Hardhat v2.19.0: Introducing Configuration Variables
Handling configuration settings is a common situation in Ethereum development, and it often involves sensitive information that could cause issues if leaked. A common example are Infura API keys. Different developers may also have varying settings, which adds to the complexity of managing these configurations.
Configuration variables are a new Hardhat feature that lets you use values in a configuration file without making them part of your codebase. They work as a replacement for environment variables and dotenv
, but are more secure, flexible, and powerful.
This is how most projects handle configuration values today:
module.exports = {
networks: {
sepolia: {
url: `https://sepolia.infura.io/v3/${process.env.INFURA_API_KEY}`,
},
},
};
These variables are then put in an .env
file and loaded using the dotenv
package. This approach works, but it has a couple of problems:
- A user might accidentally push the
.env
file to a public repository, making all the data within it accessible to other users or to bots. - It’s not clear which of these variables need to be set before running the project and which ones are optional.
- If you have multiple projects and want to share some value between them, you have to copy their
.env
files and keep them in sync.
Using configuration variables
Hardhat v2.19.0 introduces a new set of tasks under the vars
scope to manage your configuration variables:
$ npx hardhat vars set INFURA_API_KEY
✔ Enter value: ********************************
After setting a configuration variable, you can retrieve it from any Hardhat configuration using vars.get
:
const INFURA_API_KEY = vars.get("INFURA_API_KEY");
module.exports = {
networks: {
sepolia: {
url: `https://sepolia.infura.io/v3/${INFURA_API_KEY}`,
},
},
};
For variables that may not exist, you can specify a default value as the second parameter:
const salt = vars.get("DEPLOY_SALT", "12345");
You can also use vars.has
to check if a variable exists:
const accounts = vars.has("TEST_PK") ? [vars.get("TEST_PK")] : [];
Migrating from dotenv
If you are using dotenv
, we recommend migrating to our built-in configuration variables manager. This will make it easier to share values across various Hardhat projects, and will minimize the risk of exposing sensitive data by accidentally uploading a .env
file to a public repository.
To migrate from dotenv
, follow these steps:
- Replace
process.env.KEY
references in your configuration withvars.get("KEY")
. Replace conditions likeprocess.env.KEY !== undefined
withvars.has("KEY")
- Run
npx hardhat vars setup
to identify all the variables that are used by your project. - Use
npx hardhat vars set
for each variable as indicated by the setup task. - After substituting all instances of
process.env
, you may uninstall thedotenv
package and remove its import from your configuration.
Under the hood
Configuration variables are stored in plain text on your disk. Avoid using this feature for data you wouldn’t normally save in an unencrypted file. You can run npx hardhat vars path
to get the path to the storage file.
Give it a try
Upgrade to Hardhat v2.19.0 and check our Configuration variables guide to learn more. And don’t forget to star Hardhat on GitHub!