Hardhat Best Practices and Coding Standards
hardhatethereumsmart-contractssoliditydapps
Description
This rule outlines best practices for Hardhat development, covering code organization, security, testing, and performance. It aims to provide a comprehensive guide for developers working with the Hardhat Ethereum development environment.
Globs
**/*.{js,ts,sol,json}---
description: This rule outlines best practices for Hardhat development, covering code organization, security, testing, and performance. It aims to provide a comprehensive guide for developers working with the Hardhat Ethereum development environment.
globs: **/*.{js,ts,sol,json}
---
# Hardhat Best Practices and Coding Standards
This document provides a comprehensive guide to best practices for developing smart contracts and decentralized applications (dApps) using Hardhat. It covers code organization, security, testing, performance, and other essential aspects of Hardhat development.
## 1. Code Organization and Structure
### 1.1. Directory Structure Best Practices
hardhat-project/
├── contracts/ # Solidity smart contracts
│ ├── MyContract.sol
│ └── ...
├── scripts/ # Deployment and interaction scripts
│ ├── deploy.js
│ ├── interact.js
│ └── ...
├── test/ # Unit and integration tests
│ ├── MyContract.test.js
│ └── ...
├── hardhat.config.js # Hardhat configuration file
├── package.json # Node.js package file
├── README.md # Project documentation
└── .gitignore # Git ignore file
- **contracts/:** Store all Solidity smart contracts in this directory. Consider subdirectories for different modules or features.
- **scripts/:** Keep deployment, interaction, and other utility scripts in this directory. Organize scripts by function or deployment environment.
- **test/:** Place all unit and integration tests in this directory. Mirror the `contracts/` directory structure for test files.
- **hardhat.config.js:** Configure Hardhat settings in this file, including compiler versions, network configurations, and task definitions. Consider using TypeScript.
- **package.json:** Manage project dependencies and scripts using npm or yarn.
- **README.md:** Provide clear and concise documentation for your project.
- **.gitignore:** Exclude unnecessary files from source control (e.g., build artifacts, node_modules).
### 1.2. File Naming Conventions
- **Solidity Files:** Use PascalCase with the `.sol` extension for Solidity contract files (e.g., `MyContract.sol`).
- **JavaScript/TypeScript Files:** Use camelCase with the `.js` or `.ts` extension for JavaScript/TypeScript files (e.g., `deploy.js`, `myContract.test.ts`).
- **Test Files:** Use the `.test.js` or `.test.ts` suffix to identify test files (e.g., `MyContract.test.js`).
### 1.3. Module Organization
- **Separate Concerns:** Divide your contracts into logical modules or components based on their functionality.
- **Interfaces:** Use interfaces to define the public API of your contracts.
- **Libraries:** Create reusable libraries for common functionalities to avoid code duplication.
- **Abstract Contracts:** Use abstract contracts to define common logic and state variables for related contracts.
### 1.4. Component Architecture
- **Modular Design:** Design contracts as independent, reusable components.
- **Composition:** Combine smaller components to create more complex systems.
- **Minimal Dependencies:** Reduce dependencies between components to improve maintainability and testability.
### 1.5. Code Splitting Strategies
- **Separate Logic and Data:** Keep contract logic separate from data storage to improve readability and maintainability.
- **External Libraries:** Utilize external libraries (e.g., OpenZeppelin) for common functionalities to reduce code size and improve security.
- **Proxy Patterns:** Consider using proxy patterns to enable upgradeability and code splitting.
## 2. Common Patterns and Anti-patterns
### 2.1. Design Patterns Specific to Hardhat/Solidity
- **Ownable:** Control access to privileged functions using the Ownable pattern (from OpenZeppelin).
- **Pausable:** Implement a Pausable contract to temporarily halt contract functionality in case of emergencies.
- **Pull over Push:** Favor pull-based payment mechanisms over push-based mechanisms to mitigate reentrancy attacks.
- **Proxy patterns (e.g., UUPS, Transparent Proxy):** For contract upgrades.
### 2.2. Recommended Approaches for Common Tasks
- **Deployment:** Use Hardhat's deployment scripts and network configurations to automate contract deployment.
- **Testing:** Employ Hardhat's testing framework and Chai matchers for comprehensive unit and integration testing.
- **Interaction:** Utilize Hardhat's console and Ethers.js for interacting with deployed contracts.
- **Verification:** Verify contract source code on Etherscan to enhance transparency and trust.
### 2.3. Anti-patterns and Code Smells to Avoid
- **Unchecked Arithmetic:** Use SafeMath or Solidity 0.8+ to prevent integer overflow/underflow.
- **Reentrancy:** Protect against reentrancy attacks by using the Checks-Effects-Interactions pattern or reentrancy guards (from OpenZeppelin).
- **Denial of Service (DoS):** Avoid patterns that can lead to DoS attacks, such as unbounded loops or expensive operations.
- **Timestamp Dependence:** Avoid relying on block timestamps for critical logic, as they can be manipulated by miners.
- **Insufficient Gas Limits:** Ensure functions have sufficient gas limits, especially for complex operations.
- **Hardcoding Addresses/Values:** Use configuration files or environment variables for addresses and other configurable values.
### 2.4. State Management Best Practices
- **Minimize State Variables:** Reduce the number of state variables to minimize storage costs and improve performance.
- **Use Appropriate Data Types:** Choose the most efficient data types for state variables (e.g., `uint256` instead of `uint`).
- **Immutability:** Use `immutable` variables when the value is assigned at construction and never changed after.
- **Constants:** Use `constant` variables for gas optimization when the value is known at compile time and never changed after.
- **Events:** Emit events to track state changes and enable off-chain monitoring.
### 2.5. Error Handling Patterns
- **Require Statements:** Use `require` statements to validate inputs and enforce preconditions.
- **Revert Statements:** Use `revert` statements to handle exceptional conditions and return informative error messages.
- **Custom Errors:** Use custom errors (Solidity 0.8.4+) for gas optimization and detailed error reporting.
- **Try/Catch (Solidity 0.8.16+):** Implement Try/Catch blocks when calling external contracts.
## 3. Performance Considerations
### 3.1. Optimization Techniques
- **Gas Optimization:** Minimize gas consumption to reduce transaction costs.
- **Data Packing:** Pack multiple small variables into a single storage slot to reduce storage costs.
- **Short Circuiting:** Use short-circuiting evaluation in logical expressions to avoid unnecessary computations.
- **Assembly Optimization:** Use inline assembly for performance-critical sections of code.
- **Caching:** Cache values that are frequently accessed.
### 3.2. Memory Management
- **Minimize Memory Usage:** Reduce memory usage to avoid out-of-gas errors.
- **Storage vs. Memory:** Use storage for persistent data and memory for temporary data.
- **Delete Unused Variables:** Delete variables in memory after use to free up space.
### 3.3. Rendering Optimization (If applicable - for frontend DApps)
- **Lazy Loading:** Load components and data only when they are needed.
- **Virtualization:** Use virtualization techniques to render large lists efficiently.
- **Memoization:** Memoize computationally expensive functions to avoid redundant calculations.
### 3.4. Bundle Size Optimization (If applicable - for frontend DApps)
- **Code Splitting:** Split the application code into smaller bundles to improve initial load time.
- **Tree Shaking:** Remove unused code from the bundle using tree shaking.
- **Minification:** Minify JavaScript and CSS files to reduce bundle size.
### 3.5. Lazy Loading Strategies (If applicable - for frontend DApps)
- **Dynamic Imports:** Use dynamic imports to load modules on demand.
- **Intersection Observer:** Use the Intersection Observer API to load resources when they become visible.
## 4. Security Best Practices
### 4.1. Common Vulnerabilities and How to Prevent Them
- **Reentrancy:** Use Checks-Effects-Interactions pattern. Employ reentrancy guards (@openzeppelin/contracts/security/ReentrancyGuard.sol).
- **Integer Overflow/Underflow:** Use SafeMath or Solidity 0.8+.
- **Denial of Service (DoS):** Limit gas costs, avoid unbounded loops, and implement rate limiting.
- **Timestamp Dependence:** Avoid relying on block timestamps for critical logic.
- **Front Running:** Design contracts to be resilient to front-running attacks.
- **Signature Replay:** Prevent signature replay attacks by using nonces or other unique identifiers.
- **Cross-Site Scripting (XSS):** Sanitize user inputs in frontend DApps to prevent XSS attacks.
- **SQL Injection:** Use parameterized queries to prevent SQL injection attacks in backend systems.
- **Improper Access Control:** Enforce strict access control policies to protect sensitive data and functions.
### 4.2. Input Validation
- **Sanitize Inputs:** Sanitize and validate all user inputs to prevent malicious data from entering the system.
- **Check Data Types:** Verify that inputs are of the expected data types.
- **Limit Input Length:** Restrict the length of input strings to prevent buffer overflows.
- **Regular Expressions:** Use regular expressions to validate complex input patterns.
### 4.3. Authentication and Authorization Patterns
- **Role-Based Access Control (RBAC):** Implement RBAC to manage user permissions.
- **Attribute-Based Access Control (ABAC):** Use ABAC for more fine-grained access control.
- **Multi-Factor Authentication (MFA):** Implement MFA to enhance security.
- **OAuth:** Use OAuth for secure delegation of access to third-party applications.
### 4.4. Data Protection Strategies
- **Encryption:** Encrypt sensitive data at rest and in transit.
- **Hashing:** Use hashing to store passwords securely.
- **Salting:** Salt passwords to prevent rainbow table attacks.
- **Key Management:** Implement secure key management practices.
### 4.5. Secure API Communication (If applicable - for backend systems)
- **HTTPS:** Use HTTPS for all API communication.
- **API Keys:** Use API keys to authenticate API requests.
- **Rate Limiting:** Implement rate limiting to prevent abuse.
- **Input Validation:** Validate and sanitize all API inputs.
## 5. Testing Approaches
### 5.1. Unit Testing Strategies
- **Test Driven Development (TDD):** Write tests before writing code.
- **Black Box Testing:** Test the functionality of the contract without knowledge of the internal implementation.
- **White Box Testing:** Test the internal implementation of the contract, including branches and loops.
- **Coverage Analysis:** Use coverage analysis tools to ensure that all code is covered by tests.
### 5.2. Integration Testing
- **Test Contract Interactions:** Test the interactions between multiple contracts.
- **Test External Dependencies:** Test the integration with external dependencies, such as oracles or other smart contracts.
### 5.3. End-to-End Testing (If applicable - for frontend DApps)
- **Simulate User Flows:** Simulate real-world user flows to test the entire application stack.
- **Automated Testing:** Use automated testing tools to run end-to-end tests regularly.
### 5.4. Test Organization
- **Arrange-Act-Assert:** Organize tests using the Arrange-Act-Assert pattern.
- **Descriptive Test Names:** Use descriptive names for tests to clearly indicate their purpose.
- **Test Suites:** Group related tests into test suites.
### 5.5. Mocking and Stubbing
- **Mock External Dependencies:** Use mocking to isolate contracts from external dependencies during testing.
- **Stub Function Calls:** Use stubbing to replace function calls with predefined values or behaviors.
## 6. Common Pitfalls and Gotchas
### 6.1. Frequent Mistakes Developers Make
- **Incorrectly handling gas costs**
- **Failing to validate inputs**
- **Ignoring security best practices**
- **Not writing enough tests**
- **Misunderstanding Ethereum's execution model**
- **Not using the latest compiler version**
### 6.2. Edge Cases to Be Aware Of
- **Integer overflow/underflow**
- **Reentrancy attacks**
- **Denial-of-service attacks**
- **Front-running attacks**
- **Signature replay attacks**
### 6.3. Version-Specific Issues
- **Solidity compiler bugs:** Be aware of known bugs in the Solidity compiler and use appropriate workarounds.
- **Hardhat version compatibility:** Ensure that Hardhat and its plugins are compatible with each other.
### 6.4. Compatibility Concerns
- **EVM version compatibility:** Consider the target EVM version when developing contracts.
- **Web3.js/Ethers.js compatibility:** Ensure compatibility with the chosen JavaScript library for interacting with the blockchain.
### 6.5. Debugging Strategies
- **Console.log:** Use `console.log` statements to debug code.
- **Hardhat console:** Use the Hardhat console for interactive debugging.
- **Truffle debugger:** Use the Truffle debugger for more advanced debugging.
- **Remix IDE:** Use Remix IDE for online debugging.
- **Solidity stack traces:** Use Solidity stack traces to identify the source of errors.
## 7. Tooling and Environment
### 7.1. Recommended Development Tools
- **Hardhat:** Ethereum development environment.
- **Visual Studio Code:** Code editor with Solidity support.
- **Remix IDE:** Online Solidity IDE.
- **Etherscan:** Blockchain explorer.
- **Ganache:** Local Ethereum blockchain.
- **OpenZeppelin:** Secure smart contract libraries.
### 7.2. Build Configuration
- **Hardhat configuration file:** Configure Hardhat settings in the `hardhat.config.js` file.
- **Compiler version:** Specify the Solidity compiler version in the Hardhat configuration file.
- **Optimization settings:** Configure optimization settings in the Hardhat configuration file.
### 7.3. Linting and Formatting
- **Solhint:** Solidity linter.
- **Prettier:** Code formatter.
- **ESLint:** JavaScript/TypeScript linter.
### 7.4. Deployment Best Practices
- **Automated deployments:** Use Hardhat's deployment scripts to automate contract deployment.
- **Network configurations:** Configure network settings in the Hardhat configuration file.
- **Gas price estimation:** Estimate gas prices before deploying contracts.
- **Contract verification:** Verify contract source code on Etherscan after deployment.
### 7.5. CI/CD Integration
- **Continuous integration:** Integrate Hardhat with CI/CD systems (e.g., GitHub Actions, Jenkins) to automate testing and deployment.