Managing Environment Variables in a Vue.js Application with TypeScript

Many applications need to behave differently based on their environment (development, staging, production). Environment variables are a standard way to configure applications without hardcoding sensitive information or environment-specific settings directly into the codebase. This challenge focuses on implementing a robust and type-safe mechanism for accessing environment variables within a Vue.js application using TypeScript.

Problem Description

You need to create a Vue.js plugin that allows components and other parts of your application to access environment variables defined in a .env file. The plugin should:

1. Load Environment Variables: Load environment variables from a .env file (or .env.[environment] if specified). Assume the .env file is located in the root of your project.
2. Type Safety: Define a TypeScript type for the environment variables to ensure type safety when accessing them.
3. Centralized Access: Provide a global, accessible object (e.g., $env) within your Vue application to access the loaded environment variables.
4. Environment-Specific Overrides: Support loading environment variables from .env.[environment] files, where [environment] is the current environment (e.g., .env.development, .env.production). The environment should be configurable.
5. Default Values: Allow specifying default values for environment variables if they are not found in the .env file.

Expected Behavior:

• When the plugin is installed, it should parse the .env file and make the variables available globally.
• Accessing $env.API_URL (assuming API_URL is defined in the .env file) should return the corresponding value.
• If an environment variable is not defined, the default value (if provided) should be returned. Otherwise, undefined should be returned.
• The plugin should handle different environments correctly, loading the appropriate .env.[environment] file if available.

Edge Cases to Consider:

• Empty .env file.
• Invalid .env file format (e.g., missing = sign). While you don't need to perfectly validate the file, handle common errors gracefully.
• Environment variable names with special characters.
• Missing default values.
• Different environment configurations (e.g., development, production, staging).

Examples

Example 1:

.env:
API_URL=https://api.example.com
DEBUG=true

Input: Vue component accessing $env.API_URL and $env.DEBUG
Output: $env.API_URL returns "https://api.example.com", $env.DEBUG returns true
Explanation: The plugin loads the variables from the .env file and makes them accessible.

Example 2:

.env:
API_URL=https://api.example.com

Input: Vue component accessing $env.TIMEOUT
Output: $env.TIMEOUT returns undefined
Explanation: The TIMEOUT variable is not defined in the .env file, so undefined is returned.

Example 3:

.env.development:
API_URL=http://localhost:3000

Input: Vue application running in development mode accessing $env.API_URL
Output: $env.API_URL returns "http://localhost:3000"
Explanation: The plugin loads the .env.development file because the environment is development.

Constraints

• Environment Variable Format: Assume environment variables in the .env file are in the format KEY=VALUE.
• Environment Detection: The environment should be configurable via a plugin option (e.g., environment: 'development'). Default to 'development' if not provided.
• TypeScript: The solution must be written in TypeScript.
• Vue 3 Compatibility: The plugin should be compatible with Vue 3.
• Performance: The plugin should load the environment variables only once during application initialization. Avoid unnecessary re-parsing of the .env file.

Notes

• Consider using a library like dotenv to simplify the parsing of the .env file. However, you are not required to use it.
• Think about how to define the TypeScript type for the environment variables to ensure type safety.
• The plugin should be designed to be reusable and easy to integrate into different Vue.js projects.
• Focus on clarity, maintainability, and type safety in your solution. Good error handling is a plus.
• The global object $env should be available throughout the application after the plugin is installed.