fix(pool): prevent race conditions in pool client return

Author: PavelPashov

packages/client/lib/client/pool.spec.ts

@@ -8,4 +8,35 @@ describe('RedisClientPool', () => {
       'PONG'
     );
   }, GLOBAL.SERVERS.OPEN);
+
+  testUtils.testWithClientPool(
+    'proper error propagation in sequential operations',
+    async (pool) => {
+      let hasUnhandledRejection = false;
+
+      process.once('unhandledRejection', () => {
+        hasUnhandledRejection = true;
+      });
+
+      const groupName = 'test-group';
+      const streamName = 'test-stream';
+
+      // First attempt - should succeed
+      await pool.xGroupCreate(streamName, groupName, '0', {
+        MKSTREAM: true,
+      });
+
+      // Subsequent attempts - should all throw BUSYGROUP errors and be handled properly
+      for (let i = 0; i < 3; i++) {
+        await assert.rejects(
+          pool.xGroupCreate(streamName, groupName, '0', {
+            MKSTREAM: true,
+          })
+        );
+      }
+
+      assert.equal(hasUnhandledRejection, false);
+    },
+    GLOBAL.SERVERS.OPEN
+  );
 });

packages/client/lib/client/pool.ts

@@ -438,8 +438,16 @@ export class RedisClientPool<
   ) {
     const result = fn(node.value);
     if (result instanceof Promise) {
-      result.then(resolve, reject);
-      result.finally(() => this.#returnClient(node))
+      result.then(
+        (value) => {
+          resolve(value);
+          this.#returnClient(node);
+        },
+        (error) => {
+          reject(error);
+          this.#returnClient(node);
+        }
+      );
     } else {
       resolve(result);
       this.#returnClient(node);