Understanding and Resolving ESLint Not Showing TypeScript Errors

Table of Contents

1. [Fundamental Concepts](#fundamental - concepts)
2. [Setting Up ESLint for TypeScript](#setting - up - eslint - for - typescript)
3. [Common Practices](#common - practices)
4. [Best Practices](#best - practices)
5. Conclusion
6. References

Fundamental Concepts

ESLint and TypeScript

ESLint is primarily designed for JavaScript. While it has support for TypeScript, it doesn’t have built - in type checking capabilities like the TypeScript compiler. TypeScript errors are related to type safety, such as incorrect type assignments, using non - existent properties on an object, etc. For ESLint to show TypeScript errors, it needs to be configured properly with TypeScript - specific plugins and parsers.

Parsers and Plugins

• Parser: A parser is responsible for converting the source code into an Abstract Syntax Tree (AST) that ESLint can analyze. For TypeScript, the @typescript-eslint/parser is used. It allows ESLint to understand TypeScript syntax.
• Plugins: Plugins are collections of rules and utilities that extend ESLint’s functionality. The @typescript-eslint/eslint-plugin provides a set of rules specifically for TypeScript.

Setting Up ESLint for TypeScript

Step 1: Install Dependencies

First, you need to install ESLint and the necessary TypeScript - related packages. In your project directory, run the following command:

npm install eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin --save-dev

Step 2: Initialize ESLint

Initialize ESLint in your project by running:

npx eslint --init

During the initialization process, you’ll be asked a series of questions. Make sure to select options that are appropriate for TypeScript, such as choosing the TypeScript support.

Step 3: Configure ESLint

Open the .eslintrc.js (or other configuration file format) and make the following changes:

module.exports = {
    parser: '@typescript-eslint/parser',
    parserOptions: {
        project: './tsconfig.json',
        tsconfigRootDir: __dirname,
        sourceType: 'module'
    },
    plugins: ['@typescript-eslint'],
    extends: [
        'eslint:recommended',
        'plugin:@typescript-eslint/recommended'
    ],
    rules: {
        // You can add custom rules here
    }
};

Step 4: Add Scripts to package.json

Add the following script to your package.json to easily run ESLint:

{
    "scripts": {
        "lint": "eslint src --ext .ts,.tsx"
    }
}

Now you can run npm run lint to check your TypeScript code for errors.

Common Practices

Using --fix Option

ESLint has a --fix option that can automatically fix many common errors. You can update the lint script in package.json to:

{
    "scripts": {
        "lint": "eslint src --ext .ts,.tsx --fix"
    }
}

Ignoring Files and Directories

Create an .eslintignore file in your project root to specify files and directories that ESLint should ignore. For example:

node_modules
dist

Best Practices

Keep Dependencies Up - to - Date

Regularly update ESLint, @typescript-eslint/parser, and @typescript-eslint/eslint-plugin to the latest versions. Newer versions often come with bug fixes and improved TypeScript support.

Write Custom Rules

If the built - in rules don’t meet your project’s specific requirements, you can write custom rules. You can use the @typescript-eslint framework to create rules that are aware of TypeScript types.

Integrate with IDE

Integrate ESLint with your IDE (e.g., Visual Studio Code). Most IDEs have ESLint extensions that can show errors in real - time as you code. In Visual Studio Code, you can install the ESLint extension and configure it to use your project’s ESLint configuration.

Conclusion

ESLint not showing TypeScript errors can be a challenging issue, but by understanding the fundamental concepts, setting up ESLint correctly, following common practices, and implementing best practices, you can ensure that ESLint effectively catches and reports TypeScript errors. This will help you maintain high - quality TypeScript code and improve your development workflow.

References

• ESLint Official Documentation
• @typescript-eslint Documentation

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