Discussion/doc cart's behaviour

[Platonn]

There are many nuances in the cart's mechanism. It would be good to document all those. Then we can think of optimizing current architecture of OCC API and Sparatacus code. We should also cover all those documented nuances with e2e tests.

For example:

• cart of anonymous user is merged into exiting user's cart after login
• for calls to OCC we use userId 'anonymous' for unsigned users and real userId for signed ones
• for calls to OCC we use cartId 'current' (or cart.code? I'm not sure) for signed users and cart.guid for unsigned users
• we shouldn't load cart from backend when it's not created (question: it may be OK for unsigned users, but for signed may lead to two active carts on different devices, see https://github.com/SAP/cloud-commerce-spartacus-storefront/issues/3592)
• we should re-load cart from backend after all actions, i.e. like add cart entry (question: can we optimize backend API to return cart as a result of adding cart entry?)
• when cart doesn't exist in backend, we should create it just before user adds the first item to the cart
• question: can/should a signed user have different carts on different devices? (I guess not)

It's an open discussion. So please share thoughts in comments.

[WeizhengSap]

1. When user login:

1.1. If there is no anonymous cart, we just load user's current cart. (In OCC, there is no 'load current cart' API, so we load all user's carts, and return the first one. )

• If user doesn't have carts at all (new register user), then no cart received from backend.
• If user has carts, we get the latest one. (current cart)

1.2. If there is anonymous cart, then we load user's current cart and do the merge.

• If user doen't have carts at all, the anonymous cart becomes user's active cart.

• If user has current cart, we merge the anonymous cart into the current cart.

• for calls to OCC we use userId 'anonymous' for unsigned users and real userId for signed ones
• when getting user cart without cartId, then we use current (e.g. we don't know the cartId when user login) . If there is cartId, we use cartId.
• for login user, cartId is cart's code; for anonymous user, cartId is guid
• we shouldn't load cart from backend when it's not created (question: it may be OK for unsigned users, but for signed may lead to two active carts on different devices, see SAP/cloud-commerce-spartacus-storefront#3592) How do you load cart? by cartId or by current? If by cartId, then cart must exist in backend; if by current, it doesn't matter cart exist or not. If not exist, you just get empty value.
• we should re-load cart from backend after all actions, i.e. like add cart entry (Now, OCC returns CartModification data)
• when cart doesn't exist in backend, we should create it just before user adds the first item to the cart
• question: can/should a signed user have different carts on different devices (no, always the first unsaved cart in the user's carts list)

[plabadie]

About 'current' vs 'anonymous':

For occ calls in general in Spartacus, when a userId is required in the occ call url, the app uses the special id 'current', which tells the server to obtain the userId from the auth token provided in the request.

When no user is authenticated, the user id 'anonymous' is used in the url of occ calls that require a userId in the url.