How to Debug TypeScript with Node.js and VSCode Correctly?

Debugging TypeScript code in Node.js projects can sometimes lead to frustrating experiences, especially when working with multiple projects that have dependencies on each other. If you're encountering issues where VSCode's debugger steps into a temporary compiled JavaScript source instead of the original TypeScript files when debugging your project Foo, you've come to the right place. Let's address the common issues and provide you with clear solutions for setting up your debugging environment effectively. Understanding the Problem When you create a dependency between two Node.js projects, like Foo and Bar in this case, you might run into trouble with your breakpoints not being recognized. The debugger might often navigate through transpiled JavaScript files, making it challenging to debug your TypeScript source code. The main reason for this issue is related to source maps. Source maps are necessary for mapping the compiled JavaScript code back to the original TypeScript source files. If these maps are not properly configured, the debugger won’t load the TypeScript files correctly or won’t acknowledge the breakpoints set in them. Setting Up Your Environment 1. Configure tsconfig.json First, let's ensure that both projects have a correctly set up tsconfig.json file. You should have the following options in your tsconfig.json file for the Bar project: { "compilerOptions": { "outDir": "lib", "sourceMap": true, "module": "commonjs", "target": "es6", }, "include": ["src/**/*"], "exclude": ["node_modules"] } The crucial part here is the sourceMap property set to true, which ensures that source maps are generated during the compilation process. 2. Adjusting the Debugger Configuration Next, let’s modify the launch.json file in the Foo project to ensure that the debugger is aware of the source maps. Here’s an adjusted version of your launch.json file: { "version": "0.2.0", "configurations": [ { "name": "start", "request": "launch", "runtimeArgs": ["start"], "runtimeExecutable": "npm", "smartStep": true, "outFiles": ["${workspaceFolder}/../Bar/lib/**/*.js"], "sourceMaps": true, "type": "node" } ] } Notice the addition of the outFiles and sourceMaps properties. The outFiles property points to the compiled JavaScript files in the Bar project while allowing the debugger to map them back to the correct TypeScript source files. Setting sourceMaps to true further enhances the debugger's ability to link the original code with the compiled output. 3. Ensuring ts-node Options In your Foo project’s package.json, you already have a start script defined. To improve debugging, you can add option flags directly in the start script: "scripts": { "start": "ts-node --transpile-only --no-lazy --source-map src/index.ts" } By adding --source-map, you ensure that source maps are always generated during runtime, which can significantly improve debugging accuracy. Testing the Setup Once you have configured the above settings, please run your project using the debugger in VSCode. Place breakpoints in both Foo and Bar’s TypeScript files. When you start debugging, the VSCode debugger should hit the breakpoints set in Bar’s TypeScript source files allowing you to step through the TypeScript code rather than the compiled JavaScript. Frequently Asked Questions 1. Why are my breakpoints not being hit in the TypeScript files? This typically occurs due to missing or incorrect source maps. Ensure that both your projects are generating source maps by checking the sourceMap option in the tsconfig.json files. 2. Can I debug TypeScript files without installing ts-node? While you could use traditional JavaScript debugging methods, using ts-node makes the process smoother as it integrates TypeScript directly into Node.js without requiring pre-compilation steps. 3. What if I still cannot see the breakpoints? If you’re still facing issues, double-check the paths specified in outFiles of your launch.json file to ensure they accurately reflect your project structure. Sometimes, cleaning or rebuilding the project can also resolve lingering issues. Conclusion By correctly configuring both your tsconfig.json and launch.json files, as well as ensuring that your start command in package.json uses the necessary ts-node options, you can effectively debug your TypeScript projects in VSCode. This setup will streamline your development experience, allowing you to focus more on writing quality code without the headache of tracing compiled JavaScript sources.

May 7, 2025 - 20:35

How to Debug TypeScript with Node.js and VSCode Correctly?

Debugging TypeScript code in Node.js projects can sometimes lead to frustrating experiences, especially when working with multiple projects that have dependencies on each other. If you're encountering issues where VSCode's debugger steps into a temporary compiled JavaScript source instead of the original TypeScript files when debugging your project Foo, you've come to the right place. Let's address the common issues and provide you with clear solutions for setting up your debugging environment effectively.

Understanding the Problem

When you create a dependency between two Node.js projects, like Foo and Bar in this case, you might run into trouble with your breakpoints not being recognized. The debugger might often navigate through transpiled JavaScript files, making it challenging to debug your TypeScript source code.

The main reason for this issue is related to source maps. Source maps are necessary for mapping the compiled JavaScript code back to the original TypeScript source files. If these maps are not properly configured, the debugger won’t load the TypeScript files correctly or won’t acknowledge the breakpoints set in them.

Setting Up Your Environment

1. Configure tsconfig.json

First, let's ensure that both projects have a correctly set up tsconfig.json file. You should have the following options in your tsconfig.json file for the Bar project:

{
    "compilerOptions": {
        "outDir": "lib",
        "sourceMap": true,
        "module": "commonjs",
        "target": "es6",
    },
    "include": ["src/**/*"],
    "exclude": ["node_modules"]
}

The crucial part here is the sourceMap property set to true, which ensures that source maps are generated during the compilation process.

2. Adjusting the Debugger Configuration

Next, let’s modify the launch.json file in the Foo project to ensure that the debugger is aware of the source maps.

Here’s an adjusted version of your launch.json file:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "start",
            "request": "launch",
            "runtimeArgs": ["start"],
            "runtimeExecutable": "npm",
            "smartStep": true,
            "outFiles": ["${workspaceFolder}/../Bar/lib/**/*.js"],
            "sourceMaps": true,
            "type": "node"
        }
    ]
}

Notice the addition of the outFiles and sourceMaps properties. The outFiles property points to the compiled JavaScript files in the Bar project while allowing the debugger to map them back to the correct TypeScript source files. Setting sourceMaps to true further enhances the debugger's ability to link the original code with the compiled output.

3. Ensuring ts-node Options

In your Foo project’s package.json, you already have a start script defined. To improve debugging, you can add option flags directly in the start script:

"scripts": {
    "start": "ts-node --transpile-only --no-lazy --source-map src/index.ts"
}

By adding --source-map, you ensure that source maps are always generated during runtime, which can significantly improve debugging accuracy.

Testing the Setup

Once you have configured the above settings, please run your project using the debugger in VSCode. Place breakpoints in both Foo and Bar’s TypeScript files. When you start debugging, the VSCode debugger should hit the breakpoints set in Bar’s TypeScript source files allowing you to step through the TypeScript code rather than the compiled JavaScript.

Frequently Asked Questions

1. Why are my breakpoints not being hit in the TypeScript files?

This typically occurs due to missing or incorrect source maps. Ensure that both your projects are generating source maps by checking the sourceMap option in the tsconfig.json files.

2. Can I debug TypeScript files without installing ts-node?

While you could use traditional JavaScript debugging methods, using ts-node makes the process smoother as it integrates TypeScript directly into Node.js without requiring pre-compilation steps.

3. What if I still cannot see the breakpoints?

If you’re still facing issues, double-check the paths specified in outFiles of your launch.json file to ensure they accurately reflect your project structure. Sometimes, cleaning or rebuilding the project can also resolve lingering issues.

Conclusion

By correctly configuring both your tsconfig.json and launch.json files, as well as ensuring that your start command in package.json uses the necessary ts-node options, you can effectively debug your TypeScript projects in VSCode. This setup will streamline your development experience, allowing you to focus more on writing quality code without the headache of tracing compiled JavaScript sources.