feat: make Script safer

[ZeroEkkusu]

Motivation

Fix #78

Note: Merging into v0.3

Solution

Changes

• Add stdStorageSafe without checked_write
• Add CheatsSafe with only deployCode
• Add VmSafe with only read-only cheatcodes
• Update Script
• Make all components abstract
• Update deployCode tests

Notes

• stdStorage delegates some functions to stdStorageSafe. This solution works for Solidity 0.6.0 and requires minimal code duplication:

stdStorageSafe {
    safeFun() {
        implementation
    }
}

stdStorage {
    safeFun() {
        return stdStorageSafe.safeFun()
    }

    unsafeFun() {
        implementation
    }
}

• Interfaces cannot inherit in Solidity 0.6.0, so, VmSafe contains duplicate code. Someone should check if I removed any necessary cheatcodes in VmSafe.

Breaking changes

• Only Cheats from CheatsSafe will be accessible in Script by default
• Only cheatcodes from VmSafe will be accessible from vm in Script by default

Link #139

[gakonst]

Should this inherit from VmSafe? Or it cannot because of older solidity?

[mds1]

Looks like interface inheritance was introduced in 0.6.2 https://github.com/ethereum/solidity/blob/develop/Changelog.md#062-2020-01-27

A bit hacky, but if we need to support versions older than 0.6.2 and don't want to duplicate code, we could probably make Vm and VmSafe abstract contracts instead of interfaces

[mds1]

Looks like the pragma on master is pragma solidity >=0.6.0 <0.9.0;. Based on the changelog, I'd be surprised if anyone needed 0.6.0 or 0.6.1 and can't bump to 0.6.2, so I think bumping that pragma to enable interface inheritance is safe.

I know some Maker repos are on 0.6.x, but from a quick search it looks like they use ^0.6.12 so no issues there:

• https://github.com/makerdao/dss-psm/search?q=pragma
• https://github.com/makerdao/dss/search?q=pragma

[mds1]

PR looks good to me overall 👌

Only Cheats from CheatsSafe will be accessible in Script by default

Only cheatcodes from VmSafe will be accessible from vm in Script by default

Where do you inherit from if you want all cheats in a script?

[ZeroEkkusu]

Where do you inherit from if you want all cheats in a script?

For Cheats:

contract MyScript is Script, Cheats {

For cheatcodes:

contract MyScript is Script {
      Vm internal constant VM = Vm(VM_ADDRESS);

You cannot name it vm, so this is up for discussion.

[mds1]

Got it, seems reasonable. Also should we rename to StdCheats[Safe] and StdAssertions? That naming fits with stdStorage, stdMath, etc., and makes it easier to different StdCheats (forge-std helpers) from cheatcodes (native forge cheatcodes), whereas IMO "Cheats" vs "cheatcodes" is an easy-to-confuse distinction. The files could all be renamed accordingly too for clarity (open to doing this in a separate PR, just thought of it since the above was a bit confusing)

[ZeroEkkusu]

I'll add those ideas to our todo.