Deploying and Verifying

Deploying

Forge can deploy smart contracts to a given network with the forge create command.

Forge can deploy only one contract at a time.

To deploy a contract, you must provide a RPC URL (env: ETH_RPC_URL) and the private key of the account that will deploy the contract.

To deploy MyContract to a network:

$ forge create --rpc-url <your_rpc_url> --private-key <your_private_key> src/MyContract.sol:MyContract
compiling...
success.
Deployer: 0xa735b3c25f...
Deployed to: 0x4054415432...
Transaction hash: 0x6b4e0ff93a...

Solidity files may contain multiple contracts. :MyContract above specifies which contract to deploy from the src/MyContract.sol file.

Use the --constructor-args flag to pass arguments to the constructor:

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

import {ERC20} from "solmate/tokens/ERC20.sol";

contract MyToken is ERC20 {
    constructor(
        string memory name,
        string memory symbol,
        uint8 decimals,
        uint256 initialSupply
    ) ERC20(name, symbol, decimals) {
        _mint(msg.sender, initialSupply);
    }
}

Additionally, we can tell Forge to verify our contract on Etherscan, if the network is supported, by passing --verify.

$ forge create --rpc-url <your_rpc_url> \
    --constructor-args "ForgeUSD" "FUSD" 18 1000000000000000000000 \
    --private-key <your_private_key> src/MyToken.sol:MyToken \
    --etherscan-api-key <your_etherscan_api_key> \
    --verify

Verifying a pre-existing contract

It is recommended to use the --verify flag with forge create to automatically verify the contract on Etherscan after a deployment. Note that ETHERSCAN_API_KEY must be set.

If you are verifying an already deployed contract, read on.

You can verify a contract on Etherscan with the forge verify-contract command.

You must provide:

the contract address
the path to the contract <path>:<contractname>
your Etherscan API key (env: ETHERSCAN_API_KEY).

Moreover, you may need to provide:

compiler version used for build, with 8 hex digits from the commit version prefix (the commit will usually not be a nightly build). It is auto-detected if not specified.
the constructor arguments in the ABI-encoded format, if there are any
the number of optimizations, if the Solidity optimizer was activated. It is auto-detected if not specified.
the chain ID, if the contract is not on Ethereum Mainnet

Let's say you want to verify MyToken (see above). You set the number of optimizations to 1 million, compiled it with v0.8.10, and deployed it, as shown above, to the Kovan testnet (chain ID: 42). Note that --num-of-optimizations will default to 0 if not set on verification, while it defaults to 200 if not set on deployment, so make sure you pass --num-of-optimizations 200 if you left the default compilation settings.

Here's how to verify it:

$ forge verify-contract --chain-id 42 --num-of-optimizations 1000000 --constructor-args \ 
    $(cast abi-encode "constructor(string,string,uint256,uint256)" "ForgeUSD" "FUSD" 18 1000000000000000000000) \
    --compiler-version v0.8.10+commit.fc410830 <the_contract_address> src/MyToken.sol:MyToken <your_etherscan_api_key>

Submitted contract for verification:
                Response: `OK`
                GUID: `a6yrbjp5prvakia6bqp5qdacczyfhkyi5j1r6qbds1js41ak1a`
                url: https://kovan.etherscan.io//address/0x6a54…3a4c#code

You can check verification status with the forge verify-check command:

$ forge verify-check --chain-id 42 <GUID> <your_etherscan_api_key>
Contract successfully verified.

💡 Tip

Use Cast's abi-encode to ABI-encode arguments.

In this example, we ran cast abi-encode "constructor(string,string,uint8,uint256)" "ForgeUSD" "FUSD" 18 1000000000000000000000 to ABI-encode the arguments.

Troubleshooting

`Invalid character 'x' at position 1`

Make sure the private key string does not begin with 0x.

`EIP-1559 not activated`

EIP-1559 is not supported or not activated on the RPC server. Pass the --legacy flag to use legacy transactions instead of the EIP-1559 ones. If you do development in a local environment, you can use Hardhat instead of Ganache.

`Failed to parse tokens`

Make sure the passed arguments are of correct type.

`Signature error`

Make sure the private key is correct.

`Compiler version commit for verify`

If you want to check the exact commit you are running locally, try: ~/.svm/0.x.y/solc-0.x.y --version where x and y are major and minor version numbers respectively. The output of this will be something like:

solc, the solidity compiler commandline interface
Version: 0.8.12+commit.f00d7308.Darwin.appleclang

Note: You cannot just paste the entire string "0.8.12+commit.f00d7308.Darwin.appleclang" as the argument for the compiler-version. But you can use the 8 hex digits of the commit to look up exactly what you should copy and paste from compiler version.

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