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How to deploy a smart contract to Celo testnet, Mainnet, or a local network using Foundry.

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Introduction to Foundry

Foundry is a smart contract development toolchain. Foundry manages your dependencies, compiles your project, runs tests, deploys, and lets you interact with the chain from the command-line and via Solidity scripts.

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Prerequisites

You will need the Rust compiler and Cargo, the Rust package manager. The easiest way to install both is with rustup.rs.

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Using Foundryup

Foundryup is the Foundry toolchain installer. You can find more about it here. Open your terminal and run the following command: 
curl -L https://foundry.paradigm.xyz | bash
This will install Foundryup, then simply follow the instructions on-screen, which will make the foundryup command available in your CLI. Running foundryup by itself will install the latest (nightly) precompiled binaries: forge, cast, anvil, and chisel.

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Create a new project using Forge

To start a new project with Foundry, use: 
forge init hello_foundry
If you initializing project in an already initialized git repo use:
forge init project_name --no-git

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Adding a dependency

To add a dependency, use: 
forge install openzeppelin/openzeppelin-contracts

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Remapping dependencies

Forge can remap dependencies to make them easier to import. Forge will automatically try to deduce some remappings for you 
$ forge remappings

ds-test/=lib/solmate/lib/ds-test/src/
forge-std/=lib/forge-std/src/
solmate/=lib/solmate/src/
weird-erc20/=lib/weird-erc20/src/
These remappings mean:
  • To import from forge-std we would write: import forge-std/Contract.sol;
  • To import from ds-test we would write: import ds-test/Contract.sol;
  • To import from solmate we would write: import solmate/Contract.sol;
  • To import from weird-erc20 we would write: import weird-erc20/Contract.sol;
You can customize these remappings by creating a remappings.txt file in the root of your project.

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Removing dependencies

You can remove dependencies using 
forge remove openzeppelin/openzeppelin-contracts

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Adding Celo specific config to foundry.toml

Add the following configuration to foundry.toml file in the root level of your project. 
[rpc_endpoints]
celo-sepolia = "https://forno.celo-sepolia.celo-testnet.org/"
celo = "https://forno.celo.org"

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Deploying contract

Forge can deploy smart contracts to a given network using: The below example deploys Counter contract at location src/Counter.sol in the project to the Celo Sepolia Testnet. 
forge create --rpc-url celo-sepolia --private-key <your_private_key> src/Counter.sol:Counter
Notice the contract name after :, this is because a single solidity file can have multiple contracts.It is recommended to use --verify flag so that the contract gets verified right after deployment, this requires etherscan configuration in the foundry.toml file.
On successful deployment, you should a following output!
github
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