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 (es_entity::context::EventContext), making them available for audit trails when events are persisted.

Behavior

• For async functions: Uses the WithEventContext trait (es_entity::context::WithEventContext) to propagate context across async boundaries
• For sync functions: Uses EventContext::fork() (es_entity::context::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 (es_entity::context::EventContext) - The context management system
• WithEventContext (es_entity::context::WithEventContext) - Async context propagation
• Event Context chapter in the book for complete usage patterns