fix: prevent unhandled errors from superseded cart mutations

.changeset/quiet-cart-aborts.md

@@ -0,0 +1,5 @@
+---
+"@shopify/hydrogen": patch
+---
+
+Prevent superseded cart mutations from producing unhandled `AbortError` console errors.

packages/hydrogen/src/core/cart/cart-transactions.test.ts

@@ -407,6 +407,25 @@ describe("transaction cart store", () => {
     expect(store.getState().pending.lines).toEqual(new Set());
   });
 
+  it("handles an aborted correlated Standard Event promise", async () => {
+    dispatchEventsSynchronously = false;
+    store.hydrate(makeCart([makeLine("line-a", 1)]));
+    getCart.mockResolvedValueOnce({ cart: makeCart([makeLine("line-a", 3)]) });
+
+    const first = store.handleFormSubmit(submitLine("line-a"));
+    await Promise.resolve();
+    await Promise.resolve();
+    const second = store.handleFormSubmit(submitLine("line-a"));
+    await Promise.resolve();
+    await Promise.resolve();
+
+    expect(transportSignals[0].aborted).toBe(true);
+    transportDeferreds[1].resolve(serverResult([makeLine("line-a", 3)]));
+    await Promise.all([first, second]);
+
+    expect(store.getState().data.lines.nodes[0].quantity).toBe(3);
+  });
+
   it("retains references outside a transaction's scope", () => {
     const lineA = makeLine("line-a", 1);
     const lineB = makeLine("line-b", 1);

packages/hydrogen/src/core/cart/cart.ts

@@ -1533,6 +1533,8 @@ function enqueueTransaction<TType extends TransactionType>(
   );
   if (expectedEventIndex !== -1) {
     store.expectedEvents.splice(expectedEventIndex, 1);
+    // Prevent request cancellation from becoming an unhandled rejection.
+    promise.then(NOOP, NOOP);
     return;
   }
   if (store.observedPromises.has(promise)) return;