Support discriminated unions for queue message batches #2795

cloudkite · 2024-09-24T22:16:58Z

When a worker is a consumer for multiple queues its not possible with the existing types to make the message body type depend on the name of the queue.

Changing the queue name to be generic would allow creating a discriminated union type for different message batches

- export interface MessageBatch<Body = unknown> {
+ export interface MessageBatch<Body = unknown, Name = string> {
   readonly messages: readonly Message<Body>[];
-  readonly queue: string;
+  readonly queue: Name;
   retryAll(options?: QueueRetryOptions): void;
   ackAll(): void;
 }

Which then enables:

type Batch = 
   | MessageBatch<{ foo: number }, "queue-1">
   | MessageBatch<{ bar: number }, "queue-2">

export default class extends WorkerEntrypoint {
  async queue(_batch: Batch) {
      switch (batch.queue) {
        case "queue-1": {
          // message.body is typed as { foo: number } here
          break;
        }
        case "queue-2": {
          // message.body is typed as { bar: number } here
          break;
        }
    }
  }
}

cloudkite added the types Related to @cloudflare/workers-types label Sep 24, 2024

cloudkite assigned workers-devprod Sep 24, 2024

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Support discriminated unions for queue message batches #2795

Support discriminated unions for queue message batches #2795

cloudkite commented Sep 24, 2024 •

edited

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Support discriminated unions for queue message batches #2795

Support discriminated unions for queue message batches #2795

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cloudkite commented Sep 24, 2024 • edited Loading

cloudkite commented Sep 24, 2024 •

edited

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