@nomiclabs/hardhat-ethers

hardhat-ethers

Hardhat plugin for integration with ethers.js.

What

This plugin brings to Hardhat the Ethereum library ethers.js, which allows you to interact with the Ethereum blockchain in a simple way.

Installation

npm install --save-dev @nomiclabs/hardhat-ethers 'ethers@^5.0.0'

And add the following statement to your hardhat.config.js:

require("@nomiclabs/hardhat-ethers");

Or, if you are using TypeScript, add this to your hardhat.config.ts:

import "@nomiclabs/hardhat-ethers";

Tasks

This plugin creates no additional tasks.

Environment extensions

This plugins adds an ethers object to the Hardhat Runtime Environment.

This object has the same API as ethers.js, with some extra Hardhat-specific functionality.

Provider object

A provider field is added to ethers, which is an ethers.providers.Provider automatically connected to the selected network.

Helpers

These helpers are added to the ethers object:

interface Libraries {
  [libraryName: string]: string;
}

interface FactoryOptions {
  signer?: ethers.Signer;
  libraries?: Libraries;
}

function getContractFactory(name: string, signer?: ethers.Signer): Promise<ethers.ContractFactory>;

function getContractFactory(name: string, factoryOptions: FactoryOptions): Promise<ethers.ContractFactory>;

function getContractFactory(abi: any[], bytecode: ethers.utils.BytesLike, signer?: ethers.Signer): Promise<ethers.ContractFactory>;

function getContractAt(name: string, address: string, signer?: ethers.Signer): Promise<ethers.Contract>;

function getContractAt(abi: any[], address: string, signer?: ethers.Signer): Promise<ethers.Contract>;

function getSigners() => Promise<ethers.Signer[]>;

function getSigner(address: string) => Promise<ethers.Signer>;

function getContractFactoryFromArtifact(artifact: Artifact, signer?: ethers.Signer): Promise<ethers.ContractFactory>;

function getContractFactoryFromArtifact(artifact: Artifact, factoryOptions: FactoryOptions): Promise<ethers.ContractFactory>;

function getContractAtFromArtifact(artifact: Artifact, address: string, signer?: ethers.Signer): Promise<ethers.Contract>;

The Contracts and ContractFactorys returned by these helpers are connected to the first signer returned by getSigners by default.

If there is no signer available, getContractAt returns read-only contracts.

Usage

There are no additional steps you need to take for this plugin to work.

Install it and access ethers through the Hardhat Runtime Environment anywhere you need it (tasks, scripts, tests, etc). For example, in your hardhat.config.js:

require("@nomiclabs/hardhat-ethers");

// task action function receives the Hardhat Runtime Environment as second argument
task(
  "blockNumber",
  "Prints the current block number",
  async (_, { ethers }) => {
    await ethers.provider.getBlockNumber().then((blockNumber) => {
      console.log("Current block number: " + blockNumber);
    });
  }
);

module.exports = {};

And then run npx hardhat blockNumber to try it.

Read the documentation on the Hardhat Runtime Environment to learn how to access the HRE in different ways to use ethers.js from anywhere the HRE is accessible.

Library linking

Some contracts need to be linked with libraries before they are deployed. You can pass the addresses of their libraries to the getContractFactory function with an object like this:

const contractFactory = await this.env.ethers.getContractFactory("Example", {
  libraries: {
    ExampleLib: "0x...",
  },
});

This allows you to create a contract factory for the Example contract and link its ExampleLib library references to the address "0x...".

To create a contract factory, all libraries must be linked. An error will be thrown informing you of any missing library.

Troubleshooting

Events are not being emitted

Ethers.js polls the network to check if some event was emitted (except when a WebSocketProvider is used; see below). This polling is done every 4 seconds. If you have a script or test that is not emitting an event, it's likely that the execution is finishing before the event is detected by the polling mechanism.

If you are connecting to a Hardhat node using a WebSocketProvider, events should be emitted immediately. But keep in mind that you'll have to create this provider manually, since Hardhat only supports configuring networks via http. That is, you can't add a localhost network with a URL like ws://localhost:8545.