fix: hide XBRL hypercube scaffolding rows (Table / Line Items)

Stripping the role tags exposed that us-gaap:StatementTable and
us-gaap:StatementLineItems render as bare, duplicated 'Statement'
header rows — pure hypercube plumbing that carries no facts and is not
a meaningful heading. Skip these abstracts in the pivot row walk and
keep their children at the current depth so the tree stays flat.

The check keys off the concept's local name (…Table / …LineItems),
which is identical whether elements are keyed by IRI (store/holon
route) or qname (SEC route), so both rendering routes hide them the
same way. Axis/Domain/Member/Abstract/Roll Forward rows are unchanged.

Author: jfrench9

src/pivot.ts

@@ -231,6 +231,20 @@ function fallbackElement(id: string): ElementInfo {
 const elementOf = (model: NormalizedReport, id: string): ElementInfo =>
   model.elements[id] ?? fallbackElement(id)
 
+/**
+ * Pure XBRL hypercube plumbing: a `[Table]` (the hypercube itself) and its
+ * `[Line Items]` container. These abstracts exist only to hang dimensional facts
+ * off of — they carry no data, and once their role tag is stripped for display
+ * they collapse to a bare, duplicated "Statement" heading. So they are never a
+ * meaningful row: skip the header and promote their children in their place.
+ * Keyed off the concept's local name (identical across the store and SEC routes,
+ * which key elements by IRI vs qname respectively) so both render the same.
+ */
+const SCAFFOLD_LOCAL_RE = /(?:Table|LineItems)$/
+function isStructuralScaffold(el: ElementInfo): boolean {
+  return el.abstract && SCAFFOLD_LOCAL_RE.test(localName(el.qname))
+}
+
 // ── Default configuration ───────────────────────────────────────────────────
 
 /**
@@ -711,7 +725,10 @@ export function buildPivot(
     seenInTree.add(id)
     const el = elementOf(model, id)
     if (el.abstract) {
-      if (config.showAbstracts) {
+      // Hypercube scaffolding ([Table]/[Line Items]) is not a heading — hide its
+      // row and keep its children at the current depth so the tree stays flat.
+      const scaffold = isStructuralScaffold(el)
+      if (config.showAbstracts && !scaffold) {
         rows.push({
           key: id,
           element: el,
@@ -722,7 +739,8 @@ export function buildPivot(
           cells: [],
         })
       }
-      for (const child of tree.childrenOf.get(id) ?? []) walk(child, depth + 1)
+      const childDepth = scaffold ? depth : depth + 1
+      for (const child of tree.childrenOf.get(id) ?? []) walk(child, childDepth)
     } else {
       for (const child of tree.childrenOf.get(id) ?? []) walk(child, depth + 1)
       emitConcept(id, depth)

test/pivot.test.ts

@@ -444,6 +444,84 @@ describe('buildPivot — incomplete period columns are dropped', () => {
   })
 })
 
+describe('buildPivot — hides XBRL hypercube scaffolding rows', () => {
+  // A [Table] and its [Line Items] container sit between the section header and
+  // the real concepts. They carry no facts and (once their role tag is stripped)
+  // read as bare, duplicated "Statement" — pure plumbing, not headings. Elements
+  // are keyed by qname here, mirroring the SEC route (the store route keys by
+  // IRI); the scaffold check keys off the local name so both behave identically.
+  const SEC_ABS = 'us-gaap:IncomeStatementAbstract'
+  const TABLE = 'us-gaap:StatementTable'
+  const LINEITEMS = 'us-gaap:StatementLineItems'
+  const REV = 'us-gaap:Revenues'
+
+  function scaffoldReport(): NormalizedReport {
+    fid = 0
+    return {
+      reportId: 'r',
+      reportIri: null,
+      entity: null,
+      informationBlocks: [
+        { id: 's', blockType: 'income_statement', factSet: 'fs', label: null, structureId: 's' },
+      ],
+      structures: [
+        {
+          id: 's',
+          blockType: 'income_statement',
+          roleUri: null,
+          structureName: 'Income',
+          order: 0,
+        },
+      ],
+      facts: [fact(REV, 'p', 383285000000)],
+      elements: {
+        [SEC_ABS]: el(SEC_ABS, { abstract: true }),
+        [TABLE]: el(TABLE, { abstract: true }),
+        [LINEITEMS]: el(LINEITEMS, { abstract: true }),
+        [REV]: el(REV, { monetary: true, periodType: 'duration', numericKind: 'monetary' }),
+      },
+      periods: {
+        p: {
+          id: 'p',
+          type: 'duration',
+          instant: null,
+          startDate: '2022-09-25',
+          endDate: '2023-09-30',
+          end: '2023-09-30',
+        },
+      },
+      units: { 'u:usd': { id: 'u:usd', measure: 'iso4217:USD', label: 'USD', symbol: '$' } },
+      calcAssociations: [],
+      presAssociations: [
+        { parent: SEC_ABS, child: TABLE, order: 0, role: null, structure: 's' },
+        { parent: TABLE, child: LINEITEMS, order: 0, role: null, structure: 's' },
+        { parent: LINEITEMS, child: REV, order: 0, role: null, structure: 's' },
+      ],
+    }
+  }
+
+  const p = buildPivot(scaffoldReport(), scaffoldReport().informationBlocks[0])
+
+  it('emits no header row for the [Table]/[Line Items] plumbing', () => {
+    const scaffold = p.rows.filter(
+      (r) => r.header && /(?:Table|LineItems)$/.test(r.element.qname.split(':').pop() ?? '')
+    )
+    expect(scaffold).toHaveLength(0)
+  })
+
+  it('keeps the real section header and the concepts below it', () => {
+    expect(rowByKey(p, SEC_ABS)?.header).toBe(true)
+    expect(rowByKey(p, REV)?.cells?.[0]?.value).toBe(383285000000)
+  })
+
+  it('promotes the concepts to the scaffold’s depth instead of over-indenting', () => {
+    // Section header at 0; the two scaffold levels are skipped, so Revenues lands
+    // at depth 1 — not depth 3 (header + [Table] + [Line Items]).
+    expect(rowByKey(p, SEC_ABS)?.depth).toBe(0)
+    expect(rowByKey(p, REV)?.depth).toBe(1)
+  })
+})
+
 describe('buildPivot — a member-only concept gets a heading row (dims as rows)', () => {
   // A detail disclosure: a concept reported only per-member, with no consolidated
   // total. Its member rows must not be orphaned "member-only" labels — a valueless