ts-loader-fork-ts-checker

What This Rule Detects

This rule detects webpack configurations using ts-loader with transpileOnly: true or happyPackMode: true but missing fork-ts-checker-webpack-plugin.

Why It Matters

When ts-loader runs with transpileOnly: true or happyPackMode: true, TypeScript type checking is skipped during the bundling process for faster builds. Without fork-ts-checker-webpack-plugin, type errors will only surface at test time or not at all, delaying feedback in CI and potentially allowing type errors to reach production.

fork-ts-checker-webpack-plugin runs type checking in a separate process parallel to the build, giving you both fast builds and early type error detection.

Suggested Action

Add fork-ts-checker-webpack-plugin to your webpack plugins:

1. Install the plugin: npm install --save-dev fork-ts-checker-webpack-plugin
2. Add to your webpack config:

const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');

module.exports = {
  // ... your config
  module: {
    rules: [
      {
        test: /\.ts$/,
        loader: 'ts-loader',
        options: {
          transpileOnly: true // or happyPackMode: true
        }
      }
    ]
  },
  plugins: [
    new ForkTsCheckerWebpackPlugin()
  ]
};

When This Rule Is Skipped

This rule will NOT trigger if:

• No ts-loader: The webpack config does not use ts-loader
• No transpileOnly/happyPackMode: ts-loader is used without transpileOnly: true or happyPackMode: true (type checking is already happening)
• ForkTsCheckerWebpackPlugin present: The plugin is already configured

Measurement

Compare CI feedback time with and without fork-ts-checker-webpack-plugin. Type errors should be caught earlier without slowing down the build.

Compatibility Notes

• fork-ts-checker-webpack-plugin works with webpack 4 and 5
• Compatible with ts-loader versions that support transpileOnly and happyPackMode
• Can be configured to watch specific files or directories for type checking