ctrl+Ctrl)
• Expression type — Show inferred type at caret position (Ctrl+Shift+P)
• Completion confidence — Suppress auto-popup in comments and string literals
• Test runner — Run tests with auto-detected jest/vitest (SMTRunner test tree)
• Debugger integration — Debug compiled JavaScript via Node.js (Alt+Shift+D)
• Compiler status — Real-time build status in the status bar
• Console links — Clickable file:line links in compiler output
• Code formatting — Format via rescript format CLI (Cmd+Option+L)
• Scratch file — Run ReScript scratch files for quick experimentation
• REPL — Interactive ReScript execution environment in a tool window
• Worksheet mode — Interactively evaluate entire .resw files with inline results
• Build watch prompt — Suggestion balloon at project open to start rescript build -w

Project & IDE Integration

• LSP auto-install — One-click installation of @rescript/language-server with auto-detected package manager
• Project Wizard — Create new projects from 16 production-shaped templates (Basic, npm Library, CLI Tool, Vite+ + React, Next.js, Electron, two React Native flavors, Hono REST/GraphQL, Cloudflare Workers, AWS Lambda, Google Cloud Run, Monorepo, Full-Stack, res-x (HTMX on Bun)) with selectable package manager (npm / yarn / pnpm / bun) and validation library (zod / sury). Each template ships "one step deeper" sample code, a Vitest smoke test, MIT LICENSE, .nvmrc, GitHub Actions CI, and Dependabot config. See docs/templates.md for the full matrix.
• Compiled JS preview — Real-time preview of compiled JavaScript in a tool window
• Project View nesting — .resi interface files nested under corresponding .res files
• rescript.json support — Custom icon and JSON Schema for configuration files
• %raw() JS injection — JavaScript syntax highlighting inside %raw() blocks
• %re() RegExp injection — Regular expression highlighting and validation inside %re() blocks
• Type Info tool window — Always-visible panel showing inferred type at caret position
• Markdown code fence — ReScript syntax highlighting in Markdown code blocks
• Color settings — Customizable highlighting colors (Settings > Editor > Color Scheme > ReScript)
• Code style settings — Indentation configuration for ReScript files
• Code rearranger — Automatic declaration ordering (open → type → exception → module → external → let)
• Framework detector — Automatic ReScript project detection via rescript.json
• PPX annotation hints — Inline descriptions of PPX attribute effects
• PPX expansion view — View PPX macro expansion results in a tool window
• Comment code evaluation — Evaluate code examples in documentation comments
• TODO indexing — Track TODO/FIXME comments in ReScript files
• Editor notification — Guidance banner when LSP server is not detected
• File nesting — Compiled JS files (.res.js/.mjs/.cjs, .bs.js/.mjs/.cjs) nested under .res in Project view with subdued gray color
• Color preview — Inline color swatches in gutter for hex/rgb/hsl color values
• VCS Code Vision — Author and last-change annotations on declarations
• Project View decoration — "has interface" suffix and rescript.json version display
• Reader mode — Auto-enable reader mode for .res/.resi files in node_modules
• Package dependencies — Tool window showing rescript.json dependency tree
• Auto import options — Configurable auto-import settings in Settings > Editor > Auto Import
• Open statement index — Fast module lookup via file-based indexing of open statements
• Predefined code style — "ReScript Standard" preset code style
• Element descriptions — Enhanced element descriptions in refactoring dialogs
• Lookup char filter — Smart character filtering for completion item selection
• GitHub error reporter — Automatic error reporting to GitHub Issues for unhandled exceptions
• Editor floating toolbar — Quick access to Format, Open Compiled JS, and Create Interface actions
• Element signature provider — Persistent fold states across IDE restarts
• Index pattern builder — Enhanced TODO/FIXME pattern search in ReScript comments
• Grazie integration — Grammar and spell checking in comments and strings via Grazie plugin
• Injected language formatting — Code formatting support for injected language fragments
• Restart LSP action — Restart the ReScript Language Server from the Tools menu
• Dump LSP State — Export Language Server diagnostic state via Tools menu
• LSP initialization options — Send signatureHelp, cache, inlayHints, and compileStatus settings to the LSP server

Requirements

• IntelliJ IDEA 2025.3+ (or other JetBrains IDE with LSP support)
• Node.js installed and available in PATH
• @rescript/language-server installed:

# Local installation (recommended)
npm install @rescript/language-server

# Or global installation
npm install -g @rescript/language-server

Architecture

The plugin combines a JFlex lexer for fast, accurate syntax highlighting with the official ReScript Language Server for semantic features (completion, diagnostics, navigation, hover). A lightweight parser provides PSI structure for code folding and structure view.

For the full architecture overview — layers, Extension Points, and class-level mapping — see CLAUDE.md and docs/architecture.md.

Contributing

Developer-facing documentation lives in:

• CLAUDE.md — build commands, architecture layers, development conventions
• docs/ — permanent design documents (architecture, functional design, repository structure)
• sphinx-docs/dev/ — developer guide (setup, building, testing, contributing)
• .claude/rules/ — project rules (testing, Git conventions, documentation, release)

Quick reference:

./gradlew buildPlugin     # build the plugin
./gradlew runIde          # launch a sandbox IDE for manual testing
./gradlew test            # run unit tests
./gradlew ktlintCheck     # verify Kotlin formatting

License

MIT

Third-Party Licenses

This plugin depends on the following external components:

• @rescript/language-server — Licensed under LGPL-3.0-or-later. Not bundled; users install it separately via npm.
• rescript.json Schema — Derived from the rescript-compiler build-schema.json, licensed under LGPL-3.0-or-later.
• IntelliJ Platform SDK — Licensed under Apache License 2.0. Used at compile time only; not bundled.
• JFlex — Licensed under BSD-3-Clause. Used as a build tool only; generated code inherits this project's MIT license.