Problem with using OpenZeppeling contracts with Hard Hat - not found: File import callback not supported

Question

I was writing and testing my smart contracts in Remix where I was importing some contracts from OpenZeppelin, and now I want to move it to my project in VSC. But now my VSC is screaming with an error:

Source "@openzeppelin/contracts/token/ERC20/ERC20.sol" not found: File import callback not supported

I went to documentation, I found that I have to install some of the packages to use OZ with Hard Hat like:

npm install --save-dev @openzeppelin/contracts
npm install --save-dev @openzeppelin/hardhat-upgrades
npm install --save-dev @nomiclabs/hardhat-ethers ethers # peer dependencies

https://docs.openzeppelin.com/upgrades-plugins/1.x/hardhat-upgrades

But it still not working it cannot find this contract even if I can see it installed in node_modules.

Here is my package.json dependencies:

{
  "devDependencies": {
    "@nomiclabs/hardhat-ethers": "^2.0.4",
    "@nomiclabs/hardhat-waffle": "^2.0.1",
    "@openzeppelin/contracts": "^4.4.2",
    "@openzeppelin/hardhat-upgrades": "^1.13.0",
    "chai": "^4.3.4",
    "ethereum-waffle": "^3.4.0",
    "ethers": "^5.5.3",
    "hardhat": "^2.8.0"
  }, 
  "dependencies": {}
}

Here is hardhat.config.js:

require('@nomiclabs/hardhat-waffle');
require("@nomiclabs/hardhat-ethers");
require('@openzeppelin/hardhat-upgrades');

module.exports = {
  solidity: '0.8.0',
  networks: {
    ropsten: {
      url: 'https://eth-ropsten.alchemyapi.io/v2/cds................Fa',
      accounts: ['private key']
    }
  }
}

I'm pretty new to Hard Hat, this is my first project.

This is an error I have:

---

EDIT

---

I fixed this issue by just change the import path to:

import "../node_modules/@openzeppelin/contracts/token/ERC20/ERC20.sol";

But then when I was running some tests with npx hardhat test I had compilation fail:

So I moved back to the normalimport "@openzeppelin/.../ERC20.sol"; and it compiled successfully, yet my VSC still screaming about that.

So HardHat can read those contract properly, there's just some problem with VSC that it cannot read those paths correctly. Someone know how to fix this?

Answer 1

I fixed this issue by just change the import path to:

import "../node_modules/@openzeppelin/contracts/token/ERC20/ERC20.sol";

But then when I was running some tests with npx hardhat test I had compilation fail:

So I moved back to the normalimport "@openzeppelin/.../ERC20.sol"; and it compiled successfully, yet my VSC still screaming about that.

So HardHat can read those contract properly, there's just some problem with VSC that it cannot read those paths correctly.

Answer 2

I used this command import '../node_modules/@openzeppelin/contracts/token/ERC20/ERC20.sol'; Now it's working.

Answer 3

Use single quotes instead of doubles.

Instead of:

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

use:

import '@openzeppelin/contracts/token/ERC20/ERC20.sol';

Answer 4

There is a little bit difference between importing the code in solidity and hardhat code

Solidity code

import "@openzeppelin/contracts/ownership/Ownable.sol";

hardhat code

import "@openzeppelin/contracts/access/Ownable.sol";

Change the path according to your requirement. You can see the contracts path in artificats/openzepeppelin/ contracts. So import accordingly.