fix(showcase): the invoice print page heads its line-items table with labels, not field names

examples/app-showcase/src/ui/pages/invoice-document.page.ts

@@ -57,7 +57,19 @@ export const InvoiceDocumentPage = definePage({
           properties: {
             childObject: 'showcase_invoice_line',
             relationshipField: 'invoice',
-            columns: [{ name: 'description' }, { name: 'quantity' }, { name: 'unit_price' }, { name: 'amount' }],
+            // Each column declares its heading. Unlike the master-detail grid
+            // (`showcase_invoice.lines.inlineColumns`), this block does not
+            // fill a column from the child field, so an identity-only
+            // `{ name }` column prints its raw field name. The labels are the
+            // invoice line fields' own. They read in English in every locale:
+            // a column `label` is a plain string, and no translation bundle
+            // key reaches a `record:line_items` column.
+            columns: [
+              { name: 'description', label: 'Description' },
+              { name: 'quantity', label: 'Qty' },
+              { name: 'unit_price', label: 'Unit Price' },
+              { name: 'amount', label: 'Amount' },
+            ],
             readonly: true,
           },
         },

examples/app-showcase/test/invoice-document-line-items.test.ts

@@ -0,0 +1,62 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+import { describe, it, expect } from 'vitest';
+import { RecordLineItemsProps } from '@objectstack/spec/ui';
+
+import { InvoiceDocumentPage } from '../src/ui/pages/index.js';
+import { InvoiceLine } from '../src/data/objects/invoice.object.js';
+
+/**
+ * The invoice print page heads its line-items table with labels.
+ *
+ * `record:line_items` draws a column exactly as declared. Unlike the
+ * master-detail grid, it does not fill a column from the child object's
+ * field, so a column with no `label` is headed by its raw field name: the
+ * printed invoice read `description` / `quantity` / `unit_price` / `amount`.
+ *
+ * The pin holds each column to the label its own child field declares, and
+ * never to the field name. Deriving the expected heading from the field keeps
+ * the print in step with the master-detail grid, which hydrates the same
+ * labels for the same fields.
+ */
+
+type Column = Record<string, unknown>;
+type Component = { type?: unknown; properties?: Record<string, unknown> };
+
+const page = InvoiceDocumentPage as unknown as { regions?: { components?: Component[] }[] };
+
+const lineItemBlocks = (page.regions ?? [])
+  .flatMap((region) => region.components ?? [])
+  .filter((component) => component.type === 'record:line_items');
+
+const columnsOf = (block: Component | undefined): Column[] =>
+  (Array.isArray(block?.properties?.columns) ? block!.properties!.columns : []) as Column[];
+
+const childFields = (InvoiceLine.fields ?? {}) as Record<string, { label?: unknown }>;
+
+describe('Invoice print page — the line-items table is headed by labels, not field names', () => {
+  const [block, ...rest] = lineItemBlocks;
+
+  it('carries one line-items block over the invoice lines', () => {
+    expect(block, 'the invoice print page must carry its line-items table').toBeTruthy();
+    expect(rest).toHaveLength(0);
+    expect(block.properties?.childObject).toBe(InvoiceLine.name);
+    expect(columnsOf(block).map((c) => c.name)).toEqual(['description', 'quantity', 'unit_price', 'amount']);
+  });
+
+  it('heads every column with its child field\'s own label, never the field name', () => {
+    for (const column of columnsOf(block)) {
+      const name = column.name as string;
+      const fieldLabel = childFields[name]?.label;
+      expect(typeof fieldLabel, `showcase_invoice_line.${name} must declare a label`).toBe('string');
+      expect(column.label, `column '${name}' must declare its heading`).toBe(fieldLabel);
+      expect(column.label, `column '${name}' must not be headed by its field name`).not.toBe(name);
+    }
+  });
+
+  it('parses against the spec\'s `record:line_items` row with the labels intact', () => {
+    const result = RecordLineItemsProps.safeParse(block.properties);
+    expect(result.success, JSON.stringify(result.error?.issues)).toBe(true);
+    expect(result.data).toEqual(block.properties);
+  });
+});