[POS] Add s-pos-list and the posListTemplate compiler (2026-10)

[ajanth-u]

What

Adds <s-pos-list> for POS API version 2026-10 and the posListTemplate tagged template that compiles its row markup. This is the templated candidate for GSD #51755; the legacy-parity alternative is #4661 (unmodified, held as contingency). Exactly one of the two should merge.

Companion PRs: World #2061117 (ui-api-design contract), #2061112 → #2061124 → #2061132 (pos-mobile host stack), Shopify/pos-e2e-ui-extension (sandbox screen, follows), World shopify-dev docs (follows).

Design

rows is plain data ({id, templateFor, ...fields}) and itemTemplates is a compiled AST produced once in the extension bundle by posListTemplate:

const itemTemplates = posListTemplate`
  <s-pos-list-item templateId="section-header" type="text">
    <s-heading>{{title}}</s-heading>
  </s-pos-list-item>
  <s-pos-list-item templateId="product">
    <s-stack direction="inline">
      <s-image src="{{image.src}}" alt="{{name}}" />
      <s-text>{{name}}</s-text>
      {{#if onSale}}<s-badge tone="success">Sale</s-badge>{{/if}}
      <s-switch bind:checked="active" />
    </s-stack>
  </s-pos-list-item>
`;
<s-pos-list rows={rows} itemTemplates={itemTemplates} onRowClick={(e) => e.detail.item.id} />

POS hydrates one template copy per FlashList-mounted row, so no extension code runs while scrolling and no functions cross the bridge (no Shopify/extensibility change needed).

Grammar: {{path}} in text; {{path}} inside an attribute (always a string); bind:prop="path" (the only typed binding); {{#if path}}…{{/if}} (no nesting, no else). Rejected at compile time with posListTemplate:-prefixed errors: on* attributes, ${} interpolation of any kind, #each/other expressions, nested/unbalanced #if, #if inside an attribute, text directly under <s-pos-list-item>, non-item roots, nested s-pos-list-item/s-pos-list, missing/duplicate templateId, unknown type, any other root attribute.

Changes

• src/surfaces/point-of-sale/pos-list-template.ts — the compiler (htm-based; htm becomes a direct dependency).
• src/surfaces/point-of-sale.ts — exports posListTemplate plus POSListTemplateTag, POSListTemplates, POSListItemTemplate, POSListTemplateNode, POSListTemplateProp, POSListTemplateSegment, POSListRow, POSListRowClickEvent.
• components/POSList.d.ts (generated from pos-mobile meta.ts via pnpm build-extension-components:publish 2026-10) and the POSList blocks merged into components.d.ts. Only POSList additions are included; the pre-existing drift between the generator output and this repo's components.d.ts/components-shared.d.ts is left alone.
• components/targets/StandardComponents.ts — | 'POSList'.
• components/POSList/examples/{default,incremental-loading}.jsx.
• docs/.../2026-10/{generated_docs_data_v2.json,targets.json} regenerated with build-docs.mjs 2026-10.
• .changeset/pos-list-template-component.md (minor).

Verification

• yarn build, yarn type-check green; build/esm/surfaces/point-of-sale.mjs exports posListTemplate.
• loom test packages/ui-extensions/src/surfaces/point-of-sale/tests/pos-list-template — 16 tests: exact AST output for text placeholders, {{#if}} blocks, bind:, attribute segments, valueless attributes, type="text"; and every rejection above with its literal message.
• eslint clean on the changed files.

[ajanth-u]

/snapit

[shopify-github-actions-access]

🫰✨ Thanks @ajanth-u! Your snapshots have been published to npm.

Test the snapshots by updating your package.json with the newly published versions:

"@shopify/ui-extensions": "0.0.0-snapshot-20260912150820",
"@shopify/ui-extensions-tester": "0.0.0-snapshot-20260912150820"