Lesson 8: <unrecognized-selector> Issue

[0xTesty]

Hey,

I'm up to lesson 8: HTML / Javascript Fund Me (Full Stack / Front End), and running into an issue at around the 13 hour 17 minutes mark.

When I hit the fund button, MetaMask opens as expected with the correct amount of ETH ready for the transaction, but the transaction fails. Here is the error I'm getting in the hardhat console:

eth_call
  Contract call:       FundMe#<unrecognized-selector>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

  Error: VM Exception while processing transaction: reverted with reason string 'Didn't send enough'
      at FundMe.fund (contracts/FundMe.sol:64)
      at FundMe.<fallback> (contracts/FundMe.sol:52)

Here is my fund() function inside the FundMe.sol:

    function fund() public payable {
        require(
            msg.value.getConversionRate(s_priceFeed) >= MINIMUM_USD,
            "Didn't send enough"
        );

        // add funders to address array
        s_funders.push(msg.sender);

        // record who sent what amount
        s_addressToAmountFunded[msg.sender] = msg.value;
    }

Here is my fund() function from inside index.js on my front end:

async function fund() {
  const ethAmount = '0.1'

  console.log(`Funding with ${ethAmount} ETH...`)
  if (typeof window.ethereum !== 'undefined') {
    const provider = new ethers.providers.Web3Provider(window.ethereum)
    const signer = provider.getSigner()
    const contract = new ethers.Contract(contractAddress, abi, signer)

    const txResponse = await contract.fund({
      value: ethers.utils.parseEther(ethAmount),
    })
  } else {
    fundButton.innerHTML = 'Please install MetaMask'
  }
}

I thought initially that the amount was somehow wrong and so tried to set ethAmount to 1000 ETH, but it still reverted.

I have tried resetting the MetaMask account, still nothing...

I've tried looking in the usual places, but I cannot find the answer - please help!

[PatrickAlphaC]

So, the fact that you're seeing:

reverted with reason string 'Didn't send enough'

means that's the issue you're getting! What happens when you try sending 1 ETH instead of 1000?

[0xTesty]

Hey Patrick,

Great job on the course!

Unfortunately that doesn't work either, I'm still getting the same error:

eth_call
  Contract call:       FundMe#<unrecognized-selector>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

  Error: VM Exception while processing transaction: reverted with reason string 'Didn't send enough'
      at FundMe.fund (contracts/FundMe.sol:64)
      at FundMe.<fallback> (contracts/FundMe.sol:52)
      at HardhatNode.runCall (/home/0xtesty/hh-fcc/hardhat-fund-me/node_modules/hardhat/src/internal/hardhat-network/provider/node.ts:616:20)
      ...

Here's the updated fund() function:

async function fund() {
  const ethAmount = '1'

  console.log(`Funding with ${ethAmount} ETH...`)
  if (typeof window.ethereum !== 'undefined') {
    const provider = new ethers.providers.Web3Provider(window.ethereum)
    const signer = provider.getSigner()
    const contract = new ethers.Contract(contractAddress, abi, signer)

    const txResponse = await contract.fund({
      value: ethers.utils.parseEther(ethAmount),
    })
  } else {
    fundButton.innerHTML = 'Please install MetaMask'
  }
}

Interestingly when I set the MINIMUM_USD to zero inside the FundMe.sol contract. it appears to work, but I now see something else a little confusing in the contract call: <UnrecognizedContract>. Could this mean that there is an error inside my PriceConverter.sol?

Set minimum to zero:

uint256 public constant MINIMUM_USD = 0 * 1e18; // 1 * 10 ** 18

Response

eth_sendRawTransaction
  Contract call:       <UnrecognizedContract>
  Transaction:         0xecb05c75a3ceaaa22587a526f04db7c366b12216189767d4184fbd1c4a295ebc
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512
  Value:               1 ETH
  Gas used:            65145 of 65399
  Block #4:            0x61d2846f81fed9a9323bf4472fdd63968d81c91428b7ce2beea56bb59c38de83

eth_feeHistory (3)
eth_blockNumber
eth_getBlockByNumber
eth_getBalance
eth_getTransactionReceipt
eth_getBalance (2)
eth_getBlockByHash
eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

[neerajnerlekar]

Hi @0xTesty and @PatrickAlphaC,

I am facing the same issue also. When my: uint256 public constant MINIMUM_USD = 50 * 1e18;

eth_feeHistory
  Contract deployment: MockV3Aggregator
  Contract address:    0x5fbdb2315678afecb367f032d93f642f64180aa3
  Transaction:         0x2f60bd4cba5dffe33cd22380f4891cfadb7f13aad763bb084e8a1c3336b892f9
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  Value:               0 ETH
  Gas used:            569635 of 569635
  Block #1:            0x3ffc8c946d1e095f96d998c9c1ced344a9bb83b584ab819845ba5d32b3157322
  Contract deployment: FundMe
  Contract address:    0xe7f1725e7734ce288f8367e1bb143e90bb3f0512
  Transaction:         0x8c145c8496216abc4fb960822a8a95435f66c88027b14728faec84d7571fd0ee
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  Value:               0 ETH
  Gas used:            1013955 of 1013955
  Block #2:            0x8d255fbec19ab5893a8367e1e85e16663732d3c4dfd1ec90b4f542b60b67d85d

eth_blockNumber
eth_feeHistory
eth_blockNumber
net_version
eth_getBalance (2)
eth_getBlockByNumber
eth_getBalance
eth_blockNumber
eth_estimateGas
eth_getCode
eth_accounts
eth_call
  Contract call:       FundMe#<unrecognized-selector>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

  Error: VM Exception while processing transaction: reverted with reason string 'Didn't send enough'        
      at FundMe.fund (contracts/FundMe.sol:59)
      at FundMe.<fallback> (contracts/FundMe.sol:53)
      at HardhatNode.runCall (F:\eth\patrickC\hardhat-fund-me\node_modules\hardhat\src\internal\hardhat-network\provider\node.ts:616:20)
      at EthModule._callAction (F:\eth\patrickC\hardhat-fund-me\node_modules\hardhat\src\internal\hardhat-network\provider\modules\eth.ts:354:9)
      at HardhatNetworkProvider._sendWithLogging (F:\eth\patrickC\hardhat-fund-me\node_modules\hardhat\src\internal\hardhat-network\provider\provider.ts:139:22)
      at HardhatNetworkProvider.request (F:\eth\patrickC\hardhat-fund-me\node_modules\hardhat\src\internal\hardhat-network\provider\provider.ts:116:18)
      at JsonRpcHandler._handleRequest (F:\eth\patrickC\hardhat-fund-me\node_modules\hardhat\src\internal\hardhat-network\jsonrpc\handler.ts:188:20)
      at JsonRpcHandler._handleSingleRequest (F:\eth\patrickC\hardhat-fund-me\node_modules\hardhat\src\internal\hardhat-network\jsonrpc\handler.ts:167:17)
      at Server.JsonRpcHandler.handleHttp (F:\eth\patrickC\hardhat-fund-me\node_modules\hardhat\src\internal\hardhat-network\jsonrpc\handler.ts:52:21)

I think it's depositing the funds via the fallback function.

But, when I call the withdraw function, it shows the same VM Exception error and also withdraws the fund.

---

When I set uint256 public constant MINIMUM_USD = 0 * 1e18;

From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  Value:               0 ETH
  Gas used:            1010955 of 1010955
  Block #2:            0xcd3eb3dd9fc29b9cbd48159977d7c90651cafefcb392fc8cde810bf0d9ec07ce

eth_getBalance (2)
eth_getBlockByNumber
eth_blockNumber
eth_feeHistory
eth_blockNumber
net_version
eth_getBalance (2)
eth_getBlockByNumber
eth_getBalance
eth_blockNumber
eth_estimateGas
eth_getCode
eth_accounts
eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

eth_feeHistory
eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

eth_call
  Contract call:       <UnrecognizedContract>
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

eth_blockNumber
eth_feeHistory
eth_getTransactionCount
eth_blockNumber
eth_sendRawTransaction
  Contract call:       <UnrecognizedContract>
  Transaction:         0xb449e78316855c29e35592fec57b453d1fa7cdf9f02736d1cca30363fe4f5f6f
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512
  Value:               1 ETH
  Gas used:            104237 of 104237
  Block #3:            0xe2a2bd6fac906b44808a5fd228ec2e1750b09ccd811699ca17cf58dd9d36b33a

eth_feeHistory (2)
eth_getTransactionReceipt
eth_feeHistory

It deposits the funds through the fund function call.

And the withdraw function is also working.

eth_blockNumber
eth_feeHistory (2)
eth_blockNumber
eth_estimateGas
eth_getCode
eth_feeHistory
eth_blockNumber
eth_feeHistory
eth_getTransactionCount
eth_sendRawTransaction
  Contract call:       <UnrecognizedContract>
  Transaction:         0xe9dc42fa24029d5cc277e9d890f4a0c9bf063ad5960e0f2f6251399b4b178210
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512
  Value:               0 ETH
  Gas used:            35622 of 46753
  Block #4:            0xa21b6546d4a2017d5548099180b3b1616d5e26b21697bfc09b25eec1e54bd6ec

eth_feeHistory (2)
eth_getTransactionReceipt
eth_feeHistory
eth_blockNumber
eth_getBlockByNumber
eth_getTransactionReceipt
eth_getBalance (2)
eth_getBlockByHash

[neerajnerlekar]

@0xTesty

I noticed in your fund function it's

s_addressToAmountFunded[msg.sender] = msg.value;

while in the github code it's

s_addressToAmountFunded[msg.sender] += msg.value;

I had the same thing in my contract. I did change it, deleted the artifacts, cache and deployments/localhost, recompiled and ran yarn hardhat node.

Still getting the same error. Let me know if it works for you.

[0xTesty]

So in the end I cloned the finished project from both hardhat-fund-me-fcc and html-fund-me-fcc installed the dependencies, added the correct environment vars and tried it again. Unfortunately I get the same errors pretty much <UnrecognizedContract> and/or FundMe#<unrecognized-selector>.

BUT!! The contract and web app work as expected, I am able to deposit and withdraw.

It's unfortunate that I am getting these errors, but for now I am going to push on.

For anyone else looking at this discussion thread, I am starting to suspect that it may be something to do with my set-up (I am probably on some slightly older versions of things as I am a web developer already so have node etc installed since way before this course), here's my set-up:

OS: Windows 10 Pro
Terminal/environment: Windows Terminal / WSL2 (Ubuntu-20.04)
Node: v14.17.1
Yarn: 1.22.5
Git: 2.25.1

Hopefully that may offer some clues!

[neerajnerlekar]

Thanks for the update.

It was also working for me, so I have moved ahead.

[gonzales17]

I'm seeing the same issue. FYI, there's a stackoverflow post about this too, but no explanations or solutions yet, unfortunately:
https://stackoverflow.com/questions/72101643/hardhat-what-are-the-strange-calls-to-my-smart-contract

[PatrickAlphaC]

Looks like metamask is doing some weird stuff... If it's working for you, please just move ahead. If you'd like, please make an issue on the metamask github!

https://github.com/MetaMask/metamask-extension

[0xwurzel]

I'm getting the same issues. It seems to me that msg.value is being passed in as zero (I put some console.logging in FundMe.sol).

Does anyone know why that would be the case?

[0xwurzel]

Solved this to some extent. It appears that fund is actually being called by the fallback function. I'm not clear as to why (hence "to some extent").

However, if you put

if (msg.value > 0) {
...
}

around the call to fund() in the fallback function, the error goes away.

Incidentally I then got a nonce error but that was fixed by using Settings | Advanced | Reset account in metamask.
[edit - aha! Patrick mentions the reset a moment later in the video :-)]
[edit - missed out the zero after the >]

[imartin25]

After adding this

fallback() external payable {
        if (msg.value > 100) {
            fund();
        }
    }

to my fallback function I can now fund the contract from the web app. Ty

[JussaMouse]

However, if you put

if (msg.value > 0) {
...
}

around the call to fund() in the fallback function, the error goes away.

Thank you for sharing this! I was having the "send more ETH" error/ transaction revert too, and this fixed it. The hardhat node still says Contract call: <UnrecognizedContract> instead of Contract call: FundMe#fund, but I can live with that.

[hendythee]

Thanks, it works for me now!

[tonedblue]

Had the same error but managed to solve it. Wasnt actually anything to do with the code.
Their is a small gotcha when following the tutorial if you are not careful.
You connect your metamask to your account 1 which is on mainnet/rinkeby depending on what you used it for last.

After that you import an account using the private key from hardhat.
However, if you press the connect button and like me miss the pop up to connect account 2 you will end up connected on account 1 (that isnt hardhat) but not on account 2.

When you run fund it will call the contract and give
FundMe#<unrecognized-selector>
because you are connected to on account 1 (that isnt hardhat) but disconnected on the newly imported account 2 that is connected to hardhat.

Once I connected on account 2 the error went away.

Suprised that you can call the contract without being connected..

[PatrickAlphaC]

Ooooooooo that is interesting

[dgbweb3]

I'm 100% connected on my account 2 and on the Hardhat-Localhost but still getting the error.

FundMe#<unrecognized-selector>

[PatrickAlphaC]

It looks like this is due to some oddities with hardhat & metamask... If the tx goes though you can just ignore it for now.

[jcruzfff]

Kinda the same issue but I keep getting an eth_call error saying no fallback function I'm stuck with transaction reverted... can someone help?

  Contract call:       FundMe#<unrecognized-selector>
  From:                
  To:                  0xe7....

  Error: Transaction reverted: function selector was not recognized and there's no fallback function
      at FundMe.<unrecognized-selector> (contracts/FundMe.sol:16)

[alymurtazamemon]

@0xTesty this occurs due to the incorrect abi, a function could be missing in the abi or its parameters.

[egvandell]

I received this error too and can confirm the abi was double and triple checked

[alymurtazamemon]

@egvandell Check the below answer.

[geometrid]

Hi all, I'm enjoying Patrick's course along with you all! BTW great course, Patrick, thanks!! 👍

I've hit this issue as well, and I believe I've figured out what is going on. But I'm learning like many of you, so although I'm not 100% sure that this is the best solution, hopefully this reply makes sense and is helpful.

I started by console.log'ing some solidity special global vars from the fallback() function. The piece that pointed me to the above functions was msg.sig, which had various values when fallback() was called: 0x01ffc9a7, 0x313ce567, and 0x95d89b41. Googling "function signature 0x01ffc9a7" led me to the Ethereum Signature Database, for example this page for 0x01ffc9a7. supportsInterface sounded pretty legit, so I looked up the other two signatures as well. Then I found this stackoverflow question/answer on "Hardhat – What are the strange calls to my smart contract?", which provides some good hints to this issue. It seems that metamask is attempting to call some special contract methods: supportsInterface(bytes4 interfaceID), decimals(), and symbol() (and possibly name() as well, depending on if/how you implement supportsInterface). These are defined in various standards such as ERC165, ERC721, and ERC20.

I added dummy implementations for each the above methods to FundMe.sol to test this idea and it seems to work well for local development/testing purposes, but I don't know enough about smart contracts / solidity (yet!) to say whether it's a good solution. At the very least, the vague <unrecognized-selector> errors that show up in the hardhat node output resolve to the mentioned functions. Here is some sample hardhat node output from when I interact with the FundMe contract via the simple HTML web app and metamask after the methods are implemented:

eth_call
  Contract call:       FundMe#supportsInterface
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

  console.log:
    supportsInterface(_interfaceID) called! _interfaceID = 
    0x80ac58cd

eth_feeHistory
eth_call
  Contract call:       FundMe#supportsInterface
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

  console.log:
    supportsInterface(_interfaceID) called! _interfaceID = 
    0xd9b67a26

eth_call
  Contract call:       FundMe#decimals
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

  console.log:
    decimals() called! Returning 18

eth_call
  Contract call:       FundMe#symbol
  From:                0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266
  To:                  0xe7f1725e7734ce288f8367e1bb143e90bb3f0512

  console.log:
    symbol() called!

If there is enough interest, I could submit a PR to Patrick's html-fund-me-fcc repo. Hope this helps! 😄

[pigreekatgmaildotcom]

// * receive function
    receive() external payable {}

    // * fallback function
    fallback() external payable {}

It worked also for me! Thank you very much!!!

[Fikhas]

How do I add the implementation of those methods (supportsInterface(bytes4 interfaceID), decimals(), and symbol()) to FundMe.sol?

[AnneBBB]

@0xTesty Add receive and fallback functions also save us from errors (but still metamask will call these but now you do not need to worry about).

// * receive function
    receive() external payable {}

    // * fallback function
    fallback() external payable {}

Where do I add these?

[paulcoffee85]

after constructor()

[IgnacioGarcia198]

import "@openzeppelin/contracts/utils/introspection/IERC165.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
...
fallback() external payable {
        console.log("----- fallback:", msg.value);
    }

    receive() external payable {
        console.log("----- receive:", msg.value);
    }

    function supportsInterface(bytes4 interfaceID) external pure returns (bool) {
        return interfaceID == type(IERC20).interfaceId; // If your token is ERC-20
    }

    function decimals() public pure returns (uint8) {
        return 18;
    }

[anat1212]

Hi team, I made Minimum amount 0, it helped. But in metamask above the amount 0.5ETH i updated name to be "FUND", before there was questionmark which caused unrecongnized contract error. Here is screenshot after small update. May be it will help.

[techybolek]

What eventually helped me is the following three:

1. Realizing that upon invoking fund() always makes 4 incorrect calls with an unrecognized selector and there is no way around it. Those 4 incorrect calls must be captured by fallback().
2. As advised in the previous responses, the account must be reset whenever hardhat node is restarted
3. If it gets to the point where fund() results in ONLY in unrecognized selector calls, and the fund() method is NEVER invoked - manually disconnect the account from Metamask.

[aimaneharrak]

Hi,

MetaMask Account Reset was what worked for me !
But every time I launch the hardhat node, I have to reset the account again.

I feel like this has to do with the Nonce provided by MetaMask to the node,
as it complains about it being too high from the browser console.

To reset :

1. Settings from MetaMask Account tab
2. Advanced
3. Clear activity tab data

[darshilmistry]

Hey I think this error is happening due to some glitch in the hardhat node environment. When I got this error, I tried everything, I stripped the function to bare bones, I also tried the above method, but nothing worked for me. I would also like to mention at this point that the smart contract I was working with is a different one, that does not have any payable functions.

What fixed the problem for me was switching to a ganache for local testing. I reverted the contract to its original state and it worked flawlessly, without any errors.