Accumulate state.include instead of replacing it

[acasazza]

state.include is the union of the resources every mounted component needs, but it was being replaced rather than accumulated — so components silently lost each other's includes.

Why this is worse than a missing field

Commerce Layer only embeds relationships you explicitly request, and the response cannot distinguish the two cases:

order.shipments[0].shipping_method === undefined  // "no method is selected"
order.shipments === undefined                     // "I didn't ask for shipments"

A dropped include therefore does not fail the request — it produces wrong application state. Losing shipments.shipping_method makes a selected shipping method look unselected.

Mechanism

setIncludesResource fell through to baseReducer, whose { ...state, ...payload } spread replaces include wholesale.

addResourceToInclude is a free function with no store access, so it can only union against the resourcesIncluded it is handed — and most of the 26 call sites don't pass it. Components that dispatch more than once from a single effect pass all read the same pre-update snapshot, so the last dispatch wins and the others' resources are gone.

PlaceOrderContainer does exactly this — three dispatches in one pass, only the third passing resourcesIncluded:

Block	Dispatches	Passes resourcesIncluded?
1	5 × shipments.* incl. shipments.shipping_method	no
2	billing_address	no
3	shipping_address	yes

The effect then re-runs, still sees shipments absent, and repeats the same self-defeating dance.

Confirmed on the wire

OrderReducer.includeRequest.spec.ts builds state through that exact dispatch sequence and asserts what getApiOrder passes to sdk.orders.retrieve. Against the old reducer:

AssertionError: expected [ 'line_items.item', …(1) ] to include 'shipments.shipping_method'

The request was include: ['line_items.item', 'shipping_address'] — shipments.shipping_method and billing_address genuinely absent. Not inferred from reading the code.

Fix

Handle the action in orderReducer and union there, so all 26 call sites are correct whether or not they pass resourcesIncluded. Fixing it here rather than in each caller is why this belongs in react-components instead of being worked around downstream.

Two behaviours are preserved deliberately:

• An explicitly empty list still resets — the effect teardown in useOrderState dispatches include: [] to clear the list, and a naive union would silently make that a no-op.
• include is left untouched when there is nothing to merge — callers that only report includeLoaded omit it, and turning undefined into [] would flip the include?.length === 0 checks in that same hook and change its effect dependencies.

Tests

Both new specs were verified to fail against the old reducer before being accepted (3 of 6, and 1 of 2), so they are regression tests rather than tautologies.

Notes

• Targets v5.0.0; main is the v4 line.
• Independent of Close payment-gateway render loop and repair gift-card/coupon submit #804 — verified on this base with the full suite green.
• pnpm typecheck reports 35 errors on this branch. They are byte-identical to the pre-existing baseline and unrelated to this change; clearing them is part of the separate dependency-upgrade work.

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