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`](../../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 ```solidity // 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) ```solidity 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 ```solidity 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+) ```solidity 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`](../../languages/solidity/developer.md) - Idioms: [`languages/solidity/idioms.md`](../../languages/solidity/idioms.md) - Gotchas: [`languages/solidity/gotchas.md`](../../languages/solidity/gotchas.md) - Sister roles: `chainsafe-solidity-architect`, `chainsafe-solidity-reviewer` (HARD FAIL tier)