oxlint-plugin-complexity

A linter plugin that analyzes code complexity metrics, helping developers identify and refactor hard-to-maintain code. Framework support spans React, Vue, Angular, Svelte, Astro, Solid, and Qwik, across .js, .mjs, .cjs, .ts, .tsx, .jsx, .vue, .svelte, and .astro files.

Installation

npm install oxlint-plugin-complexity --save-dev

Configuration

Add to your .oxlintrc.json. Cyclomatic and cognitive limits are configured together in a single complexity rule:

{
  "jsPlugins": ["oxlint-plugin-complexity"],
  "rules": {
    "complexity/complexity": [
      "error",
      {
        "cyclomatic": 20,
        "cognitive": 15
      }
    ]
  }
}

Actionable Error Messages

The plugin delivers detailed feedback with a summary, a line-by-line breakdown, and refactoring tips for the deepest nesting:

complexity(complexity): Function 'processData' has Cognitive Complexity of 15.
Maximum allowed is 10. [if: +14, for: +1]

Breakdown:
   Line 2: +1 for 'for'
>>> Line 6: +5 for 'if' (incl. +4 nesting) [top offender]
    ↳ Tip: Extract inner loops into helper functions — each extraction removes one nesting level

Metrics

Cyclomatic Complexity

Adds +1 for conditional branches, loops, case statements, catch, logical operators (&&, ||, ??), and ternaries.

Cognitive Complexity

Evaluates complexity considering nesting depth and specific patterns. React components using PascalCase naming that return JSX are excluded, as are standard default-value expressions. Only cognitive complexity tracks nesting depth, so refactoring tips require it.

Additional Features

• Standalone library — Analyze complexity programmatically via the /standalone and /diff entry points, no oxlint runtime needed
• Git diff analysis — Score only the functions touched by a diff for CI gates and pre-commit hooks
• Smart extraction suggestions — Variable-flow analysis identifies extractable blocks and proposes typed signatures
• Industry Standard — Based on established specifications for complexity measurement