Linting

Fusion apps use two linters together, each catching different things:

• Biome — general JavaScript/TypeScript formatting and correctness (unused variables, dead code, style)
• Fusion Lint — Fusion Framework-specific conventions (intent comments on control flow, TSDoc on exported APIs, no class components, and more)

Run both, in that order — Biome catches general issues, Fusion Lint catches Fusion-specific ones.

Install Fusion TS Lint in VS Code for inline squiggles as you type — no separate server to configure.

🔍 Fusion Lint

Fusion-specific lint rules for TypeScript — the stuff ESLint and Biome don't know about.

Squiggles in your editor. Failures in CI. Inline comments on pull requests.
All from one tool that understands how Fusion apps are supposed to be written.

Install in VS Code

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✨ What makes it different

Most linters check what your code does. Fusion Lint checks why.

Every if, for, and RxJS chain must be preceded by a comment explaining the intent. Every exported hook, component, and function must have TSDoc. The rules aren't pedantic — they're the conventions your team already agreed on, just enforced automatically.

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🚀 Jump in

I want to…	Go here
🖥️ Get squiggles in VS Code right now	vscode/ →
⌨️ Run lint in the terminal or pre-commit	cli/ →
⚙️ Wire it up in GitHub Actions	cli/ → CI →
📋 See every rule and what it catches	rules/ →
🎚️ Tune severities or turn rules off	config/ →
🔧 Write your own rule	core/ →

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👀 See it in action

Intent comments

// ❌ Fusion Lint: require-intent-comment/flow
if (user.role === 'admin') {
  redirect('/admin');
}

// ✅ Why is obvious — lint is happy
// Admins land on a dedicated dashboard with elevated controls
if (user.role === 'admin') {
  redirect('/admin');
}

TSDoc on public API

// ❌ Fusion Lint: require-hook-tsdoc
export const useContextData = (id: string): ContextData => { ... };

// ✅ One line is enough
/** Fetches and caches context data for the given context ID. */
export const useContextData = (id: string): ContextData => { ... };

Code style

// ❌ Fusion Lint: no-class-components
export class UserCard extends React.Component<Props> { ... }

// ✅
export const UserCard = ({ user }: Props): JSX.Element => ( ... );

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📦 Packages

core → rules → config → cli → lsp → vscode

Package	What it is
@equinor/fusion-framework-lint-core	Engine, Rule interface, Diagnostic type
@equinor/fusion-framework-lint-rules	All built-in rules
@equinor/fusion-framework-lint-config	recommended preset and config loader
@equinor/fusion-lint	CLI — fusion-lint check and fusion-lint changed
@equinor/fusion-framework-lint-lsp	LSP server for editor integration
fusion-ts-lint-vscode	VS Code extension — squiggles, Problems panel, hover messages

Biome

Biome formats and lints general JS/TS issues. A Fusion app's generated biome.json (via @equinor/fusion-framework-cli) is a good starting point — extend or copy it into your own project.

// biome.json
{
  "$schema": "https://biomejs.dev/schemas/2.2.5/schema.json",
  "formatter": {
    "enabled": true,
    "lineWidth": 100,
    "indentStyle": "space"
  },
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true
    }
  },
  "javascript": {
    "formatter": {
      "semicolons": "always",
      "quoteStyle": "single"
    }
  }
}

Install the Biome VS Code extension and set it as your default formatter:

// .vscode/settings.json
{
  "editor.defaultFormatter": "biomejs.biome",
  "editor.formatOnSave": true
}

Useful commands once Biome is added to your package.json scripts:

Command	What it does
biome check	Format + lint check (read-only)
biome format --write	Format files in place
biome lint	Lint only