Move cart composition from Python to .sx defcomps (Phase 5)

- render_orders_rows: Python loop building row-pairs → ~cart-orders-rows-content
  defcomp that maps over order data and handles pagination sentinel
- render_checkout_error_page: conditional order badge composition →
  ~cart-checkout-error-from-data defcomp
- Remove unused SxExpr import

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cart/sx/layouts.sx

@@ -116,3 +116,21 @@
 
 (defcomp ~cart-orders-rows (&key rows next-scroll)
   (<> rows next-scroll))
+
+;; Composition defcomp — replaces Python loop in render_orders_rows
+(defcomp ~cart-orders-rows-content (&key orders detail-url-prefix page total-pages next-url)
+  (~cart-orders-rows
+    :rows (map (lambda (od)
+      (~order-row-pair :order od :detail-url-prefix detail-url-prefix))
+      (or orders (list)))
+    :next-scroll (if (< page total-pages)
+      (~infinite-scroll :url next-url :page page
+        :total-pages total-pages :id-prefix "orders" :colspan 5)
+      (~order-end-row))))
+
+;; Composition defcomp — replaces conditional composition in render_checkout_error_page
+(defcomp ~cart-checkout-error-from-data (&key msg order-id back-url)
+  (~checkout-error-content
+    :msg msg
+    :order (when order-id (~checkout-error-order-id :oid (str "#" order-id)))
+    :back-url back-url))

cart/sxc/pages/renders.py

@@ -1,8 +1,6 @@
 """Cart render functions — called from bp routes."""
 from __future__ import annotations
 
-from shared.sx.parser import SxExpr
-
 from .utils import _serialize_order, _serialize_calendar_entry
 
 
@@ -32,20 +30,10 @@ def render_orders_rows(ctx, orders, page, total_pages, url_for_fn, qs_fn):
     list_url = pfx + url_for_fn("orders.list_orders")
     detail_url_prefix = pfx + url_for_fn("orders.order.order_detail", order_id=0).rsplit("0/", 1)[0]
     order_dicts = [_serialize_order(o) for o in orders]
-    parts = []
-    for od in order_dicts:
-        parts.append(sx_call("order-row-pair", order=od, detail_url_prefix=detail_url_prefix))
-    next_scroll = ""
-    if page < total_pages:
-        next_url = list_url + qs_fn(page=page + 1)
-        next_scroll = sx_call("infinite-scroll", url=next_url, page=page,
-            total_pages=total_pages, id_prefix="orders", colspan=5)
-    else:
-        next_scroll = sx_call("order-end-row")
-    return sx_call("cart-orders-rows",
-        rows=SxExpr("(<> " + " ".join(parts) + ")"),
-        next_scroll=next_scroll,
-    )
+    next_url = list_url + qs_fn(page=page + 1) if page < total_pages else ""
+    return sx_call("cart-orders-rows-content",
+        orders=order_dicts, detail_url_prefix=detail_url_prefix,
+        page=page, total_pages=total_pages, next_url=next_url)
 
 
 async def render_orders_oob(ctx, orders, page, total_pages, search, search_count, url_for_fn, qs_fn):
@@ -112,11 +100,11 @@ async def render_checkout_error_page(ctx, error=None, order=None):
     from shared.sx.helpers import sx_call, render_to_sx_with_env, full_page_sx
     from shared.infrastructure.urls import cart_url
     err_msg = error or "Unexpected error while creating the hosted checkout session."
-    order_sx = sx_call("checkout-error-order-id", oid=f"#{order.id}") if order else None
     hdr = await render_to_sx_with_env("layout-root-full", {})
     filt = sx_call("checkout-error-header")
-    content = sx_call("checkout-error-content", msg=err_msg,
-        order=order_sx or None, back_url=cart_url("/"))
+    content = sx_call("cart-checkout-error-from-data",
+        msg=err_msg, order_id=order.id if order else None,
+        back_url=cart_url("/"))
     return await full_page_sx(ctx, header_rows=hdr, filter=filt, content=content)