Configuration

Eclair can be used without any configuration but it is possible to configure it to make the experience smoother. Eclair will also load Foundry's configuration which can be used for some settings such as the RPC URL and the Etherscan API key. Using the global configuration at ~/.foundry/foundry.toml can be convenient for such settings.

A sample Foundry configuration file can be found in the config directory.

RPC URL

The RPC url can be configured in several ways:

• Using the ETH_RPC_URL environment variable
• Using the --rpc-url option in the command line
• Using the vm.rpc(RPC_URL) function inside a session

Using Foundry configuration file

The rpc_endpoints section of foundry.toml to set aliases for your RPC URLs. Here is a sample configuration:

# ~/.foundry/foundry.toml
[rpc_endpoints]
mainnet = "https://eth.llamarpc.com"
optimism = "https://mainnet.optimism.io"

This then allows to use vm.rpc("mainnet") or vm.rpc("optimism") to connect to the respective networks.

Etherscan API Key

Eclair requires an Etherscan API key to fetch contract ABIs and interact with the Etherscan API. The API key can be set using the ETHERSCAN_API_KEY environment variable, which will be available for all chains. For a per-chain configuration, the following environment variables can be used:

• Ethereum: ETHERSCAN_API_KEY
• Optimism: OP_ETHERSCAN_API_KEY
• Gnosis Chain: GNOSISSCAN_API_KEY
• Polygon: POLYGONSCAN_API_KEY
• Polygon zkEVM: POLYGONSCAN_ZKEVM_API_KEY
• Base: BASESCAN_API_KEY
• Arbitrum: ARBISCAN_API_KEY
• Sepolia: SEPOLIA_ETHERSCAN_API_KEY

Using Foundry configuration file

The etherscan section of foundry.toml can be used to set the API key for different chains.

Here is a sample configuration:

# ~/.foundry/foundry.toml
[etherscan]
mainnet = { key = "ETHERSCAN_API_KEY" }
optimism = { key = "OP_ETHERSCAN_API_KEY" }

Initial setup

To allow to load common contracts and perform any other setup, Eclair can be configured to run code at startup. By default, Eclair will look for a file named .eclair_init.sol in the current directory as well as in the $HOME/.foundry directory. Eclair will look for a function called setUp and load everything defined there in the current environment. Note that any function defined will be loaded as normal functions and can be called from the REPL.

Here is an example setup:

function setUp() {
    abi.load("ERC20", "~/.foundry/abis/erc20.json");

    if (!vm.connected) return;

    chainid = block.chainid;
    if (chainid == 1) {
        usdc = ERC20(0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48);
    } else if (chainid == 10) {
        usdc = ERC20(0x0b2c639c533813f4aa9d7837caf62653d097ff85);
    }
}