Inconsistent loading of imported contracts into project

[gnpar]

Environment information

• brownie Version: v1.19.0
• ganache-cli Version: v7.3.2
• solc Version: 0.8.6
• Python Version: 3.8.10
• OS: linux

What was wrong?

There seems to be an issue with how contracts are loaded into the project.

When run on a clean directory (no build), imported contracts are loaded into the project's namespace.

When run a second time when the contracts were already built, only project contracts are loaded into the namespace.

It can be consistently reproduced:

1. Setup a new project

brownie init reproducer
cd reproducer

2. Create a simple contract in contracts/HelloWorld.sol:

pragma solidity ^0.8.0;

import {ERC1967Proxy} from "@openzeppelin/contracts/proxy/ERC1967/ERC1967Proxy.sol";

contract HelloWorld {
    string public message;

    constructor(string memory initMessage) {
        message = initMessage;
    }
}

3. Add remapping for external dependency in brownie-config.yaml:

compiler:
  solc:
    remappings:
    - "@openzeppelin=node_modules/@openzeppelin"

4. Install external dependency:

npm i @openzeppelin/contracts

5. Run the following script with brownie run scripts/reproducer.py:

import brownie


def main():
    try:
        getattr(brownie.project.ReproducerProject, "ERC1967Proxy")
        print("GOOD")
    except AttributeError:
        print(f"BAD {dir(brownie.project.ReproducerProject)}")

6. It should print "GOOD". Run it again: brownie run scripts/reproducer.py and it should print "BAD" followed by the listing of project attributes.

7. Remove the build directory and run again, it prints "GOOD"

How can it be fixed?

I've been looking at the code but am not sure how to fix it. The problem seems to have been introduced by #1411

Up until then, because all the contracts were always compiled all imported contracts were also loaded into the project.

If someone can point me in the right direction I may be able to provide a working patch.