web3 - Error when calling sendTransaction with @truffle/contract on Ropsten Infura

Question

My smart contract is already deployed on Ropsten TestNet provided by Infura at 0x63865E0F065C7b865e1a2EE4d99C383A414Bec22 address. I want to sendTransaction using NodeJS(v.10.16.1) + Web3(v.1.2.6) + @truffle/contract(v.4.1.11). This is my NodeJS code -

var express = require('express');
var app = express();
var bodyParser = require('body-parser');
var session = require('express-session');

var Web3            = require('web3');
var contract        = require("@truffle/contract");
var path            = require('path');
var MyContractJSON  = require(path.join(__dirname, 'build/contracts/contract.json'));

var provider    = new Web3.providers.HttpProvider("https://ropsten.infura.io/v3/PROJECT_ID");

var MyContract = contract(MyContractJSON);
MyContract.setProvider(provider);
const contract_address = "0x63865E0F065C7b865e1a2EE4d99C383A414Bec22";


app.post("/register", function(req, res){
    var newUser = req.body.username;
    var account = req.body.account;
    req.session.currentUser = account;

    MyContract.at(contract_address).then(function(instance) {

        return instance.registerUser.sendTransaction(newUser, {from: account});

    }).then(function(result) {
        console.log(result);

        res.render("dashboard", {name: newUser, account: account});

    }).catch(function(error) {
        console.log(error);
        res.redirect("/");
    });
});

I am getting this ERROR on sendTransaction -

Error: Returned error: The method eth_sendTransaction does not exist/is not available\n    at Object.ErrorResponse (...\\node_modules\\web3-core-helpers\\src\\errors.js:29:16)\n    at ...\\node_modules\\web3-core-requestmanager\\src\\index.js:140:36\n    at XMLHttpRequest.request.onreadystatechange (...\\node_modules\\web3\\node_modules\\web3-providers-http\\src\\index.js:110:13)\n    at XMLHttpRequestEventTarget.dispatchEvent (...\\node_modules\\xhr2-cookies\\dist\\xml-http-request-event-target.js:34:22)\n    at XMLHttpRequest._setReadyState ...\\node_modules\\xhr2-cookies\\dist\\xml-http-request.js:208:14)\n    at XMLHttpRequest._onHttpResponseEnd (...\\node_modules\\xhr2-cookies\\dist\\xml-http-request.js:318:14)\n    at IncomingMessage.<anonymous> (...\\node_modules\\xhr2-cookies\\dist\\xml-http-request.js:289:61)\n    at IncomingMessage.emit (events.js:203:15)\n    at endReadableNT (_stream_readable.js:1145:12)\n    at process._tickCallback (internal/process/next_tick.js:63:19)'

I am using Metamask(v.7.7.8) and managing the account address via express-session. I know that Infura does not support sendTransaction but @truffle/contract does not support sendRawTransaction too. Please help me find an easier solution with @truffle/contract.

Answer 1

I have created and compiled a contract according to the one that you've posted in a comment.

I have deployed it to Ropsten, and then verified it on Etherscan.

As you can see on Etherscan, its byte-code contains the sequence 704f1b94, which is the function-selector of function registerUser(string).

And as you can see on Etherscan, the byte-code of your contract does not contain this function-selector, which means that your contract does not implement this function!

This by itself is a good enough reason for your transaction to revert.

A few technical notes:

1. You can generate the function-selector above by taking the first 4 bytes (8 hexadecimal characters) of the printout of console.log(Web3.utils.keccak256("registerUser(string)"));.

2. Here is the contract which I have compiled, deployed and verified on Etherscan:

pragma solidity 0.4.26;

contract MyContract {

    struct user {
        address id;
        string name;
    }

    uint internal totalUsers = 0;
    mapping(address => user) internal users;

    function registerUser(string memory name) public {
        user storage u = users[msg.sender];
        require(keccak256(abi.encodePacked((name))) != keccak256(abi.encodePacked((""))));
        if(msg.sender == u.id) {
            revert("already registered");
        } else {
            users[msg.sender] = user(msg.sender, name);
            totalUsers++;
        }
    }
}

3. Here is the NodeJS script which I have used for testing the contract function:

const Web3 = require("web3");

const PROJECT_ID  = process.argv[2];
const PRIVATE_KEY = process.argv[3];

const ABI  = [{"type":"function","name":"registerUser","inputs":[{"name":"name","type":"string","internalType":"string"}],"outputs":[],"stateMutability":"nonpayable","constant":false,"payable":false}];
const ADDR = "0x6285F7CC0cD9D4E5DBB81353276DCc099fa9C6B9";

async function send(web3, account, transaction, value = 0) {
    const options = {
        to      : transaction._parent._address,
        data    : transaction.encodeABI(),
        gas     : await transaction.estimateGas({from: account.address}),
        gasPrice: await web3.eth.getGasPrice(),
        value   : value
    };
    const signed  = await web3.eth.accounts.signTransaction(options, account.privateKey);
    const receipt = await web3.eth.sendSignedTransaction(signed.rawTransaction);
    return receipt;
}

async function run() {
    const web3     = new Web3("https://ropsten.infura.io/v3/" + PROJECT_ID);
    const contract = new web3.eth.Contract(ABI, ADDR);
    const account  = web3.eth.accounts.privateKeyToAccount(PRIVATE_KEY);
    const receipt  = await send(web3, account, contract.methods.registerUser("myName"));
    console.log(receipt);
}

run();

Answer 2

It seems you are using your contract from the backend. In that case you cannot use MetaMask because it runs in the browser.

You have these options:

• Execute the transactions that make changes from the frontend. The UI has to connect to MetaMask and use it as provider for @truffle/contract.

• Use your own wallet in the backend and configure truffle to use it as provider. For example you can use HDWallet Provider.