fix(catalog): alteração de preço não chega ao carrinho

services/catalog/catalog_service/app.py

@@ -88,15 +88,17 @@ async def get_product(product_id: str) -> dict:
 
     @app.patch("/products/{product_id}")
     async def update_product(product_id: str, body: ProductUpdate) -> dict:
-        product = db.update_product(product_id, body.name, body.price_cents, body.stock)
-        if product is None:
+        previous = db.get_product(product_id)
+        if previous is None:
             raise HTTPException(status_code=404, detail="produto não encontrado")
-        if body.price_cents is not None and body.price_cents != product["price_cents"]:
+        old_price_cents = previous["price_cents"]
+        product = db.update_product(product_id, body.name, body.price_cents, body.stock)
+        if body.price_cents is not None and body.price_cents != old_price_cents:
             await bus.publish(
                 new_event(
                     ProductPriceChanged(
                         product_id=product_id,
-                        old_price_cents=product["price_cents"],
+                        old_price_cents=old_price_cents,
                         new_price_cents=body.price_cents,
                     ),
                     PRODUCER,

services/catalog/tests/test_catalog.py

@@ -11,3 +11,36 @@ def test_create_product_publishes_event():
 
     assert response.status_code == 201
     assert [event.event_type for event in bus.published] == ["product.created"]
+
+
+def test_patch_price_publishes_price_changed_with_old_and_new_price():
+    """CAT-BUG-01 (RN-02): alterar o preço pelo PATCH deve publicar
+    product.price_changed, para que o carrinho atualize seu snapshot.
+    Sem a correção, o preço antigo era lido após o update e o evento
+    nunca era publicado (antigo == novo)."""
+    bus = InMemoryBus()
+    with TestClient(create_app(":memory:", bus)) as client:
+        created = client.post("/products", json={"name": "Mouse", "price_cents": 5000, "stock": 3}).json()
+        response = client.patch(f"/products/{created['id']}", json={"price_cents": 7500})
+
+        assert response.status_code == 200
+        assert client.get(f"/products/{created['id']}").json()["price_cents"] == 7500
+
+    changed = [event for event in bus.published if event.event_type == "product.price_changed"]
+    assert len(changed) == 1
+    assert changed[0].payload == {
+        "product_id": created["id"],
+        "old_price_cents": 5000,
+        "new_price_cents": 7500,
+    }
+
+
+def test_patch_without_price_change_does_not_publish_price_changed():
+    """Complemento CAT-BUG-01: PATCH que não muda o preço não gera evento."""
+    bus = InMemoryBus()
+    with TestClient(create_app(":memory:", bus)) as client:
+        created = client.post("/products", json={"name": "Mouse", "price_cents": 5000, "stock": 3}).json()
+        client.patch(f"/products/{created['id']}", json={"name": "Mouse Gamer"})
+        client.patch(f"/products/{created['id']}", json={"price_cents": 5000})
+
+    assert [event.event_type for event in bus.published] == ["product.created"]