Invalid source name when trying to import openzeppelin inside a monorepo

[SebastienGllmt]

Goal

use @openzeppelin/contracts within a package in my monorepo

Error

I have a monorepo, and one of my packages is my evm contracts folder

root
    - node_modules
    - packages
        - evm-contracts
            - hardhat.config.ts
            - package.json
        - app

I want to use @openzeppelin/contracts from inside my package and use foundry so I've done the following:

1. I installed @openzeppelin/contracts and @openzeppelin/contracts-upgradeable
2. I installed @nomicfoundation/hardhat-foundry

Now, since dependencies for my project are hoisted to the root of the repository, I've set the following foundry configuration: @openzeppelin/=../../../node_modules/@openzeppelin/

This works and now foundry compiles. However, when I run npx hardhat compile I get the following error

HardhatError: HH1001: Invalid source name ../../../node_modules/@openzeppelin/contracts/token/ERC20/ERC20.sol. Expected source name but found a relative path.
    at validateSourceNameFormat (my-project/node_modules/hardhat/src/utils/source-names.ts:27:11)
    at Resolver.resolveSourceName (my-project/node_modules/hardhat/src/internal/solidity/resolver.ts:97:15)
    at Resolver.resolveImport (my-project/node_modules/hardhat/src/internal/solidity/resolver.ts:197:35)
    at async my-project/node_modules/hardhat/src/internal/solidity/dependencyGraph.ts:188:28
    at async Promise.all (index 0)
    at async DependencyGraph._addDependenciesFrom (my-project/node_modules/hardhat/src/internal/solidity/dependencyGraph.ts:186:5)
    at async Promise.all (index 0)
    at async Function.createFromResolvedFiles (my-project/node_modules/hardhat/src/internal/solidity/dependencyGraph.ts:15:5)
    at async Environment._runTaskDefinition (my-project/node_modules/hardhat/src/internal/core/runtime-environment.ts:358:14)
    at async Environment.run (my-project/node_modules/hardhat/src/internal/core/runtime-environment.ts:191:14)

Debugging

I tried to debug the resolveSourceName function in hardhat-core and found the following:

1. The input to the function is sourceName: "@openzeppelin/contracts/token/ERC20/ERC20.sol"
2. This gets updated to remappedSourceName: "../../../node_modules/@openzeppelin/contracts/token/ERC20/ERC20.sol"
3. It then crashes on the validateSourceNameFormat call in this function

Notably, this fails because validateSourceNameFormat explicitly disallows relative paths

Question

If relative paths are explicitly disabled, is there another way I can use @openzeppelin/contracts together with hardhat within my monorepo?

To be clear, removing import '@nomicfoundation/hardhat-foundry'; in my hardhat config solves the issue.

Possibly related: #4194 mentioned the remapping not being detected. In my case, it's definitely being detected (but the fact it's being used is breaking things)

[fvictorio]

Thank you @SebastienGllmt, I think this merits being an issue, so I opened #4734 to look into it next time we iterate the hardhat-foundry plugin.