Why does the solidity compiler throw a parse error on import statements? What's the workaround?

Question

I used npm install to install my node package dependencies. My node package dependencies look like the following:

  "dependencies": {
    "blockcypher": "^0.2.0",
    "fs-extra": "^7.0.1",
    "ganache-cli": "^6.2.4",
    "mocha": "^5.2.0",
    "openzeppelin-solidity": "^2.0.0",
    "solc": "^0.4.24"
  }

When I run the following compile script using node I get the following error within EVERY contract that has an import statement that references dependency in my node_modules.

I'm using Solidity Version: ^0.4.24

Solidity Error: ParseError: Source "node_modules/openzeppelin-solidity/ect.." not found

const path = require("path"); //Delete all the contents in the build folder
const solc = require("solc"); //solidity compiler
const fs = require("fs-extra"); // Gives us access to the file system

//Require The Import Statements From The Contract
// import "node_modules/openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";
// import "node_modules/openzeppelin-solidity/contracts/ownership/Ownable.sol";
// import "node_modules/openzeppelin-solidity/contracts/token/ERC20/IERC20.sol";

//var data = require("node_modules/openzeppelin-solidity/contracts/token/ERC20/ERC20.json");
//How do I use this?

const buildPath = path.resolve(__dirname, "build");
fs.removeSync(buildPath);

const campainPath = path.resolve(__dirname, "Contract.sol");
// const campainPath = path.resolve(__dirname, "contracts", "Esgro.sol");
const source = fs.readFileSync(campainPath, "utf8");

console.log("\n\n\t Compilation Output \n\n\n");
console.log(solc.compile(source, 1));
const output = solc.compile(source, 1).contracts; //Internal Error
console.log("\n\n\t Compilation Output \n\n\n");
console.log(output);

fs.ensureDirSync(buildPath);

for (let contract in output) {
  // fs.outputJsonSync(
  //   path.resolve(buildPath, contract.replace(":"", "") + ".json"),
  //   output[contract]
  // );

  console.log("\n\n\t output[contract] \n\n\n");
  console.log(output[contract]);

  fs.outputJsonSync(path.resolve(buildPath, contract), output[contract]);
}

//Compile both contracts with the solc compiler

//Write the output to the build directory

How do you get the compiler to "connect" with the third party dependencies on a local machine? Any help or pointers would be greatly appreciated.

Stefano Stefano · Accepted Answer · 2019-01-16T13:37:42

the correct syntax for importing an npm dependency into a .sol file is the follows:

import "openzeppelin-solidity/contracts/token/ERC20/ERC20Mintable.sol"; //You don't need to write node_modules

openzeppelin's documentation says:

You need an ethereum development framework for the above import statements to work!

so, probably is better that you use Truffle or Embark to compile and migrate your contract.

One last thing, OpenZeppelin uses the version ^ 0.5.0 of solidity, so when you go to compile remember to use a suitable version of solc.

Let me know if it worked

Why does the solidity compiler throw a parse error on import statements? What's the workaround?

1 Answers