Add support for custom compiler version

Currently, the version ^0.3.5 of solc is used. The solidity compiler does not produce the same results depending on the on the version used. Dapp developpers may want to control which version is used.

The ability to provide a custom version in the config/as option would be great. Then use this version while invoking the solidity compiler as: var solcV011 = solc.useVersion('v0.1.1-2015-08-04-6ff4cd6');

[chevdor]

Actually, the main reason is not only 0.4.x but exactly what you mentioned about the downgrading.

Compilers do not behave the same, so while it is advised using the latest, sometimes, people prefer to use a given (older) version.

The 0.4.x example you mention is a good one, we should use 0.4.x, but for now we don´t (whatever the reasons are).

I think it would be fair to have such feature, and as you suggest, lock it down, at least for now, to a given set of versions (ie everything < 0.4.x)

To avoid any extra issue reports, I would specifically point to this ticket since you now nicely explained why 0.4.x cannot yet be working 😃

[tcoulter]

In general I see this as a good feature. However, I’d guess you want this feature so you can bump the version up to solidity 0.4.x, right? If so, this solution will likely cause more problems than it solves.

The main reason Truffle hasn’t been bumped up to version 0.4.x already is because of the introduction of breaking changes: Specifically the pragma statement. This is an issue because Truffle uses a library called solidity-parser in order to perform some preprocessing, and solidity-parser needs to be upgraded to support the pragma statement before you can use 0.4.x with Truffle. If you were to use the proposed feature to upgrade the version to 0.4.x, Truffle will error before compilation ever occurs.

Where this feature could be very useful is downgrading the compiler version, or setting a specific compiler version for testing purposes (aka, testing the compiler) or locking your project into a specific version. But it won’t be able to go forward past the latest version Truffle supports (0.3.5 in this case). If we implement this feature, we need to ensure we don’t allow users to go higher than the latest version supported as that will cause unexpected errors.

To better understand your use case, why do you want to specify the version?