Unable to get abi and bytecode when compiling using solc

Question

I am new to solidity and am following a tutorial that uses solidity compiler version 0.4.25. In the tutorial, solc.compile is used in a compile.js file followed by extract abi and bytecode and generating json files by using the following codes:

const output = solc.compile(contractSource, 1);

for (let contract in output.contracts){
    fileSystem.outputJSONSync(
        path.resolve(exportPath,"Interface.json"),
        output.contracts[contract].interface
    );

    fileSystem.outputJSONSync(
        path.resolve(exportPath,"ByteCode.json"),
        output.contracts[contract].bytecode
    );
}

I am trying to compile a contract using solidity compiler version 0.5.3 instead and am able to get the output from the compiler by changing the codes to:

var input = {
    language: 'Solidity',
    sources: {
        'Voting.sol': {
            content: votingSource
        }
    },
    settings: {
        outputSelection: {
            '*': {
                '*': [ '*' ]
            }
        }
    }
}

const output = JSON.parse(solc.compile(JSON.stringify(input)),1);

However, I am unable to find the abi and bytecode using:

output.contracts[contract].interface
output.contracts[contract].bytecode

I think it is because the output structure is different from the output compiled using version 0.4.25 and that there isn't interface in the structure compiled using version 0.5.3. I would like to know what do I use instead to get the same json file outputs using the newer compiler version as well as how to get pass the error I encountered which I will show below.

I run compile.js in terminal and get the following error

TypeError: Cannot read property 'replace' of undefined at stringify (...\node_modules\fs-extra\node_modules\jsonfile\index.js:88:14) at Object.writeFileSync (...\node_modules\fs-extra\node_modules\jsonfile\index.js:115:13) at Object.outputJsonSync (...\node_modules\fs-extra\lib\json\output-json-sync.js:15:12) at Object. (...\smartContract\compile.js:35:20) at Module._compile (internal/modules/cjs/loader.js:722:30) at Object.Module._extensions..js (internal/modules/cjs/loader.js:733:10) at Module.load (internal/modules/cjs/loader.js:620:32) at tryModuleLoad (internal/modules/cjs/loader.js:560:12) at Function.Module._load (internal/modules/cjs/loader.js:552:3) at Function.Module.runMain (internal/modules/cjs/loader.js:775:12)

Here's my codes. Voting.sol

pragma solidity ^0.5.3;

contract Voting {

    address chairPersonAddress;

    struct Candidate {
        address candidateAddress;
        uint votes;
    }

    struct Vote{
        uint votedCandidateIndex;
        bool alreadyVoted;
    }

    modifier onlyChairPerson(){
        require(msg.sender == chairPersonAddress);
        _;
    }

    mapping(address => Vote) public voterAddressToTheirVote;

    Candidate[] public candidates;

    constructor(address _chairPersonAddress) public {
        chairPersonAddress = _chairPersonAddress;
    }

    function nominateCandidate(address _candidateAddress) onlyChairPerson public {
        Candidate memory newCandidate = Candidate({
            candidateAddress: _candidateAddress,
            votes: 0
        });

        candidates.push(newCandidate);
    }

    function vote(uint _candidateIndex) public {
        Vote memory existingVote = voterAddressToTheirVote[msg.sender];
        //If voter vote for the first candidate in the list - the index is always 0
        if(_candidateIndex == 0){
            require(existingVote.alreadyVoted == false, "You already voted for the first candidate");
            _addNewVote(_candidateIndex);
        }
        else{
            require(existingVote.votedCandidateIndex != _candidateIndex && existingVote.alreadyVoted == false, "You already voted for this candidate");
            _addNewVote(_candidateIndex);
        }
    }

    function _addNewVote(uint _candidateIndex) private {
        Vote memory newVote = Vote({
            votedCandidateIndex: _candidateIndex,
            alreadyVoted: true
        });

        voterAddressToTheirVote[msg.sender] = newVote;

        candidates[_candidateIndex].votes++;
    }

    function numberOfCandidates() public view returns(uint){
        return candidates.length;
    }
}

compile.js

const path = require("path");
const solc = require("solc");
const fileSystem = require("fs-extra");

//Preparing for bin folder
const exportPath = path.resolve(__dirname, "bin");
fileSystem.removeSync(exportPath);

//Get contract path
const votingContract = path.resolve(__dirname, "contracts", "Voting.sol");

//Read the contract from voting path
const votingSource = fileSystem.readFileSync(votingContract, "utf8");

var input = {
    language: 'Solidity',
    sources: {
        'Voting.sol': {
            content: votingSource
        }
    },
    settings: {
        outputSelection: {
            '*': {
                '*': [ '*' ]
            }
        }
    }
}

try{
    const output = JSON.parse(solc.compile(JSON.stringify(input)),1);

    for (let contract in output.contracts){
        fileSystem.outputJSONSync(
            path.resolve(exportPath,"VotingABI.json"),
            output.contracts[contract].interface
        );

        fileSystem.outputJSONSync(
            path.resolve(exportPath,"VotingBytecode.json"),
            output.contracts[contract].bytecode
        ); 
    }  

}catch(error){
    console.log(error);
}

Answer 1

Replace your for loop with this

    for (let contract in output.contracts["Voting.sol"]) {
    fileSystem.outputJSONSync(
      path.resolve(exportPath, "VotingABI.json"),
      output.contracts["Voting.sol"][contract].abi
    );

    fileSystem.outputJSONSync(
      path.resolve(exportPath, "VotingBytecode.json"),
      output.contracts["Voting.sol"][contract].evm.bytecode.object
    );
  }

For reference usage of solcjs , please check https://www.npmjs.com/package/solc

I strongly recommend using Truffle for compiling and deploying such contracts because it is easy and awesome.

Disclaimer - I work for Consensys

Answer 2

Solution to get the interface and bytecode:

• "solc": "^0.8.3",
• "web3": "^1.3.5"

const path = require('path');
const fs = require('fs');
const solc = require('solc');

const inboxPath = path.resolve(__dirname, 'contracts', 'inbox.sol');
const source = fs.readFileSync(inboxPath, 'utf-8');

var input = {
    language: 'Solidity',
    sources: {
        'inbox.sol' : {
            content: source
        }
    },
    settings: {
        outputSelection: {
            '*': {
                '*': [ '*' ]
            }
        }
    }
}; 

const output = JSON.parse(solc.compile(JSON.stringify(input)));

const interface = output.contracts['inbox.sol'].Inbox.abi;
const bytecode = output.contracts['inbox.sol'].Inbox.evm.bytecode.object;

module.exports = {
    interface,
    bytecode,
};

Answer 3

I have a simpler solution for accomplishing your task:

const fs = require('fs');
const solc = require('solc');
const input = fs.readFileSync('/path/to/.sol/file');
const output = solc.compile(input.toString(), 1);
const bytecode = output.contracts[':ContractName'].bytecode;
const abi = JSON.parse(output.contracts[':ContractName'].interface);

console.log('\nBytecode: ', bytecode, '\nABI: ', abi);

This will give you the bytecode and abi for your contract.

Answer 4

0.5.3 does not generate interface in JSON - I think docs say so ...

to get abi and bytecode from your newly formatted JSON - I do following JSON.stringify(compiledFactory.abi) compiledFactory.evm.bytecode