"Migrate my changes to the deployed world"

"Upgrade my project to Dojo v1.8.0"

sozo inspect

sozo build
sozo test

# Deploy with default dev profile
sozo migrate

# Deploy with specific profile
sozo migrate --profile sepolia

// New model - safe to add
#[derive(Copy, Drop, Serde)]
#[dojo::model]
pub struct NewFeature {
    #[key]
    pub player: ContractAddress,
    pub data: u32,
}

// New system - safe to add
#[dojo::contract]
pub mod new_system {
    // Implementation
}

// Adding field - existing data will have default (zero) value
struct Position {
    #[key] player: ContractAddress,
    x: u32,
    y: u32,
    z: u32,  // New field
}

// Old
struct Position {
    #[key] player: ContractAddress,
    x: u32, y: u32,
}

// New - BREAKING! Different key structure
struct Position {
    #[key] entity_id: u32,  // Changed key
    x: u32, y: u32,
}

// Old
struct Stats {
    #[key] player: ContractAddress,
    health: u8,
    mana: u8,
}

// New - BREAKING! Data loss
struct Stats {
    #[key] player: ContractAddress,
    health: u8,
    // mana removed
}

// Old
struct Position {
    #[key] player: ContractAddress,
    x: u32,
    y: u32,
}

// New - BREAKING! Type incompatible
struct Position {
    #[key] player: ContractAddress,
    x: u128,  // Changed type
    y: u128,
}

# dojo_dev.toml
[world]
seed = "my_game_v2"  # Different seed = new world address

sozo build && sozo migrate

// Keep old model
#[derive(Copy, Drop, Serde)]
#[dojo::model]
pub struct PositionV1 {
    #[key] player: ContractAddress,
    x: u32, y: u32,
}

// Add new model
#[derive(Copy, Drop, Serde)]
#[dojo::model]
pub struct PositionV2 {
    #[key] entity_id: u32,
    x: u32, y: u32, z: u32,
}

#[dojo::contract]
pub mod migrator {
    fn migrate_positions(ref self: ContractState, players: Array<ContractAddress>) {
        let mut world = self.world_default();

        for player in players {
            // Read old format
            let old_pos: PositionV1 = world.read_model(player);

            // Transform to new format
            let new_pos = PositionV2 {
                entity_id: world.uuid(),
                x: old_pos.x,
                y: old_pos.y,
                z: 0,
            };

            // Write new format
            world.write_model(@new_pos);
        }
    }
}

[dependencies]
dojo = "1.8.0"

[dev-dependencies]
dojo_cairo_test = "1.8.0"

sozo build
sozo test

sozo migrate

# 1. Add model to code
# 2. Build
sozo build

# 3. Migrate
sozo migrate

# 4. Verify
sozo inspect

# 1. Update system code
# 2. Build and test
sozo build
sozo test

# 3. Migrate (redeploys system)
sozo migrate

# 4. Test updated system
sozo execute my_game-actions spawn