@kolar-ai/eslint-config

Shared ESLint configuration for Kolar projects with TypeScript, NestJS, and Next.js support.

Installation

npm install --save-dev @kolar-ai/eslint-config

Peer Dependencies

Make sure you have the required peer dependencies installed:

npm install --save-dev \
  eslint@^8.0.0 \
  @typescript-eslint/eslint-plugin@^6.0.0 \
  @typescript-eslint/parser@^6.0.0 \
  eslint-plugin-import@^2.29.0

For frontend projects, also install:

npm install --save-dev \
  eslint-plugin-react@^7.33.0 \
  eslint-plugin-react-hooks@^4.6.0 \
  eslint-plugin-jsx-a11y@^6.8.0

Usage

Basic Setup

// eslint.config.js
const { configs } = require("@kolar-ai/eslint-config");

module.exports = [configs.base];

Backend (NestJS) Setup

// backend/eslint.config.js
const { configs } = require("@kolar-ai/eslint-config");

module.exports = [
  {
    ...configs.backend,
    files: ["**/*.ts"],
    ignores: ["dist/**", "node_modules/**"],
  },
];

Frontend (Next.js) Setup

// frontend/eslint.config.mjs
import kolarConfig from "@kolar-ai/eslint-config";
const { configs } = kolarConfig;

export default [
  {
    ...configs.frontend,
    files: ["**/*.ts", "**/*.tsx"],
    ignores: [".next/**", "out/**", "node_modules/**"],
  },
];

Custom Configuration

You can mix and match rules or use the helper function:

const { createConfig, baseRules } = require("@kolar-ai/eslint-config");

// Using the helper function
module.exports = [
  createConfig({
    type: "backend",
    withPrettier: true,
    withTesting: false,
    customRules: {
      "no-console": "off", // Override for development
    },
  }),
];

// Or manual configuration
module.exports = [
  {
    ...configs.backend,
    rules: {
      ...configs.backend.rules,
      // Your custom overrides
      "@typescript-eslint/no-explicit-any": "off",
    },
  },
];

Testing Files

For test files, you might want more relaxed rules:

const { configs, testingRules } = require("@kolar-ai/eslint-config");

module.exports = [
  {
    ...configs.backend,
    files: ["**/*.ts"],
    ignores: ["**/*.spec.ts", "**/*.test.ts"],
  },
  {
    ...configs.backend,
    files: ["**/*.spec.ts", "**/*.test.ts"],
    rules: {
      ...configs.backend.rules,
      ...testingRules,
    },
  },
];

With Prettier

If you're using Prettier, make sure to add eslint-config-prettier:

npm install --save-dev eslint-config-prettier

Then use it after our config:

const { configs } = require("@kolar-ai/eslint-config");
const prettier = require("eslint-config-prettier");

module.exports = [
  configs.backend,
  prettier, // Must come last to override formatting rules
];

Or use the built-in Prettier compatibility:

const { createConfig } = require("@kolar-ai/eslint-config");

module.exports = [
  createConfig({
    type: "backend",
    withPrettier: true, // This disables conflicting rules
  }),
];

What's Included

Base Rules

• TypeScript best practices
• Import ordering and organization
• Code quality and consistency
• Async/Promise handling
• Complexity limits

Backend Config (NestJS)

• All base rules
• Class naming conventions for NestJS
• Decorator positioning
• No default exports (NestJS pattern)
• Dependency injection patterns

Frontend Config (Next.js/React)

• All base rules
• React best practices
• React Hooks rules
• JSX accessibility (a11y)
• Next.js patterns (default exports for pages)

Testing Rules

• Relaxed rules for test files
• Allow any types in tests
• No console warnings
• No line limits

Configuration Options

createConfig Options

{
  type?: 'base' | 'backend' | 'frontend';
  withPrettier?: boolean;    // Disable formatting rules
  withTesting?: boolean;      // Apply relaxed testing rules
  customRules?: object;       // Your rule overrides
  customSettings?: object;    // Your settings overrides
}

Rule Categories

TypeScript Rules

• Naming conventions (interfaces with 'I' prefix, PascalCase for types)
• Type safety (no-explicit-any as warning)
• Async/await best practices
• Consistent type imports

Import Rules

• Alphabetical ordering within groups
• Grouped by type (builtin → external → internal → parent → sibling)
• Newlines between import groups
• No duplicate imports
• Cycle detection

Code Quality

• Complexity limits (max 15)
• Function size limits (max 100 lines)
• Max depth (4 levels)
• Prefer modern syntax (const, template literals, destructuring)
• Consistent equality checks

Framework Specific

NestJS:

• Class suffixes (Controller, Service, Repository, etc.)
• Decorator positioning
• No extraneous classes allowed

React/Next.js:

• Hooks rules enforcement
• JSX best practices
• Accessibility requirements
• Component naming (PascalCase)

Migrating from Old Config

If you're migrating from .eslintrc.json:

1. Install this package
2. Create eslint.config.js (or .mjs for frontend)
3. Remove old .eslintrc.json
4. Update scripts in package.json if needed

Troubleshooting

"Cannot find module" errors

Make sure all peer dependencies are installed.

Rules not applying

Check that your files glob patterns are correct and that the config is exported correctly.

Conflicts with Prettier

Either use eslint-config-prettier or enable withPrettier: true in createConfig.

Version History

• 1.0.0 - Initial release with base, backend, and frontend configs
• 1.0.1 - Added testing rules
• 1.0.2 - Added Prettier compatibility rules

License

MIT