Attribute Macro es_event_context 

#[es_event_context]

Automatically captures function arguments into the event context.

This attribute macro wraps functions to automatically insert specified arguments into the current EventContext, making them available for audit trails when events are persisted.

Behavior

• For async functions: Uses the WithEventContext trait to propagate context across async boundaries
• For sync functions: Uses EventContext::fork() to create an isolated child context

Syntax

#[es_event_context]              // No arguments captured
#[es_event_context(arg1)]         // Capture single argument
#[es_event_context(arg1, arg2)]   // Capture multiple arguments

Examples

Async function with argument capture

use es_entity_macros::es_event_context;

impl UserService {
    #[es_event_context(user_id, operation)]
    async fn update_user(&self, user_id: UserId, operation: &str, data: UserData) -> Result<()> {
        // user_id and operation are automatically added to context
        // They will be included when events are persisted
        self.repo.update(data).await
    }
}

Sync function with context isolation

use es_entity_macros::es_event_context;

impl Calculator {
    #[es_event_context(transaction_id)]
    fn process(&mut self, transaction_id: u64, amount: i64) {
        // transaction_id is captured in an isolated context
        // Parent context is restored when function exits
        self.apply_transaction(amount);
    }
}

Manual context additions

use es_entity_macros::es_event_context;
use es_entity::context::EventContext;

#[es_event_context(request_id)]
async fn handle_request(request_id: String, data: RequestData) {
    // request_id is automatically captured
     
    // You can still manually add more context
    let mut ctx = EventContext::current();
    ctx.insert("timestamp", &chrono::Utc::now()).unwrap();
     
    process_data(data).await;
}

Context Keys

Arguments are captured using their parameter names as keys. For example, user_id: UserId will be stored with key "user_id" in the context.

See Also

• EventContext - The context management system
• WithEventContext - Async context propagation
• Event Context chapter in the book for complete usage patterns