Cairo Setup

Project Scaffolding

Install toolchain and create a project:

curl --proto '=https' --tlsv1.2 -sSf https://sh.starkup.sh | sh
scarb new my_project --test-runner=starknet-foundry

This scaffolds a complete Starknet project with snforge testing preconfigured.

OpenZeppelin Dependencies

Look up the current version from https://docs.openzeppelin.com/contracts-cairo before adding. Add to Scarb.toml:

Full library (umbrella package):

[dependencies]
openzeppelin = "<VERSION>"

Individual packages (faster builds — only compiles what you use):

[dependencies]
openzeppelin_token = "<VERSION>"
openzeppelin_access = "<VERSION>"

Available individual packages: openzeppelin_access, openzeppelin_account, openzeppelin_finance, openzeppelin_governance, openzeppelin_interfaces, openzeppelin_introspection, openzeppelin_merkle_tree, openzeppelin_presets, openzeppelin_security, openzeppelin_token, openzeppelin_upgrades, openzeppelin_utils.

openzeppelin_interfaces and openzeppelin_utils are versioned independently. Check the docs for their specific versions. All other packages share the same version.

Import Conventions

The import path depends on which dependency is declared:

• Umbrella package (openzeppelin = "..."): use openzeppelin:: as the root
• Individual packages (openzeppelin_token = "..."): use the package name as the root

// Individual packages
use openzeppelin_token::erc20::{ERC20Component, ERC20HooksEmptyImpl};
use openzeppelin_access::ownable::OwnableComponent;
use openzeppelin_upgrades::UpgradeableComponent;

// Umbrella package equivalents
use openzeppelin::token::erc20::{ERC20Component, ERC20HooksEmptyImpl};
use openzeppelin::access::ownable::OwnableComponent;
use openzeppelin::upgrades::UpgradeableComponent;

Components are integrated via the component! macro, embedded impls, and substorage:

component!(path: ERC20Component, storage: erc20, event: ERC20Event);

#[abi(embed_v0)]
impl ERC20MixinImpl = ERC20Component::ERC20MixinImpl<ContractState>;
impl ERC20InternalImpl = ERC20Component::InternalImpl<ContractState>;

Storage collision warning: When composing multiple components, #[substorage(v0)] flattens component storage into the contract's namespace. If two components use the same internal storage variable names, they will silently share the same storage slot, causing state corruption. Review the source of each component you compose to verify there are no naming conflicts across components.