How to use truffle-plugin-verify when you are not deploying the contract?

Question

Here is my A contract:

// SPDX-License-Identifier: MIT
pragma solidity >=0.4.22 <0.9.0;

contract A {
    B public b;

    constructor() public {
        b = new B();
    }
}

contract B {}

As you can see, it is deploying an instance of B in its constructor. For me, both A & B are important, so I want to verify them both on etherscan.

But while using truffle-plugin-verify, I am getting this error:

pam@g3:~/verify$ truffle run verify A B --network kovan --license MIT
Verifying A
Pass - Verified: https://kovan.etherscan.io/address/0xaf589F7A115b14C3825937bBd8A59203c84BE9c5#contracts
Verifying B
No instance of contract B found for network id 42
Failed to verify 1 contract(s): B

How can I verify the contract B here?

Answer 1

It is possible to specify the address of B separately. So in this case you have to manually figure out what address B was deployed to and run:

truffle run verify B@<address> --network kovan

If B was deployed from a contract and it has constructor arguments, you'd also need to manually retrieve those arguments (e.g. through Tenderly) and provide the ABI-encoded args with --forceConstructorArgs string:<constructorArgs>.