Solidity smart contract not working on local development network but working fine on goerli testnet

[usmanfarooq91]

I am new to learning solidity and python so please bear with me if you don't understand anything. you can find my project files here https://github.com/usmanfarooq91/nft-demo

I am trying to create a demo NFT contract using solidity and python on VS code with brownie. everything works fine on testnet goerli but its giving me the following error when I run it on local development network. even on development network contract deployes successfully and gets funding in LINK tokens to request the requestRandomness() function as it requires a 0.1 LINK as fee to perform the task but when it calls the requestRandomness() function it gives the below error.

I am using chainlink VRFcoordinator V1 so the nft can be assigned randomly.

on github please refer to the advance_collectible.sol and deploy_and_create.py script in advance_collectible folder.

PS C:\Users\usman\demos\nft-demo> brownie run scripts/advance_collectible/deploy_and_create.py
INFO: Could not find files for the given pattern(s).
Brownie v1.19.3 - Python development framework for Ethereum

NftDemoProject is the active project.

Launching 'ganache-cli.cmd --chain.vmErrorsOnRPCResponse true --wallet.totalAccounts 10 --hardfork istanbul --miner.blockGasLimit 12000000 --wallet.mnemonic brownie --server.port 8545'...

Running 'scripts\advance_collectible\deploy_and_create.py::main'...
The active network is development
Deploying Mocks
Transaction sent: 0x31eebe6b5f781486aa5356ac9de3425350e7f491818b5fac35d28d3b8a2035f6
  Gas price: 0.0 gwei   Gas limit: 12000000   Nonce: 0
  MockV3Aggregator.constructor confirmed   Block: 1   Gas used: 430659 (3.59%)
  MockV3Aggregator deployed at: 0x3194cBDC3dbcd3E11a07892e7bA5c3394048Cc87

Transaction sent: 0x96a442fa1d7b8289505da52450953e02ea7ab6be951db449cb81f871af3a4a1f
  Gas price: 0.0 gwei   Gas limit: 12000000   Nonce: 1
  LinkToken.constructor confirmed   Block: 2   Gas used: 669136 (5.58%)
  LinkToken deployed at: 0x602C71e4DAC47a042Ee7f46E0aee17F94A3bA0B6

Transaction sent: 0x95e2fd0de300a8d3e35d76303ce675c5902a4ef51d4e23699dab40f95e5d7769
  Gas price: 0.0 gwei   Gas limit: 12000000   Nonce: 2
  VRFCoordinatorMock.constructor confirmed   Block: 3   Gas used: 275069 (2.29%)
  VRFCoordinatorMock deployed at: 0xE7eD6747FaC5360f88a2EFC03E00d25789F69291

Mocks Deployed...
Transaction sent: 0xaf42aea4ac111661d68f1af710761d1351242e47160ef29c5cc1d4f969aaa04a
  Gas price: 0.0 gwei   Gas limit: 12000000   Nonce: 3
  AdvanceCollectible.constructor confirmed   Block: 4   Gas used: 2168334 (18.07%)
  AdvanceCollectible deployed at: 0x6951b5Bd815043E3F842c1b026b0Fa888Cc2DD85

Successfully deployed....
Transaction sent: 0x238ba75f818f034c7b4e4f99663a47a10a465fe46db85a980b663512921fce54
  Gas price: 0.0 gwei   Gas limit: 12000000   Nonce: 4
  LinkToken.transfer confirmed   Block: 5   Gas used: 51398 (0.43%)

  LinkToken.transfer confirmed   Block: 5   Gas used: 51398 (0.43%)

Contract funded!!
Transaction sent: 0x98783b208c9e00a3e0eb7955482fa8921fec270f0e4934b2560847c2bf57556f
  Gas price: 0.0 gwei   Gas limit: 12000000   Nonce: 5
  AdvanceCollectible.createCollectible confirmed (reverted)   Block: 6   Gas used: 60940 (0.51%)

  File "C:\Users\usman\.local\pipx\venvs\eth-brownie\lib\site-packages\brownie\_cli\run.py", line 51, in main
    return_value, frame = run(
  File "C:\Users\usman\.local\pipx\venvs\eth-brownie\lib\site-packages\brownie\project\scripts.py", line 110, in run
    return_value = f_locals[method_name](*args, **kwargs)
  File ".\scripts\advance_collectible\deploy_and_create.py", line 30, in main
    deploy_and_create()
  File ".\scripts\advance_collectible\deploy_and_create.py", line 23, in deploy_and_create
    tx = advance_collectible.createCollectible({"from": account})
  File "C:\Users\usman\.local\pipx\venvs\eth-brownie\lib\site-packages\brownie\network\contract.py", line 1864, in __call__        
    return self.transact(*args)
  File "C:\Users\usman\.local\pipx\venvs\eth-brownie\lib\site-packages\brownie\network\contract.py", line 1737, in transact        
    return tx["from"].transfer(
  File "C:\Users\usman\.local\pipx\venvs\eth-brownie\lib\site-packages\brownie\network\account.py", line 682, in transfer
    receipt._raise_if_reverted(exc)
  File "C:\Users\usman\.local\pipx\venvs\eth-brownie\lib\site-packages\brownie\network\transaction.py", line 446, in _raise_if_reverted
    raise exc._with_attr(
VirtualMachineError: revert
Trace step -1, program counter 4470:
  File "C:/Users/usman/.brownie/packages/smartcontractkit/chainlink-brownie-contracts@1.1.1/contracts/src/v0.6/VRFConsumerBase.sol", line 161, in VRFConsumerBase.requestRandomness:
    function requestRandomness(bytes32 _keyHash, uint256 _fee)
      internal returns (bytes32 requestId)
    {
      LINK.transferAndCall(vrfCoordinator, _fee, abi.encode(_keyHash, USER_SEED_PLACEHOLDER));
      // This is the seed passed to VRFCoordinator. The oracle will mix this with
      // the hash of the block containing this request to obtain the seed/input
      // which is finally passed to the VRF cryptographic machinery.
Terminating local RPC client...

To my understanding I think there is a problem with development network settings but I can not figure it out. I have tried changing the keyhash and fee, I have also tried to fund the contract with more link tokens but it doesn't seem to work.

[Nlferu]

Hello @usmanfarooq91

You have incorrect VRFCoordinatorMock.sol contract implemented under your contracts/test folder.

Correct this function in it as below:

function onTokenTransfer(
        address sender,
        uint256 fee,
        bytes memory _data
    ) public onlyLINK {
        (bytes32 keyHash, uint256 seed) = abi.decode(_data, (bytes32, uint256));
        emit RandomnessRequest(sender, keyHash, seed);
    }

You are just missing uint256 fee there currently and rest of your code is correct and this will work. Not sure how could you get this contract incorrectly tho as you should copy it from repo and don't touch it :p

[usmanfarooq91]

Hello @Neftyr,

Thank you so much, you saved my day. now that you have mentioned I remember now that it was me who removed uint256 fee from the VRFCoordinator.sol as I was experimenting with different versions of solidity. At version 0.8.0 it gave me a warning that uint256 fee isn't been used anywhere in the contract so I removed it and forgot to write it back when finally settling for the the right version. So my bad!

Thanks again for helping.

[Nlferu]

I'm glad I could help, thanks for explanation what happened to that VRF contract :D best of luck for you friend! ;)