Agent skill

dojo-review

Review Dojo code for best practices, common mistakes, security issues, and optimization opportunities. Use when auditing models, systems, tests, or preparing for deployment.

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Install this agent skill to your Project

npx add-skill https://github.com/dojoengine/book/tree/main/skills/dojo-review

SKILL.md

Dojo Code Review

Review your Dojo code for common issues, security concerns, and optimization opportunities.

When to Use This Skill

  • "Review my Dojo code"
  • "Check this system for issues"
  • "Audit my models"
  • "Review before deploying"

What This Skill Does

Analyzes your code for:

  • Model design patterns
  • System implementation issues
  • Security vulnerabilities
  • Gas optimization opportunities
  • Test coverage gaps
  • Common mistakes

Quick Start

Interactive mode:

"Review my Dojo project"

I'll ask about:

  • What to review (models, systems, tests, all)
  • Focus areas (security, performance)

Direct mode:

"Review the combat system for security issues"
"Check if my models follow ECS patterns"

Review Categories

Model Review

Checks:

  • Required trait derivations (Drop, Serde)
  • Key fields defined correctly (#[key])
  • Keys come before data fields
  • Appropriate field types
  • Small, focused models (ECS principle)

Common issues:

cairo
// ❌ Missing required traits
#[dojo::model]
struct Position { ... }

// ✅ Required traits
#[derive(Drop, Serde)]
#[dojo::model]
struct Position { ... }

// ❌ Keys after data fields
struct Example {
    data: u32,
    #[key]
    id: u32,  // Must come first!
}

// ✅ Keys first
struct Example {
    #[key]
    id: u32,
    data: u32,
}

System Review

Checks:

  • Proper interface definition (#[starknet::interface])
  • Contract attribute (#[dojo::contract])
  • World access with namespace (self.world(@"namespace"))
  • Input validation
  • Event emissions
  • Error messages

Common issues:

cairo
// ❌ No input validation
fn set_health(ref self: ContractState, health: u8) {
    // Could be zero or invalid!
}

// ✅ Input validation
fn set_health(ref self: ContractState, health: u8) {
    assert(health > 0 && health <= 100, 'invalid health');
}

// ❌ No authorization check for sensitive function
fn admin_function(ref self: ContractState) {
    // Anyone can call!
}

// ✅ Authorization check
fn admin_function(ref self: ContractState) {
    let mut world = self.world_default();
    let caller = get_caller_address();
    assert(
        world.is_owner(selector_from_tag!("my_game"), caller),
        'not authorized'
    );
}

Security Review

Checks:

  • Authorization on sensitive functions
  • Integer overflow/underflow
  • Access control for model writes
  • State consistency

Common vulnerabilities:

cairo
// ❌ Integer underflow
health.current -= damage;  // Could underflow if damage > current!

// ✅ Safe subtraction
health.current = if health.current > damage {
    health.current - damage
} else {
    0
};

// ❌ Missing ownership check
fn transfer_nft(ref self: ContractState, token_id: u256, to: ContractAddress) {
    // Anyone can transfer anyone's NFT!
    let mut nft: NFT = world.read_model(token_id);
    nft.owner = to;
    world.write_model(@nft);
}

// ✅ Ownership check
fn transfer_nft(ref self: ContractState, token_id: u256, to: ContractAddress) {
    let mut world = self.world_default();
    let caller = get_caller_address();

    let mut nft: NFT = world.read_model(token_id);
    assert(nft.owner == caller, 'not owner');

    nft.owner = to;
    world.write_model(@nft);
}

Gas Optimization

Checks:

  • Minimal model reads/writes
  • Efficient data types
  • Unnecessary computations

Optimization opportunities:

cairo
// ❌ Multiple reads of same model
let pos: Position = world.read_model(player);
let x = pos.x;
let pos2: Position = world.read_model(player);  // Duplicate!
let y = pos2.y;

// ✅ Single read
let pos: Position = world.read_model(player);
let x = pos.x;
let y = pos.y;

// ❌ Oversized types
struct Position {
    #[key]
    player: ContractAddress,
    x: u128,  // Overkill for coordinates
    y: u128,
}

// ✅ Appropriate types
struct Position {
    #[key]
    player: ContractAddress,
    x: u32,  // Sufficient for most games
    y: u32,
}

Test Coverage

Checks:

  • Unit tests for models
  • Integration tests for systems
  • Edge case coverage
  • Failure case testing

Coverage gaps:

cairo
// Missing tests:
// - Boundary values (max health, zero health)
// - Unauthorized access
// - Invalid inputs
// - Full workflow integration

// Add:
#[test]
fn test_health_bounds() { ... }

#[test]
#[should_panic(expected: ('not authorized',))]
fn test_unauthorized_access() { ... }

#[test]
fn test_spawn_move_attack_flow() { ... }

Review Checklist

Models

  • All models derive Drop and Serde
  • Key fields have #[key] attribute
  • Keys come before data fields
  • Models are small and focused
  • Field types are appropriate size
  • Custom types derive Introspect

Systems

  • Interface uses #[starknet::interface]
  • Contract uses #[dojo::contract]
  • World access uses correct namespace
  • Input validation for all parameters
  • Clear error messages
  • Events emitted for important actions
  • Caller identity verified when needed

Security

  • Sensitive functions check permissions
  • Integer math handles over/underflow
  • Ownership verified before transfers
  • State changes are atomic

Performance

  • Minimal model reads per function
  • Efficient data types used
  • No unnecessary computations

Tests

  • Unit tests for models
  • Integration tests for systems
  • Edge cases tested
  • Failure cases tested with #[should_panic]

Common Anti-Patterns

God Models

cairo
// ❌ Everything in one model
#[dojo::model]
struct Player {
    #[key] player: ContractAddress,
    x: u32, y: u32,  // Position
    health: u8, mana: u8,  // Stats
    gold: u32, items: u8,  // Inventory
    level: u8, xp: u32,  // Progress
}

// ✅ Separate concerns (ECS pattern)
Position { player, x, y }
Stats { player, health, mana }
Inventory { player, gold, items }
Progress { player, level, xp }

Missing world_default Helper

cairo
// ❌ Repeating namespace everywhere
fn spawn(ref self: ContractState) {
    let mut world = self.world(@"my_game");
    // ...
}

fn move(ref self: ContractState, direction: u8) {
    let mut world = self.world(@"my_game");
    // ...
}

// ✅ Use internal helper
#[generate_trait]
impl InternalImpl of InternalTrait {
    fn world_default(self: @ContractState) -> dojo::world::WorldStorage {
        self.world(@"my_game")
    }
}

fn spawn(ref self: ContractState) {
    let mut world = self.world_default();
    // ...
}

Not Emitting Events

cairo
// ❌ No events
fn transfer(ref self: ContractState, to: ContractAddress, amount: u256) {
    // Transfer logic but no event
}

// ✅ Emit events for indexing
fn transfer(ref self: ContractState, to: ContractAddress, amount: u256) {
    // Transfer logic
    world.emit_event(@Transferred { from, to, amount });
}

Next Steps

After code review:

  1. Fix identified issues
  2. Add missing tests
  3. Re-run review to verify fixes
  4. Use dojo-test skill to ensure tests pass
  5. Use dojo-deploy skill when ready

Related Skills

  • dojo-model: Fix model issues
  • dojo-system: Fix system issues
  • dojo-test: Add missing tests
  • dojo-deploy: Deploy after review

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