Using Custom Environment Variables in Launch JSON: A Step-by-Step Guide for VSCode

Environment variables are crucial in software development and debugging, as they allow you to configure your application dynamically without hardcoding values. In Visual Studio Code (VSCode), you can use custom environment variables in the launch.json file to tailor your debugging environment. This flexibility helps manage different configurations for development, testing, and production, ensuring your application behaves correctly across various environments.

Setting Up launch.json

To create and configure a launch.json file in Visual Studio Code:

1. Open the Run and Debug view: Click on the Run and Debug icon in the Activity Bar or use the shortcut Ctrl+Shift+D.
2. Create a launch.json file: If you don’t have one, click on “create a launch.json file” in the Run start view.
3. Select Environment: Choose the environment (e.g., Node.js, Python) you want to configure.

In the launch.json file, you can set up custom environment variables using the env property. Here’s an example configuration:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Launch Program",
      "type": "node",
      "request": "launch",
      "program": "${workspaceFolder}/app.js",
      "env": {
        "NODE_ENV": "development",
        "API_KEY": "your_api_key_here"
      }
    }
  ]
}

In this example:

• "env": This property is used to define custom environment variables. Each variable is specified as a key-value pair, allowing you to set up the necessary environment for your application.

This setup ensures your application runs with the specified environment variables, making it easier to manage different configurations for development, testing, and production environments.

Defining Custom Environment Variables

To define custom environment variables in launch.json for Visual Studio Code, follow these steps:

1. Open launch.json:

   • Navigate to the .vscode folder in your project directory.
   • Open the launch.json file.

2. Add the environment property:

   • Inside the configuration object, add the environment property. This property accepts an array of objects, where each object has a name and value field.

3. Define environment variables:

   • Specify your environment variables within the environment array.

Example Syntax and Structure

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Launch Program",
      "type": "node",
      "request": "launch",
      "program": "${workspaceFolder}/app.js",
      "environment": [
        {
          "name": "NODE_ENV",
          "value": "development"
        },
        {
          "name": "API_KEY",
          "value": "your_api_key_here"
        }
      ]
    }
  ]
}

In this example:

• The environment array contains two environment variables: NODE_ENV and API_KEY.
• Each variable is defined with a name and value.

This setup ensures that when you launch your program, these environment variables will be available in the runtime environment.

Using Custom Environment Variables

To use custom environment variables in launch.json during debugging sessions in Visual Studio Code, follow these steps:

1. Open launch.json:

   • Go to the Debug view (Ctrl+Shift+D).
   • Click on the gear icon to open launch.json.

2. Define Environment Variables:

   • Add the env property within your configuration.
   • Specify your variables as key-value pairs.

Here’s a practical example:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Launch Program",
      "type": "node",
      "request": "launch",
      "program": "${workspaceFolder}/app.js",
      "env": {
        "NODE_ENV": "development",
        "API_KEY": "your_api_key_here"
      }
    }
  ]
}

In this example:

• NODE_ENV is set to development.
• API_KEY is set to your_api_key_here.

3. Access Environment Variables in Your Code:
   • In your application, you can access these variables using process.env.

Example in Node.js:

console.log(process.env.NODE_ENV); // Output: development
console.log(process.env.API_KEY);  // Output: your_api_key_here

This setup ensures that when you start a debugging session, the specified environment variables are available to your application.

Common Issues and Troubleshooting

Common Issues:

1. Incorrect Property Name: Using env instead of environment.
2. Syntax Errors: Missing commas, braces, or incorrect JSON format.
3. Path Issues: Incorrect paths for environment files or variables.
4. Debugger Compatibility: Some debuggers may not support certain environment variable formats.
5. Variable Substitution: Issues with ${} variable substitution in envFile.

Troubleshooting Tips:

1. Use Correct Property: Ensure you use environment instead of env.
2. Validate JSON: Use a JSON validator to check for syntax errors.
3. Check Paths: Verify paths in envFile and ensure they are correct.
4. Debugger Documentation: Refer to the debugger’s documentation for supported formats.
5. Variable Substitution: Ensure variables in envFile are correctly formatted and supported.

To use custom environment variables in `launch.json` in VSCode

follow these steps:

1. Open your project’s `launch.json` file by clicking on the Run icon in the Activity Bar and selecting “Edit Configurations” from the dropdown menu.
2. In the `launch.json` file, add a new configuration or edit an existing one to include environment variables.
3. Use the `env` property within your configuration to specify custom environment variables as key-value pairs.

Practical Example

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Launch Program",
      "type": "node",
      "request": "launch",
      "program": "${workspaceFolder}/app.js",
      "env": {
        "NODE_ENV": "development",
        "API_KEY": "your_api_key_here"
      }
    }
  ]
}

Accessing Environment Variables in Code

To access these environment variables in your code, use `process.env`. For instance:

console.log(process.env.NODE_ENV); // Output: development
console.log(process.env.API_KEY);  // Output: your_api_key_here

Troubleshooting Tips

This setup ensures that when you start a debugging session, the specified environment variables are available to your application.

Common issues include incorrect property names, syntax errors, path issues, debugger compatibility, and variable substitution. Troubleshooting tips include using the correct property name, validating JSON, checking paths, referring to the debugger’s documentation, and ensuring variable substitution is correctly formatted and supported.