[Ethereum] How to specify a different Solidity version in a Truffle contract

contract-developmentsoliditytruffle

I've got a contract where I want to use <address>.transfer(), which was released in the latest Solidity version 0.4.10.

I have as the first line of my contract: pragma solidity 0.4.10; but when I compile I get Error: Source file requires different compiler version which pretty obviously means truffle is trying to compile my contract with not that version of Solidity. It still uses 0.4.8.

I installed 0.4.10 last night and solc --version shows 0.4.10.

So my question is, how do I change the version of Solidity in a truffle project? I've looked in the config file and the truffle docs and could not find this. I also cannot even find where 0.4.8 is installed (was assuming in truffle itself but it is not listed in truffle's package.json).

Best Answer

In Truffle version 5.0.0 (currently in Beta) you can specify a Solidity version in the truffle.js config file eg

module.exports = {
  networks: {
    ... etc ...
  },
  compilers: {
     solc: {
       version: <string>  // ex:  "0.4.20". (Default: Truffle's installed solc)
     }
  }
};

This is copied from the release details here

Related Solutions

[Ethereum] Truffle Compile with Solidity 0.5.0

I managed to solve this by uninstalling and reinstalling nvm and node and then uninstalling and reinstalling truffle@beta. It could be that for some reason something was installed wrong (or didn't work with a later version) therefore creating the problem.

Solidity Compiler Issue – Source File Requires Different Version

During solidity (solc) 0.5 releases the different frameworks like solc, truffle, web3, openzeppelin had a timeframe where some had a 0.5 compatible version released and some didn't. I think you could have changed specified the solc version like here (didn't try that) but meanwhile all of the mentioned fully support 0.5 (openzeppelin since 2 days ago at time of writing).

Consider doing the following

npm outdated
npm install [my-outdated-package] #repeat for all outdated packages
rm -R -f build #cleanup step (might not be necessary)
rm -R -f node_modules #cleanup step (might not be necessary)
npm install
truffle compile #(will still fail)

Check with truffle version in a terminal window at some other place (not project dir) if it matches the current release here otherwise do this:

npm uninstall -g truffle
npm install truffle

Usually you should avoid installing global packages but e.g. BlockCatIO/solidity-flattener requires that solc is installed globally because of certain features (installation described here). Remember to upgrade that one too.

When you then run truffle-compile you should still see errors because they changed the syntax of pragma (found that here).

So change:

#old
pragma solidity ^0.4.20;

#new
pragma solidity >=0.4.20;

I also recommend upgrading ganache-cli (I had problems running the tests with old version):

npm install -g ganache-cli

You might then still see compile errors but that's what makes v0.5 great because they made some improvements you should troubleshoot one-by-one

Here the Breaking Changes in Solidity 0.5.0

Doing this I got it compiling again :)

Best Answer

Related Solutions

[Ethereum] Truffle Compile with Solidity 0.5.0

Solidity Compiler Issue – Source File Requires Different Version

Related Topic