Struct EventEmitter 

pub struct EventEmitter<'a> {
    pub ctx: &'a RequestContext,
    pub queue: &'a (dyn EventQueueWriter + 'static),
}

Ergonomic helper for emitting status and artifact events from an executor.

Caches task_id and context_id from the RequestContext so that every event emission is a one-liner instead of a 7-line struct literal.

Example

use a2a_protocol_server::executor_helpers::EventEmitter;
use a2a_protocol_types::task::TaskState;
use a2a_protocol_types::message::Part;

let emit = EventEmitter::new(ctx, queue);
emit.status(TaskState::Working).await?;
emit.artifact("result", vec![Part::text("hello")], None, Some(true)).await?;
emit.status(TaskState::Completed).await?;

Fields

ctx: &'a RequestContext

The request context for this execution.

queue: &'a (dyn EventQueueWriter + 'static)

The event queue writer for this execution.

Implementations

impl<'a> EventEmitter<'a>

pub fn new( ctx: &'a RequestContext, queue: &'a (dyn EventQueueWriter + 'static), ) -> EventEmitter<'a>

Creates a new EventEmitter from the given context and queue.

pub async fn status(&self, state: TaskState) -> Result<(), A2aError>

Emits a status update event.

Errors

Returns an error if the event queue write fails.

pub async fn fail( &self, class: FailureClass, reason: impl Into<String>, ) -> Result<(), A2aError>

Emits the terminal Failed status, saying why in a form a caller can branch on.

An executor that returns Err instead gets a class inferred from the error code, which can only ever be InvalidRequest or Internal — no ErrorCode means “transient” or “refused on policy” — unless it recorded one on the error with set_error_class. An agent that knows it was rate limited upstream, or declined on a safety rule, is the only thing that can say so; this is one way, and the one that lets it keep writing its own status text.

// Retry me: the model was rate limited, not wrong.
emit.fail(FailureClass::Transient, "upstream model returned 429").await?;

Errors

Returns an error if the event queue write fails.

pub async fn artifact( &self, id: &str, parts: Vec<Part>, append: Option<bool>, last_chunk: Option<bool>, ) -> Result<(), A2aError>

Emits an artifact update event.

Errors

Returns an error if the event queue write fails.

pub fn is_cancelled(&self) -> bool

Returns true if the task has been cancelled.