pagination: activate page items with Space key

* Fixes page items not being activated by the "Space" key when
  focused via keyboard navigation. (closes #295)

* Page items are rendered by semantic-ui-react as anchors without
  href, with keyboard activation wired up manually for "Enter" only.
  Per the ARIA APG button pattern, elements behaving as buttons must
  be activatable with both "Enter" and "Space".

* Adds a custom pageItem render function that invokes the injected
  onClick on "Space" keydown, prevents the default page scroll, and
  adds role="button" for assistive technologies.

Author: SlimDumbledodge

src/lib/components/Pagination/Pagination.js

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2018-2022 CERN.
+ * SPDX-FileCopyrightText: 2018-2026 CERN.
  * SPDX-License-Identifier: MIT
  */
 
@@ -10,6 +10,21 @@ import { Pagination as Paginator } from "semantic-ui-react";
 import { AppContext } from "../ReactSearchKit";
 import { ShouldRender } from "../ShouldRender";
 
+const a11yPaginationItem = (Item, itemProps) => (
+  <Item
+    {...itemProps}
+    role="button"
+    onKeyDown={(event) => {
+      // ARIA button pattern: activate on "Space" in addition to "Enter".
+      // Mirrors the existing "Enter" handling in semantic-ui-react's PaginationItem.
+      if (event.key === " " && !itemProps.disabled) {
+        event.preventDefault(); // prevent page scroll
+        itemProps.onClick(event, itemProps);
+      }
+    }}
+  />
+);
+
 const defaultOptions = {
   boundaryRangeCount: 1,
   siblingRangeCount: 1,
@@ -141,6 +156,7 @@ const Element = ({
         lastItem={showLast ? undefined : null}
         prevItem={showPrev ? undefined : null}
         nextItem={showNext ? undefined : null}
+        pageItem={a11yPaginationItem}
         size={size}
         {...props}
       />

src/lib/components/Pagination/Pagination.test.js

@@ -0,0 +1,64 @@
+/*
+ * SPDX-FileCopyrightText: 2026 CERN.
+ * SPDX-License-Identifier: MIT
+ */
+import { mount } from "enzyme";
+import React from "react";
+import { AppContext } from "../ReactSearchKit/AppContext";
+import Pagination from "./Pagination";
+
+describe("test Pagination component", () => {
+  const mountPagination = (mockUpdateQueryPage) =>
+    mount(
+      <AppContext.Provider value={{ buildUID: (id) => id }}>
+        <Pagination
+          currentPage={1}
+          currentSize={10}
+          loading={false}
+          totalResults={50}
+          updateQueryPage={mockUpdateQueryPage}
+        />
+      </AppContext.Provider>
+    );
+
+  const findPageItem = (wrapper, page) =>
+    wrapper
+      .find("a.item")
+      .filterWhere(
+        (node) => node.prop("value") === page && node.prop("type") === "pageItem"
+      );
+
+  it("should change page when 'Space' is pressed on a page item", () => {
+    const mockUpdateQueryPage = jest.fn();
+    const mockPreventDefault = jest.fn();
+    const wrapper = mountPagination(mockUpdateQueryPage);
+
+    findPageItem(wrapper, 2).simulate("keydown", {
+      key: " ",
+      preventDefault: mockPreventDefault,
+    });
+
+    expect(mockUpdateQueryPage).toHaveBeenCalledWith(2);
+    // page scroll on "Space" should be prevented
+    expect(mockPreventDefault).toHaveBeenCalled();
+  });
+
+  it("should still change page when 'Enter' is pressed on a page item", () => {
+    const mockUpdateQueryPage = jest.fn();
+    const wrapper = mountPagination(mockUpdateQueryPage);
+
+    findPageItem(wrapper, 3).simulate("keydown", {
+      key: "Enter",
+      keyCode: 13,
+      which: 13,
+    });
+
+    expect(mockUpdateQueryPage).toHaveBeenCalledWith(3);
+  });
+
+  it("should expose page items with a 'button' role", () => {
+    const wrapper = mountPagination(jest.fn());
+
+    expect(findPageItem(wrapper, 2).prop("role")).toEqual("button");
+  });
+});