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Using Foundry to Deploy To Moonbeam

Foundry Create Project

Introduction

Foundry is an Ethereum development environment written in Rust that helps developers manage dependencies, compile projects, run tests, deploy contracts, and interact with blockchains from the command line. Foundry can directly interact with Moonbeam's Ethereum API so it can be used to deploy smart contracts into Moonbeam.

There are four tools that make up Foundry:

  • Forge - compiles, tests, and deploys contracts
  • Cast - a command line interface for interacting with contracts
  • Anvil - a local TestNet node for development purposes that can fork preexisting networks
  • Chisel - a Solidity REPL for quickly testing Solidity snippets

This guide will cover how to use Foundry to compile, deploy, and debug Ethereum smart contracts on the Moonbase Alpha TestNet. This guide can also be adapted for Moonbeam, Moonriver, or a Moonbeam development node.

Checking Prerequisites

To get started, you will need the following:

  • Have an account with funds. You can get DEV tokens for testing on Moonbase Alpha once every 24 hours from the Moonbase Alpha Faucet
  • To test out the examples in this guide on Moonbeam or Moonriver, you will need to have your own endpoint and API key, which you can get from one of the supported Endpoint Providers.
  • Have Foundry installed

Creating a Foundry Project

You will need to create a Foundry project if you don't already have one. You can create one by completing the following steps:

  1. Install Foundry if you haven't already. If on Linux or MacOS, you can run these commands:

    curl -L https://foundry.paradigm.xyz | bash
foundryup

    If on Windows, you'll have to install Rust & then build Foundry from source:

    curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs/ | sh
cargo install --git https://github.com/foundry-rs/foundry foundry-cli anvil --bins --locked

  2. Create the project, which will create a folder with three folders within it: 

    forge init foundry

With the default project created, you should see three folders.

  • lib - all of the project's dependencies in the form of git submodules
  • src - where to put your smart contracts (with functionality)
  • test - where to put the forge tests for your project, which are written in Solidity

In addition to these three folders, a git project will also be created along with a prewritten .gitignore file with relevant file types and folders ignored.

The Source Folder

The src folder may already contain Contract.sol, a minimal Solidity contract. Feel free to delete it. Instead, you will be deploying an ERC-20 contract. In the contracts directory, you can create the MyToken.sol file:

cd src
touch MyToken.sol

Open the file and add the following contract to it:

pragma solidity ^0.8.0;

// Import OpenZeppelin Contract
import "openzeppelin-contracts/contracts/token/ERC20/ERC20.sol";

// This ERC-20 contract mints the specified amount of tokens to the contract creator
contract MyToken is ERC20 {
  constructor(uint256 initialSupply) ERC20("MyToken", "MYTOK") {
    _mint(msg.sender, initialSupply);
  }
}

Before you attempt to compile, install OpenZeppelin contracts as a dependency. You may have to commit previous changes to git beforehand. By default, Foundry uses git submodules instead of npm packages, so the traditional npm import path and command are not used. Instead, use the name of OpenZeppelin's Github repository:

forge install OpenZeppelin/openzeppelin-contracts

Compiling Solidity

Once all dependencies have been installed, you can compile the contract:

forge build

Foundry Contract Compile

After compilation, two folders will be created: out and cache. The ABI and bytecode for your contracts will be contained within the out folder. These two folders are already ignored by the .gitignore included in the default Foundry project initialization.

Deploying the Contract

Deploying the contract with Forge takes a single command, but you will need to include an RPC endpoint, a funded private key, and constructor arguments. MyToken.sol asks for an initial supply of tokens in its constructor, so each of the following commands include 100 as a constructor argument. You can deploy the MyToken.sol contract using the command for the correct network:

forge create --rpc-url INSERT_RPC_API_ENDPOINT \
--constructor-args 100 \
--private-key YOUR_PRIVATE_KEY \
src/MyToken.sol:MyToken

forge create --rpc-url INSERT_RPC_API_ENDPOINT \
--constructor-args 100 \
--private-key YOUR_PRIVATE_KEY \
src/MyToken.sol:MyToken

forge create --rpc-url https://rpc.api.moonbase.moonbeam.network \
--constructor-args 100 \
--private-key YOUR_PRIVATE_KEY \
src/MyToken.sol:MyToken

forge create --rpc-url http://127.0.0.1:9944 \
--constructor-args 100 \
--private-key YOUR_PRIVATE_KEY \
src/MyToken.sol:MyToken

Note

If you run into the following error while trying to deploy the contract, you may need to customize your foundry.toml file:

(code: -32603, message: evm error: InvalidCode(Opcode(95)), data: Some(String("0x")))

With the release of Solidity v0.8.20, support for the Shanghai hard fork has been introduced, which includes PUSH0 opcodes in the generated bytecode. Support for the PUSH0 opcode on Moonbeam hasn't been rolled out yet. As such, if you'd like to use Solidity v0.8.20, you'll need to add an additional configuration in your foundry.toml file to use the London compiler:

solc_version = '0.8.20'
evm_version = 'london'

After a few seconds, the contract is deployed, and you should see the address in the terminal.

Foundry Contract Deploy

Congratulations, your contract is live! Save the address, as you will use it to interact with this contract instance in the next step.

Interacting with the Contract

Foundry includes cast, a CLI for performing Ethereum RPC calls.

Try to retreive your token's name using cast, where YOUR_CONTRACT_ADDRESS is the address of the contract that you deployed in the previous section:

cast call YOUR_CONTRACT_ADDRESS "name()" --rpc-url INSERT_RPC_API_ENDPOINT

cast call YOUR_CONTRACT_ADDRESS "name()" --rpc-url INSERT_RPC_API_ENDPOINT

cast call YOUR_CONTRACT_ADDRESS "name()" --rpc-url https://rpc.api.moonbase.moonbeam.network

cast call YOUR_CONTRACT_ADDRESS "name()" --rpc-url http://127.0.0.1:9944

You should get this data in hexidecimal format: 

0x000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000074d79546f6b656e00000000000000000000000000000000000000000000000000

This is far from readable, but you can use cast to convert it into your desired format. In this case, the data is text, so you can convert it into ascii characters to see "My Token":

Foundry Contract View

cast --to-ascii 0x000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000074d79546f6b656e00000000000000000000000000000000000000000000000000

You can also mutate data with cast as well. Try burning tokens by sending them to the zero address.

cast send --private-key YOUR_PRIVATE_KEY \
--rpc-url INSERT_RPC_API_ENDPOINT \
--chain 1284 \
YOUR_CONTRACT_ADDRESS \
"transfer(address,uint256)" 0x0000000000000000000000000000000000000001 1

cast send --private-key YOUR_PRIVATE_KEY \
--rpc-url INSERT_RPC_API_ENDPOINT \
--chain 1285 \
YOUR_CONTRACT_ADDRESS \
"transfer(address,uint256)" 0x0000000000000000000000000000000000000001 1

cast send --private-key YOUR_PRIVATE_KEY \
--rpc-url https://rpc.api.moonbase.moonbeam.network \
--chain 1287 \
YOUR_CONTRACT_ADDRESS \
"transfer(address,uint256)" 0x0000000000000000000000000000000000000001 1

cast send --private-key YOUR_PRIVATE_KEY \
--rpc-url http://127.0.0.1:9944 \
--chain 1281 \
YOUR_CONTRACT_ADDRESS \
"transfer(address,uint256)" 0x0000000000000000000000000000000000000001 1

The transaction will be signed by your Moonbase account and be broadcasted to the network. The output should look similar to:

Foundry Contract Interaction

Congratulations, you have successfully deployed and interacted with a contract using Foundry!

Forking with Anvil

As previously mentioned, Anvil is a local TestNet node for development purposes that can fork preexisting networks. Forking Moonbeam allows you to interact with live contracts deployed on the network.

There are some limitations to be aware of when forking with Anvil. Since Anvil is based on an EVM implementation, you cannot interact with any of the Moonbeam precompiled contracts and their functions. Precompiles are a part of the Substrate implementation and therefore cannot be replicated in the simulated EVM environment. This prohibits you from interacting with cross-chain assets on Moonbeam and Substrate-based functionality such as staking and governance.

To fork Moonbeam or Moonriver, you will need to have your own endpoint and API key which you can get from one of the supported Endpoint Providers.

To fork Moonbeam from the command line, you can run the following command from within your Foundry project directory:

anvil --fork-url INSERT_RPC_API_ENDPOINT

anvil --fork-url INSERT_RPC_API_ENDPOINT

anvil --fork-url https://rpc.api.moonbase.moonbeam.network

Your forked instance will have 10 development accounts that are pre-funded with 10,000 test tokens. The forked instance is available at http://127.0.0.1:8545/. The output in your terminal should resemble the following:

Forking terminal screen

To verify you have forked the network, you can query the latest block number:

curl --data '{"method":"eth_blockNumber","params":[],"id":1,"jsonrpc":"2.0"}' -H "Content-Type: application/json" -X POST localhost:8545

If you convert the result from hex to decimal, you should get the latest block number from the time you forked the network. You can cross reference the block number using a block explorer.

From here you can deploy new contracts to your forked instance of Moonbeam or interact with contracts already deployed. Building off of the previous example in this guide, you can make a call using Cast to check the balance of the minted MYTOK tokens in the account you deployed the contract with:

cast call INSERT-CONTRACT-ADDRESS  "balanceOf(address)(uint256)" INSERT-YOUR-ADDRESS --rpc-url http://localhost:8545

Using Chisel

Chisel is a Solidity REPL, or shell. It allows a developer to write Solidity directly in the console for testing small snippets of code, letting developers skip the project setup and contract deployment steps for what should be a quick process.

Since Chisel is mainly useful for quick testing, it can be used outside of a Foundry project. But, if executed within a Foundry project, it will keep the configurations within foundry.toml when running.

For this example, you will be testing out some of the features of abi within Solidity because it is complex enough to demonstrate how Chisel could be useful. To get started using Chisel, run the following in the command line to start the shell:

chisel

In the shell, you can write Solidity code as if it was running within a function:

bytes memory myData = abi.encode(100, true, "Develop on Moonbeam");

Let's say you were interested in how abi encoded data, because you're looking into how to most efficiently store data on the blockchain and thus save gas. To view how the myData is stored in memory, you can use the following command while in the Chisel shell: 

!memdump

memdump will dump all of the data in your current session. You'll likely see something like this below. If you aren't good at reading hexadecimal or if you don't know how ABI encoding works, then you might not be able to find where the myData variable has been stored.

memdump in Chisel

Fortunately, Chisel lets you easily figure out where this information is stored. Using the !rawstack command, you can find the location in the stack where the value of a variable: 

!rawstack myData

In this situation, since bytes is over 32 bytes in length, the memory pointer is displayed instead. But that's exactly what's needed, since you already know the entirety of the stack from the !memdump command.

rawstack in Chisel

The !rawstack command shows that the myData variable is stored at 0x80, so when comparing this with the memory dump retrieved form the !memdump command, it looks like myData is stored like this: 

[0x80:0xa0]: 0x00000000000000000000000000000000000000000000000000000000000000a0
[0xa0:0xc0]: 0x0000000000000000000000000000000000000000000000000000000000000064
[0xc0:0xe0]: 0x0000000000000000000000000000000000000000000000000000000000000001
[0xe0:0x100]: 0x0000000000000000000000000000000000000000000000000000000000000060
[0x100:0x120]: 0x0000000000000000000000000000000000000000000000000000000000000013
[0x120:0x140]: 0x446576656c6f70206f6e204d6f6f6e6265616d00000000000000000000000000

At first glance this makes sense, since 0xa0 has a value of 0x64 which is equal to 100, and 0xc0 has a value of 0x01 which is equal to true. If you want to learn more about how ABI-encoding works, the Solidity documentation for ABI is helpful. In this case, there are a lot of zeros in this method of data packing, so as a smart contract developer you might instead try to use structs or pack the data together more efficiently with bitwise code.

Since you're done with this code, you can clear the state of Chisel so that it doesn't mess with any future logic that you want to try out (while running the same instance of Chisel): 

!clear

There's an even easier way to test with Chisel. When writing code that ends with a semicolon, ;, Chisel will run them as a statement, storing its value in Chisel's runtime state. But if you really only needed to see how the ABI-encoded data was represented, then you could get away with running the code as an expression. To try this out with the same abi example, write the following in the Chisel shell: 

abi.encode(100, true, "Develop on Moonbeam")

You should see something like the following:

Expressions in Chisel

While it doesn't display the data in the same way, you still get the contents of the data, and it also further breaks down how the information is coded, such as letting you know that the 0xa0 value defines the length of the data.

By default, when you leave the Chisel shell, none of the data is persisted. But you can instruct chisel to do so. For example, you can take the following steps to store a variable:

  1. Store a uint256 in Chisel 

    uint256 myNumber = 101;

  2. Store the session with !save. For this example, you can use the number 1 as a save ID 

    !save 1

  3. Quit the session

    !quit

Then to view and interact with your stored Chisel states, you can take the following steps:

  1. View a list of saved Chisel states 

    chisel list

  2. Load your stored states 

    chisel load

  3. View the uint256 saved in Chisel from the previous set of steps 

    !rawstack myNumber

Saving state in Chisel

You can even fork networks while using Chisel:

!fork https://rpc.api.moonbase.moonbeam.network

Then, for example, you can query the balance of one of Moonbase Alpha's collators: 

0x4c5A56ed5A4FF7B09aA86560AfD7d383F4831Cce.balance

Forking in Chisel

If you want to learn more about Chisel, download Foundry and refer to its official reference page.

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Last update: May 12, 2023
| Created: July 25, 2022