@avalabs/subnet-evm-contract-examples

Subnet EVM Contracts

CONTRACTS HERE ARE ALPHA SOFTWARE AND ARE NOT AUDITED. USE AT YOUR OWN RISK!

Introduction

Avalanche is an open-source platform for launching decentralized applications and enterprise blockchain deployments in one interoperable, highly scalable ecosystem. Avalanche gives you complete control on both the network and application layers—helping you build anything you can imagine.

The Avalanche Network is composed of many subnets and chains. Chains in subnets run with customizable virtual machines. One of these virtual machines is Subnet EVM. The Subnet EVM's API is almost identical to an Ethereum node's API. Subnet EVM brings its own features like minting native tokens via contracts, restrincting contract deployer etc. These features are presented with Stateful Precompile Contracts. These contracts are precompiled and deployed when they're activated.

The goal of this guide is to lay out best practices regarding writing, testing and deployment of smart contracts to Avalanche's Subnet EVM. We'll be building smart contracts with development environment Hardhat.

Prerequisites

NodeJS and NPM

First, install the LTS (long-term support) version of nodejs. This is 18.16.0 at the time of writing. NodeJS bundles npm.

Solidity and Avalanche

It is also helpful to have a basic understanding of Solidity and Avalanche.

Dependencies

Clone the repo and install the necessary packages via yarn.

$ git clone https://github.com/ava-labs/subnet-evm.git
$ cd contract-examples
$ npm install

Write Contracts

AllowList.sol is the base contract which provided AllowList precompile capabilities to inheriting contracts.

ERC20NativeMinter.sol is based on Open Zeppelin ERC20 contract powered by native minting capabilities of Subnet EVM. ERC20 is a popular smart contract interface. It uses INativeMinter interface to interact with NativeMinter precompile.

ExampleDeployerList shows how ContractDeployerAllowList precompile can be used in a smart contract. It uses IAllowList to interact with ContractDeployerAllowList precompile. When the precompile is activated only those allowed can deploy contracts.

ExampleFeeManager shows how a contract can change fee configuration with the FeeManager precompile.

All of these NativeMinter, FeeManager and AllowList contracts should be enabled by a chain config in genesis or as an upgrade. See the example genesis under Tests section.

For more information about precompiles see subnet-evm precompiles.

Hardhat Config

Hardhat uses hardhat.config.js as the configuration file. You can define tasks, networks, compilers and more in that file. For more information see here.

In Subnet-EVM, we provide a pre-configured file hardhat.config.ts.

The HardHat config file includes a single network configuration: local. local defaults to using the following values for the RPC URL and the Chain ID:

var local_rpc_uri = process.env.RPC_URI || "http://127.0.0.1:9650/ext/bc/C/rpc"
var local_chain_id = process.env.CHAIN_ID || 99999

You can use this network configuration by providing the environment variables and specifying the --network flag, as Subnet-EVM does in its testing suite:

RPC_URI=http://127.0.0.1:9650/ext/bc/28N1Tv5CZziQ3FKCaXmo8xtxoFtuoVA6NvZykAT5MtGjF4JkGs/rpc CHAIN_ID=77777 npx hardhat test --network local

Alternatively, you can copy and paste the local network configuration to create a new network configuration for your own local testing. For example, you can copy and paste the local network configuration to create your own network and fill in the required details:

{
  "networks": {
    "mynetwork": {
      "url": "http://127.0.0.1:9650/ext/bc/28N1Tv5CZziQ3FKCaXmo8xtxoFtuoVA6NvZykAT5MtGjF4JkGs/rpc",
      "chainId": 33333,
      "accounts": [
        "0x56289e99c94b6912bfc12adc093c9b51124f0dc54ac7a766b2bc5ccf558d8027",
        "0x7b4198529994b0dc604278c99d153cfd069d594753d471171a1d102a10438e07",
        "0x15614556be13730e9e8d6eacc1603143e7b96987429df8726384c2ec4502ef6e",
        "0x31b571bf6894a248831ff937bb49f7754509fe93bbd2517c9c73c4144c0e97dc",
        "0x6934bef917e01692b789da754a0eae31a8536eb465e7bff752ea291dad88c675",
        "0xe700bdbdbc279b808b1ec45f8c2370e4616d3a02c336e68d85d4668e08f53cff",
        "0xbbc2865b76ba28016bc2255c7504d000e046ae01934b04c694592a6276988630",
        "0xcdbfd34f687ced8c6968854f8a99ae47712c4f4183b78dcc4a903d1bfe8cbf60",
        "0x86f78c5416151fe3546dece84fda4b4b1e36089f2dbc48496faf3a950f16157c",
        "0x750839e9dbbd2a0910efe40f50b2f3b2f2f59f5580bb4b83bd8c1201cf9a010a"
      ],
      "pollingInterval": "1s"
    }
  }
}

By creating your own network configuration in the HardHat config, you can run HardHat commands directly on your subnet:

npx hardhat accounts --network mynetwork

Hardhat Tasks

You can define custom hardhat tasks in tasks.ts. Tasks contain helpers for precompiles allowList and minter. Precompiles have their own contract already-deployed when they're activated. So these can be called without deploying any intermediate contract. See npx hardhat --help for more information about available tasks.

Tests

Tests are written for a local network which runs a Subnet-EVM Blockchain.

E.g RPC_URI=http://127.0.0.1:9650/ext/bc/28N1Tv5CZziQ3FKCaXmo8xtxoFtuoVA6NvZykAT5MtGjF4JkGs/rpc CHAIN_ID=77777 npx hardhat test --network local.

Subnet-EVM must activate any precompiles used in the test in the genesis:

{
  "config": {
    "chainId": 43214,
    "homesteadBlock": 0,
    "eip150Block": 0,
    "eip150Hash": "0x2086799aeebeae135c246c65021c82b4e15a2c451340993aacfd2751886514f0",
    "eip155Block": 0,
    "eip158Block": 0,
    "byzantiumBlock": 0,
    "constantinopleBlock": 0,
    "petersburgBlock": 0,
    "istanbulBlock": 0,
    "muirGlacierBlock": 0,
    "subnetEVMTimestamp": 0,
    "feeConfig": {
      "gasLimit": 8000000,
      "minBaseFee": 25000000000,
      "targetGas": 15000000,
      "baseFeeChangeDenominator": 36,
      "minBlockGasCost": 0,
      "maxBlockGasCost": 1000000,
      "targetBlockRate": 2,
      "blockGasCostStep": 200000
    },
    "contractDeployerAllowListConfig": {
      "blockTimestamp": 0,
      "adminAddresses": ["0x8db97C7cEcE249c2b98bDC0226Cc4C2A57BF52FC"]
    },
    "contractNativeMinterConfig": {
      "blockTimestamp": 0,
      "adminAddresses": ["0x8db97C7cEcE249c2b98bDC0226Cc4C2A57BF52FC"]
    },
    "allowFeeRecipients": false
  },
  "alloc": {
    "8db97C7cEcE249c2b98bDC0226Cc4C2A57BF52FC": {
      "balance": "0x295BE96E64066972000000"
    }
  },
  "nonce": "0x0",
  "timestamp": "0x0",
  "extraData": "0x00",
  "gasLimit": "0x7A1200",
  "difficulty": "0x0",
  "mixHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "coinbase": "0x0000000000000000000000000000000000000000",
  "number": "0x0",
  "gasUsed": "0x0",
  "parentHash": "0x0000000000000000000000000000000000000000000000000000000000000000"
}