Chainsafe Solidity Developer

Solidity Developer

Idiomatic Solidity at ChainSafe. Reviewer is HARD FAIL tier; this skill teaches you to stay out of HARD-FAIL territory. Full reference: languages/solidity/developer.md.

Tooling baselines

• Foundry preferred for new projects. forge, cast, anvil.
• Hardhat in entrenched projects.
• Pin pragma: pragma solidity 0.8.24; (not floating ^0.8.0).
• OpenZeppelin Contracts for ERC-20, ERC-721, AccessControl, ReentrancyGuard, Pausable.
• Solady / Solmate when gas matters and audit capacity backs gas-tuned code.
• slither as a CI baseline. Specific findings muted with // slither-disable-next-line ... reason: ... comments.
• mythril for symbolic execution on critical contracts.
• solhint for style.

Imports

// SPDX-License-Identifier: Apache-2.0
pragma solidity 0.8.24;

import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import {SafeERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import {ReentrancyGuard} from "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import {AccessControl} from "@openzeppelin/contracts/access/AccessControl.sol";

• Named imports over wildcard import "...".
• SPDX identifier at top of every file.

Checks-Effects-Interactions (the canonical pattern)

function withdraw(uint256 amount) external nonReentrant {
    // Checks
    if (amount == 0) revert ZeroAmount();
    if (balances[msg.sender] < amount) revert Insufficient(amount, balances[msg.sender]);

    // Effects
    balances[msg.sender] -= amount;
    totalDeposits -= amount;

    // Interactions
    (bool ok, ) = msg.sender.call{value: amount}("");
    if (!ok) revert TransferFailed();
}

Always in this order. nonReentrant on every external function calling untrusted code.

Access control

contract Vault is AccessControl, ReentrancyGuard {
    bytes32 public constant ADMIN_ROLE = keccak256("ADMIN");

    function setFee(uint256 newFee) external onlyRole(ADMIN_ROLE) { /* ... */ }
}

• AccessControl over Ownable for multi-action contracts.
• Lock down DEFAULT_ADMIN_ROLE.
• Multi-sig (Gnosis Safe) holds privileged roles in production. EOA only in dev/test.
• Timelocks on parameter changes.

Custom errors (0.8.4+)

error Insufficient(uint256 requested, uint256 available);

function withdraw(uint256 amount) external {
    if (balances[msg.sender] < amount) revert Insufficient(amount, balances[msg.sender]);
}

Smaller bytecode than require strings; structured data for callers.

External calls

• .call{value: amount}("") over .transfer / .send (which break with new gas pricing).
• Check return values. Unchecked = silent bugs.
• Use OpenZeppelin's SafeERC20.safeTransfer / safeTransferFrom — normalizes broken ERC-20s like USDT.

Function visibility

• external default for callable-from-outside (saves gas vs public for calldata args).
• public only when also called internally.
• internal for cross-contract-inheritance helpers.
• private rarely.

State variables

• Pack storage — group same-size types to share slots.
• immutable for constructor-set values.
• constant for compile-time-known values.
• Document storage layout for upgradeable contracts; __gap reserves slots.

Testing (Foundry)

• Unit tests in test/*.t.sol.
• Fuzz tests by parameterizing function arguments.
• Invariant tests declare properties that must always hold; forge finds breaking sequences.
• Differential tests against a reference implementation.
• Mainnet fork tests for integrations with deployed contracts.

Coverage via forge coverage. Security-critical code: 100% line coverage is necessary, not sufficient. Add fuzz + invariant tests.

CI baseline

• forge build
• forge test -vvv
• forge coverage with threshold (typically 95%+ for security-critical)
• slither .
• solhint 'src/**/*.sol'
• Mainnet fork tests on schedule
• Gas snapshot via forge snapshot --check to catch regressions

Anti-patterns (most are HARD FAIL findings)

• tx.origin for authorization.
• Floating pragma.
• Unbounded loops over user-controlled data.
• State changes after external calls.
• .transfer / .send for ETH.
• Custom math reimplementing audited primitives.
• assembly without justification.
• Owner-key control of production contracts.

Related

• Full reference: languages/solidity/developer.md
• Idioms: languages/solidity/idioms.md
• Gotchas: languages/solidity/gotchas.md
• Sister roles: chainsafe-solidity-architect, chainsafe-solidity-reviewer (HARD FAIL tier)