feat: add pre and post receive message callbacks (#426)

* feat: add pre and post receive message callbacks

* fix: formatting

src/consumer.ts

@@ -38,6 +38,8 @@ export class Consumer extends TypedEventEmitter {
   private queueUrl: string;
   private handleMessage: (message: Message) => Promise<Message | void>;
   private handleMessageBatch: (message: Message[]) => Promise<Message[] | void>;
+  private preReceiveMessageCallback?: () => Promise<void>;
+  private postReceiveMessageCallback?: () => Promise<void>;
   private sqs: SQSClient;
   private handleMessageTimeout: number;
   private attributeNames: string[];
@@ -57,6 +59,8 @@ export class Consumer extends TypedEventEmitter {
     this.queueUrl = options.queueUrl;
     this.handleMessage = options.handleMessage;
     this.handleMessageBatch = options.handleMessageBatch;
+    this.preReceiveMessageCallback = options.preReceiveMessageCallback;
+    this.postReceiveMessageCallback = options.postReceiveMessageCallback;
     this.handleMessageTimeout = options.handleMessageTimeout;
     this.attributeNames = options.attributeNames || [];
     this.messageAttributeNames = options.messageAttributeNames || [];
@@ -223,10 +227,18 @@ export class Consumer extends TypedEventEmitter {
     params: ReceiveMessageCommandInput
   ): Promise<ReceiveMessageCommandOutput> {
     try {
-      return await this.sqs.send(
+      if (this.preReceiveMessageCallback) {
+        await this.preReceiveMessageCallback();
+      }
+      const result = await this.sqs.send(
         new ReceiveMessageCommand(params),
         this.sqsSendOptions
       );
+      if (this.postReceiveMessageCallback) {
+        await this.postReceiveMessageCallback();
+      }
+
+      return result;
     } catch (err) {
       throw toSQSError(err, `SQS receive message failed: ${err.message}`);
     }

src/types.ts

@@ -103,6 +103,22 @@ export interface ConsumerOptions {
    * the successful messages only.
    */
   handleMessageBatch?(messages: Message[]): Promise<Message[] | void>;
+  /**
+   * An `async` function (or function that returns a `Promise`) to be called right
+   * before the SQS Client sends a receive message command.
+   *
+   * This function is usefull if SQS Client module exports have been modified, for
+   * example to add middlewares.
+   */
+  preReceiveMessageCallback?(): Promise<void>;
+  /**
+   * An `async` function (or function that returns a `Promise`) to be called right
+   * after the SQS Client sends a receive message command.
+   *
+   * This function is usefull if SQS Client module exports have been modified, for
+   * example to add middlewares.
+   */
+  postReceiveMessageCallback?(): Promise<void>;
 }
 
 export type UpdatableOptions =

test/tests/consumer.test.ts

@@ -479,6 +479,30 @@ describe('Consumer', () => {
       sandbox.assert.calledWith(handleMessage, response.Messages[0]);
     });
 
+    it('calls the preReceiveMessageCallback and postReceiveMessageCallback function before receiving a message', async () => {
+      let callbackCalls = 0;
+
+      consumer = new Consumer({
+        queueUrl: QUEUE_URL,
+        region: REGION,
+        handleMessage,
+        sqs,
+        authenticationErrorTimeout: AUTHENTICATION_ERROR_TIMEOUT,
+        preReceiveMessageCallback: async () => {
+          callbackCalls++;
+        },
+        postReceiveMessageCallback: async () => {
+          callbackCalls++;
+        }
+      });
+
+      consumer.start();
+      await pEvent(consumer, 'message_processed');
+      consumer.stop();
+
+      assert.equal(callbackCalls, 2);
+    });
+
     it('deletes the message when the handleMessage function is called', async () => {
       handleMessage.resolves();