Using the Hardhat Chainlink Plugin

Overview

The Hardhat Chainlink Plugin offers a convenient way to integrate Chainlink functionality into your web3 development workflow by seamlessly interacting with Chainlink services within your Hardhat-based projects. Currently, the plugin supports Data Feeds, VRF, and Automation. It also provides a sandbox environment for running a local Chainlink node.

Objective

This tutorial shows you how to install and use the Hardhat Chainlink plugin.

Before you begin

• Install NodeJS
• Install a supported package manager: either npm or yarn
• If you don't have an existing Hardhat project, create one by following the Hardhat Getting Started guide, and then return to this guide.

Installation

You can install the Hardhat Chainlink plugin using either npm or yarn. Choose the package manager that you prefer and run one of the following commands:

npm install @chainlink/hardhat-chainlink

yarn add @chainlink/hardhat-chainlink

After installation, add the plugin to your Hardhat config:

require("@chainlink/hardhat-chainlink");

import "@chainlink/hardhat-chainlink";

This plugin also extends the Hardhat configuration and adds chainlink parameters group in your config file:

module.exports = {
  chainlink: {
    confirmations // Number of confirmations to wait for transactions, default: 1
  },
  ...
}

Choose how to use the plugin

The Hardhat Chainlink plugin offers multiple ways to interact with Chainlink services, giving you the flexibility to choose the approach that suits your workflow best:

Choose the method that fits your project's requirements and coding style. All three approaches provide the same set of functionalities, allowing you to interact with Chainlink services efficiently and effectively.

CLI

Interact with the Hardhat Chainlink plugin through the command-line interface (CLI) using the following format:

npx hardhat chainlink:{service} [method] [--args]

This approach serves both as a CLI method and Hardhat tasks. However, it's important to note that the methods in each service are "hidden" with subtasks and won't be shown when you call npx hardhat. Instead, you can call the methods by passing its name as a parameter for the related task.

If the subtask and/or args are not passed directly, they will be interactively inquired during the CLI command execution.

To get a list of all available methods (subtasks) and their arguments for a specific service, you can use:

npx hardhat chainlink:{task}:subtasks

Example of calling a subtask with arguments directly in the CLI:

npx hardhat chainlink:dataFeed getLatestRoundAnswer --args '{"dataFeedAddress": "0xE62B71cf983019BFf55bC83B48601ce8419650CC"}'

Example of interacting with the CLI interactively, where the subtask and arguments are inquired:

npx hardhat chainlink:dataFeed
# The CLI will ask you to select a subtask (getLatestRoundAnswer) and provide arguments interactively.

Hardhat tasks

Integrate the Hardhat Chainlink plugin as a subtask in your own Hardhat tasks. Use the following format to run a subtask:

hre.run("chainlink:{service}:{method}", { ...args });

This method is well-suited for more complex workflows and automation. You can call the {service} and {method} directly in your custom Hardhat tasks, passing the required arguments as an object containing the necessary parameters.

Example of calling a subtask in a custom Hardhat task with arguments:

task("myTask", "My custom task", async (taskArgs, hre) => {
  await hre.run("chainlink:dataFeed:getLatestRoundAnswer", {
    dataFeedAddress: "0xE62B71cf983019BFf55bC83B48601ce8419650CC",
  })
})

Methods in Hardhat environment

Directly access Chainlink services as methods in the Hardhat Environment using the following format:

hre.chainlink.{service}.{method}(...args);

This approach is ideal for seamless integration with your existing Hardhat project. You can use familiar JavaScript syntax to call the Chainlink services as methods within your scripts and tasks.

Example of calling a subtask as a method in the Hardhat Environment:

async function myFunction() {
  const dataFeedAddress = "0xE62B71cf983019BFf55bC83B48601ce8419650CC"
  const result = await hre.chainlink.dataFeed.getLatestRoundAnswer(dataFeedAddress)
  console.log(result)
}

Available services

The Hardhat Chainlink plugin supports the following Chainlink services:

• dataFeed (Data Feeds)
• dataFeedProxy (Data Feed Proxies)
• feedRegistry (Feed Registries)
• l2Sequencer (L2 Sequencers)
• ens (ENS - Ethereum Name Service)
• automationRegistry (Automation Registries)
• automationRegistrar (Automation Registrars)
• vrf (Verifiable Random Functions)

For a more in-depth understanding of available services and methods, please explore their tests.

Plugin registries

The Hardhat Chainlink plugin provides registries that contain information about smart contracts related to various Chainlink services and other data, such as the denominations library, which is useful for interacting with the Feed Registry.

In general, these registries help you access essential contract addresses deployed on different networks, making it easier to integrate Chainlink services into your projects.

Available registries

The Hardhat Chainlink plugin provides the following registries:

• dataFeeds: Addresses of Data Feeds-related contracts: Aggregators and Proxies, and their parameters.
• feedRegistries: Feed Registries' contract addresses.
• l2Sequencers: L2 Sequencer Uptime Feeds' contract addresses.
• keeperRegistries: Addresses of Automation-related contracts: Keeper Registry and Keeper Registrar.
• linkTokens: Link Tokens' contract addresses.
• vrfCoordinators: Addresses of VRF Coordinators and their parameters.
• denominations: Records from Denominations library to interact with Feed Registries contracts.

For a more in-depth understanding of the structure of these records, please explore their interfaces.

Using plugin registries

You can access the plugin registries using one of the following methods:

npx hardhat chainlink:registries [method]

npx hardhat chainlink:registries:subtasks

npx hardhat chainlink:registries getDataFeed
# The CLI will ask you to select a preferred network and subsequent parameters.

const registry = hre.chainlink.registries.{registryName};

async function myFunction() {
  const dataFeedAddress = hre.chainlink.registries.dataFeeds.ethereum.ETH.USD.contractAddress
  console.log(dataFeedAddress)
  // 0xE62B71cf983019BFf55bC83B48601ce8419650CC
}