How to reference LINK token on (forked) development network without "invalid opcode"?

I like to run a number of local tests. Everything works well on rinkeby and other test chains. However, the local development chain disagrees with my configuration. When I run a forked development network:

brownie console --network mainnet-fork

The ganache-cli initiates as expected:

Brownie v1.18.1 - Python development framework for Ethereum

BlockchainProject is the active project.

Launching 'ganache-cli --accounts 10 --hardfork istanbul --fork https://mainnet.infura.io/v3/6a633a4ecae8449abbc69974cdd3a9b9 --gasLimit 12000000 --mnemonic brownie --port 8545 --chainId 1'...
Brownie environment is ready.

However, even the most simple contract interaction fails:

>>> link_token = Contract.from_explorer("0x514910771AF9Ca656af840dff83E8264EcF986CA")
Fetching source of 0x514910771AF9Ca656af840dff83E8264EcF986CA from api.etherscan.io...
>>> accounts[0].balance()
100000000000000000000
>>> accounts[1].balance()
100000000000000000000
>>> link_token.transfer(accounts[0].address, 100, {'from': accounts[0].address})
Transaction sent: 0x1542b679e4d09b2f4523427c7f5048ed01ee0d194c34cd27b82bbd177e1b3f23
  Gas price: 0.0 gwei   Gas limit: 12000000   Nonce: 2
  LinkToken.transfer confirmed (invalid opcode)   Block: 14604608   Gas used: 12000000 (100.00%)

<Transaction '0x1542b679e4d09b2f4523427c7f5048ed01ee0d194c34cd27b82bbd177e1b3f23'>

Since the Link token is compiled with an unsupported compiler I do not get any further information on why this results in LinkToken.transfer confirmed (invalid opcode).

How do I (correctly) run chainlink code against a forked development network using brownie - am I missing a step such as funding??

My networks: configuration in brownie-config.yaml:

networks:
  mainnet-fork:
    vrf_coordinator: '0xf0d54349aDdcf704F77AE15b96510dEA15cb7952'
    link_token: '0x514910771AF9Ca656af840dff83E8264EcF986CA'
    keyhash: '0xAA77729D3466CA35AE8D28B3BBAC7CC36A5031EFDC430821C02BC31A238AF445'

I did try to rm -rf build but that does not change anything.

System environment:

Brownie v1.18.1
Node 8.5.5
Ganache v7.0.4
21.3.0 Darwin Kernel Version (macOS 12.2.1)
Python 3.9.7

Solution

In this instance, the account used for Link token funding does not have any Link. For some reason, the transaction does not get reverted but the unlock: option of brownie provides assistance.

First adjusting the networks:settings to include an arbitrary account with a large Link balance:

  mainnet-fork:
    cmd_settings:
      unlock:
        - 0xf37c348b7d19b17b29cd5cfa64cfa48e2d6eb8db
    vrf_coordinator: '0xf0d54349aDdcf704F77AE15b96510dEA15cb7952'
    link_token: '0x514910771AF9Ca656af840dff83E8264EcF986CA'
    keyhash: '0xAA77729D3466CA35AE8D28B3BBAC7CC36A5031EFDC430821C02BC31A238AF445'

Second, run a mainnet-fork as before:

brownie console --network mainnet-fork

Third, confirm that the unlocked account is available and funded:

>>> accounts[10]
<Account '0xF37C348B7d19b17B29CD5CfA64cfA48E2d6eb8Db'>
>>> accounts[10].balance()
426496436000000000

Fourth, instantiate the contract of the token, Link in this instance:

link_token = Contract.from_explorer("0x514910771AF9Ca656af840dff83E8264EcF986CA")

Finally, transfer Link from the unlocked account to some other account (or contract):

link_token.transfer(accounts[0], 20, {"from": accounts[10]})

Alternatively, funding the mainnet address with Link, or even unlocking the Link owner and minting new Link would work too...