From 4af49cd4f1b18e0e2688c3db47ec54c8887657a2 Mon Sep 17 00:00:00 2001
From: "Frank Pigeon Jr." <4629398+fpigeonjr@users.noreply.github.com>
Date: Tue, 1 Sep 2026 12:06:41 -0500
Subject: [PATCH 1/2] Fix AbstractRow rowheaders/columnheaders no-op concat

_setRowHeaders discarded the result of Array.prototype.concat instead
of assigning it, so the public rowheaders/columnheaders collections on
AbstractRow were always empty regardless of the row's actual DOM
content. Assign the concat result back to the properties, and add a
spec asserting the header collections are populated correctly.

Fixes #658
---
 .../aria/abstract-grid/abstract-row.spec.ts        | 14 ++++++++++++++
 .../aria/abstract-grid/abstract-row.ts             |  4 ++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/ui-kit/experimental/aria/abstract-grid/abstract-row.spec.ts b/src/ui-kit/experimental/aria/abstract-grid/abstract-row.spec.ts
index a32dbdad4..0055d55d8 100644
--- a/src/ui-kit/experimental/aria/abstract-grid/abstract-row.spec.ts
+++ b/src/ui-kit/experimental/aria/abstract-grid/abstract-row.spec.ts
@@ -35,6 +35,20 @@ describe("AbstractRow", () => {
     ]);
   });
 
+  it("populates rowheaders and columnheaders with their respective cells", () => {
+    const row = buildRow([
+      { role: "columnheader", key: "col" },
+      { role: "rowheader", key: "row" },
+      { role: "gridcell", key: "a" },
+      { role: "gridcell", key: "b" },
+    ]);
+
+    const abstractRow = new AbstractRow(row);
+
+    expect(abstractRow.rowheaders.map((c) => c.key)).toEqual(["row"]);
+    expect(abstractRow.columnheaders.map((c) => c.key)).toEqual(["col"]);
+  });
+
   it("addCell appends a cell to the cells collection", () => {
     const row = buildRow([{ role: "gridcell", key: "a" }]);
     const abstractRow = new AbstractRow(row);
diff --git a/src/ui-kit/experimental/aria/abstract-grid/abstract-row.ts b/src/ui-kit/experimental/aria/abstract-grid/abstract-row.ts
index 538f9cef6..eec5119d6 100755
--- a/src/ui-kit/experimental/aria/abstract-grid/abstract-row.ts
+++ b/src/ui-kit/experimental/aria/abstract-grid/abstract-row.ts
@@ -43,9 +43,9 @@ export class AbstractRow {
 
   private _setRowHeaders(cells: AbstractCell[], role: CellRole): void {
     if (role === "rowheader") {
-      this.rowheaders.concat(cells);
+      this.rowheaders = this.rowheaders.concat(cells);
     } else if (role === "columnheader") {
-      this.columnheaders.concat(cells);
+      this.columnheaders = this.columnheaders.concat(cells);
     } else {
       return;
     }

From a4b75b2e1c49dd85a99d7d6adcaf0037c2700780 Mon Sep 17 00:00:00 2001
From: "Frank Pigeon Jr." <4629398+fpigeonjr@users.noreply.github.com>
Date: Tue, 1 Sep 2026 12:22:29 -0500
Subject: [PATCH 2/2] Reuse the same AbstractCell instances in cells and header
 collections
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

_findCells called _getCellsByRole twice per role — once to build the
header collections via _setRowHeaders, and again to build the
accumulator returned as cells. Each call constructs new AbstractCell
instances, which also register duplicate keydown/click listeners on
every header DOM node. Reuse the already-created cells value in the
reducer so rowheaders/columnheaders are true subsets of cells and each
node is initialized exactly once.

Addresses Copilot review comment on PR #671.
---
 .../aria/abstract-grid/abstract-row.spec.ts      | 16 ++++++++++++++++
 .../aria/abstract-grid/abstract-row.ts           |  2 +-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/ui-kit/experimental/aria/abstract-grid/abstract-row.spec.ts b/src/ui-kit/experimental/aria/abstract-grid/abstract-row.spec.ts
index 0055d55d8..232a96b8f 100644
--- a/src/ui-kit/experimental/aria/abstract-grid/abstract-row.spec.ts
+++ b/src/ui-kit/experimental/aria/abstract-grid/abstract-row.spec.ts
@@ -49,6 +49,22 @@ describe("AbstractRow", () => {
     expect(abstractRow.columnheaders.map((c) => c.key)).toEqual(["col"]);
   });
 
+  it("reuses the same AbstractCell instances in rowheaders/columnheaders as in cells", () => {
+    const row = buildRow([
+      { role: "columnheader", key: "col" },
+      { role: "rowheader", key: "row" },
+      { role: "gridcell", key: "a" },
+    ]);
+
+    const abstractRow = new AbstractRow(row);
+
+    const rowheaderInCells = abstractRow.cells.find((c) => c.key === "row");
+    const columnheaderInCells = abstractRow.cells.find((c) => c.key === "col");
+
+    expect(abstractRow.rowheaders[0]).toBe(rowheaderInCells);
+    expect(abstractRow.columnheaders[0]).toBe(columnheaderInCells);
+  });
+
   it("addCell appends a cell to the cells collection", () => {
     const row = buildRow([{ role: "gridcell", key: "a" }]);
     const abstractRow = new AbstractRow(row);
diff --git a/src/ui-kit/experimental/aria/abstract-grid/abstract-row.ts b/src/ui-kit/experimental/aria/abstract-grid/abstract-row.ts
index eec5119d6..c8636d739 100755
--- a/src/ui-kit/experimental/aria/abstract-grid/abstract-row.ts
+++ b/src/ui-kit/experimental/aria/abstract-grid/abstract-row.ts
@@ -24,7 +24,7 @@ export class AbstractRow {
 
       this._setRowHeaders(cells, role);
 
-      return accumulator.concat(this._getCellsByRole(node, role));
+      return accumulator.concat(cells);
     }, []);
   }