Installation of openzeppelin/contracts Library

Question

I have created a node.js project, within which I have created a truffle directory and initialised its project. I have installed the openzeppelin (npm install @openzeppelin/contracts) library in this truffle project directory, but nothing appears to have been installed, although I did not received any error during the install process. The import statement in my project displays the error hereafter:

import "@openzeppelin/contracts/token/ERC721/ERC721Full.sol";

Source "@openzeppelin/contracts/token/ERC721/ERC721Full.sol" not found: File import callback not supported

Thank you. J

Answer 1

If you run npm uninstall @openzeppelin/contracts and then npm install @openzeppelin/[email protected], then retry the import, then it should work.

Also, check your truffle-config.js file and see if the root directory is configured properly to find your node_modules folder properly.

Answer 2

That's because ERC721Full.sol no longer exists, as you can see in the Github repository. From the latest update (v3.0) of the OpenZeppelin contracts, you can read the following:

ERC20 and ERC721 were simplified and streamlined, including all optional parts of the standard by default, and simplifying some of our own custom extensions.

[...]

If you're using the ERC20 or ERC721 tokens however, you'll have to remove all references to optional extensions (ERC20Detailed, ERC721Enumerable, etc.) - these have been included in the base contracts.

You should use ERC721.sol, which includes the parts of ERC721Full.sol:

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

If you want to install a specific version (example: v2.3.0):

npm install @openzeppelin/[email protected]