Config Environment Variables Override

TODO: collapasable, copyable, download, etc

I'm trying to use .env in teh following way

1. read env variables from .env
2. read env variables from /etc/deductive/...
3. Anything in /etc should override the .env file settings

here is my code

const PROD_CONFIG_OVERRIDE_PATH = "/etc/deductive/app-ui-config";

if (!configFileLock) {
  configFileLock = true;

  if (fs.existsSync(PROD_CONFIG_OVERRIDE_PATH)) {
    console.log('AOK ', PROD_CONFIG_OVERRIDE_PATH, 'exists, reading');
    console.log(process.env);
    const result = dotenv.config({ path: PROD_CONFIG_OVERRIDE_PATH });
    console.log(result);
    

and when I read the values in code later it is with process.env.FOOTo achieve the desired behavior of reading environment variables first from a .env file and then overriding them with variables from /etc/deductive/..., you need to ensure that you load both sets of environment variables correctly and in the right order. Here's an approach to implement this:

1. Load variables from the .env file.
2. Load variables from /etc/deductive/..., which will override any matching variables from the .env file.

Here’s how you can do it:

const fs = require('fs');
const dotenv = require('dotenv');

const ENV_PATH = '.env';
const PROD_CONFIG_OVERRIDE_PATH = '/etc/deductive/app-ui-config';

// Load environment variables from .env file
dotenv.config({ path: ENV_PATH });

// Check if the production config override path exists and load its variables
if (fs.existsSync(PROD_CONFIG_OVERRIDE_PATH)) {
  const result = dotenv.config({ path: PROD_CONFIG_OVERRIDE_PATH });

  if (result.error) {
    throw result.error;
  }
  
  console.log('AOK', PROD_CONFIG_OVERRIDE_PATH, 'exists, reading');
  console.log(result.parsed);
}

// Now process.env contains the merged environment variables
console.log(process.env);

// You can now access your environment variables
const foo = process.env.FOO;
console.log(`FOO: ${foo}`);

Explanation

1. Load the .env file: The first dotenv.config({ path: ENV_PATH }) loads environment variables from your .env file and populates process.env with these variables.
2. Load the override file: If the file at PROD_CONFIG_OVERRIDE_PATH exists, it will be loaded next. Any variables defined in this file will override the corresponding variables already set by the .env file.

Key Points

• The fs.existsSync(PROD_CONFIG_OVERRIDE_PATH) check ensures that the override file exists before attempting to load it.
• dotenv.config({ path: PROD_CONFIG_OVERRIDE_PATH }) loads the environment variables from the specified path.
• If any environment variables are present in both the .env file and the override file, the values from the override file will replace those from the .env file.

This approach ensures that environment variables from /etc/deductive/... override those from the .env file, fulfilling your requirements.dotenv itself automatically loads .env files... so this code you provide doesn't add any gaurentee of ordering, right? You're correct that dotenv automatically loads variables from a .env file by default. To ensure proper ordering and guarantee that environment variables from /etc/deductive/... override those from the .env file, you need to explicitly load the .env file first and then load the override file.

Here’s a refined approach:

1. Explicitly load the .env file.
2. Explicitly load the override file if it exists.

const fs = require('fs');
const dotenv = require('dotenv');

const ENV_PATH = '.env';
const PROD_CONFIG_OVERRIDE_PATH = '/etc/deductive/app-ui-config';

// Load environment variables from .env file explicitly
dotenv.config({ path: ENV_PATH });

// Check if the production config override path exists and load its variables
if (fs.existsSync(PROD_CONFIG_OVERRIDE_PATH)) {
  const result = dotenv.config({ path: PROD_CONFIG_OVERRIDE_PATH });

  if (result.error) {
    throw result.error;
  }
  
  console.log('AOK', PROD_CONFIG_OVERRIDE_PATH, 'exists, reading');
  console.log(result.parsed);
}

// Now process.env contains the merged environment variables
console.log(process.env);

// You can now access your environment variables
const foo = process.env.FOO;
console.log(`FOO: ${foo}`);

Explanation

1. Explicitly Load the .env File: dotenv.config({ path: ENV_PATH }) ensures that environment variables from the .env file are loaded first.
2. Explicitly Load the Override File: If the file at PROD_CONFIG_OVERRIDE_PATH exists, it is loaded next with dotenv.config({ path: PROD_CONFIG_OVERRIDE_PATH }). This ensures that any environment variables defined in the override file will overwrite those from the .env file.

Important Note

Since dotenv does automatically load the .env file if present, it is crucial to call dotenv.config({ path: ENV_PATH }) before checking for and loading the override file. This ensures that the ordering is maintained and the override file has the final say.

This approach guarantees the correct ordering and ensures that environment variables from /etc/deductive/... override those from the .env file.But what if dotenv library later loads .env behind my back?To ensure that you control the loading order of environment variables and prevent dotenv from loading the .env file automatically behind your back, you can use dotenv's override option introduced in [email protected]. This option allows you to explicitly control the loading sequence and ensure that the environment variables from the override file take precedence.

Here is the updated code to ensure that the environment variables from /etc/deductive/... override those from the .env file:

const fs = require('fs');
const dotenv = require('dotenv');

const ENV_PATH = '.env';
const PROD_CONFIG_OVERRIDE_PATH = '/etc/deductive/app-ui-config';

// Explicitly load environment variables from .env file
dotenv.config({ path: ENV_PATH, override: false });

// Check if the production config override path exists and load its variables
if (fs.existsSync(PROD_CONFIG_OVERRIDE_PATH)) {
  const result = dotenv.config({ path: PROD_CONFIG_OVERRIDE_PATH, override: true });

  if (result.error) {
    throw result.error;
  }
  
  console.log('AOK', PROD_CONFIG_OVERRIDE_PATH, 'exists, reading');
  console.log(result.parsed);
}

// Now process.env contains the merged environment variables
console.log(process.env);

// You can now access your environment variables
const foo = process.env.FOO;
console.log(`FOO: ${foo}`);

Explanation

1. Explicitly Load the .env File: dotenv.config({ path: ENV_PATH, override: false }) ensures that environment variables from the .env file are loaded first. The override: false option specifies that these variables should not override any existing environment variables.
2. Explicitly Load the Override File: If the file at PROD_CONFIG_OVERRIDE_PATH exists, it is loaded next with dotenv.config({ path: PROD_CONFIG_OVERRIDE_PATH, override: true }). The override: true option ensures that any environment variables defined in the override file will overwrite those from the .env file.

Important Note

The override option is crucial here to prevent dotenv from automatically loading the .env file again and potentially causing conflicts. By setting override appropriately, you can control the priority of environment variables explicitly.

This approach guarantees that the environment variables from /etc/deductive/... will override those from the .env file, maintaining the desired order and ensuring consistency.

Config Environment Variables Override created at Tue Jan 20 1970 20:38:09 GMT+0000 (Coordinated Universal Time)