nextjs-app/__tests__/components/SuggestList.test.tsx

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+import { render, screen } from '@testing-library/react';
+import { SuggestList, suggestOptionId } from '@/components/SuggestList';
+
+const ROWS = [
+  { urn: 1, school_name: "St Mary's Primary", local_authority: 'Camden',
+    postcode: 'NW1 1AA', phase: 'Primary', school_type: 'Voluntary aided school' },
+  { urn: 2, school_name: "St Mary's Primary", local_authority: 'Barnet',
+    postcode: 'EN5 2AA', phase: 'Primary', school_type: 'Community school' },
+];
+
+describe('SuggestList', () => {
+  it('is a listbox of options', () => {
+    render(<SuggestList id="s" suggestions={ROWS} activeIndex={-1}
+      onPick={() => {}} onHover={() => {}} />);
+    expect(screen.getByRole('listbox')).toBeInTheDocument();
+    expect(screen.getAllByRole('option')).toHaveLength(2);
+  });
+
+  it('shows the local authority, which is what tells two schools apart', () => {
+    // Both rows are "St Mary's Primary". Without the authority the list is
+    // unusable for exactly the query autosuggest exists to serve.
+    render(<SuggestList id="s" suggestions={ROWS} activeIndex={-1}
+      onPick={() => {}} onHover={() => {}} />);
+    expect(screen.getByText('Camden')).toBeInTheDocument();
+    expect(screen.getByText('Barnet')).toBeInTheDocument();
+  });
+
+  it('marks only the active option selected', () => {
+    render(<SuggestList id="s" suggestions={ROWS} activeIndex={1}
+      onPick={() => {}} onHover={() => {}} />);
+    const options = screen.getAllByRole('option');
+    expect(options[0]).toHaveAttribute('aria-selected', 'false');
+    expect(options[1]).toHaveAttribute('aria-selected', 'true');
+  });
+
+  it('gives each option the id the input will point at', () => {
+    // aria-activedescendant on the input has to name a real element id, or
+    // a screen reader announces nothing as the user arrows through.
+    render(<SuggestList id="s" suggestions={ROWS} activeIndex={0}
+      onPick={() => {}} onHover={() => {}} />);
+    expect(screen.getAllByRole('option')[0]).toHaveAttribute(
+      'id', suggestOptionId('s', 0));
+  });
+
+  it('renders nothing when there is nothing to suggest', () => {
+    const { container } = render(<SuggestList id="s" suggestions={[]}
+      activeIndex={-1} onPick={() => {}} onHover={() => {}} />);
+    expect(container).toBeEmptyDOMElement();
+  });
+});

nextjs-app/components/SuggestList.module.css

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+/*
+ * Anchored to .omniBoxContainer, which is position: relative for this reason.
+ *
+ * Every colour is a token, so the dropdown follows the theme. The dark theme
+ * redefines --bg-card, --border, --text-muted and --shadow-soft, and this
+ * inherits all four without a second rule.
+ */
+.list {
+  position: absolute;
+  top: calc(100% + 4px);
+  left: 0;
+  right: 0;
+  /* Above the sticky filter bar (10) and the hero layers (0–2), below the
+     skip-link (10000) and the modal overlay (1000). */
+  z-index: 40;
+  margin: 0;
+  padding: 4px;
+  list-style: none;
+  max-height: 320px;
+  overflow-y: auto;
+  background: var(--bg-card);
+  border: 1px solid var(--border);
+  border-radius: var(--radius-md);
+  box-shadow: var(--shadow-soft);
+}
+
+.option {
+  display: flex;
+  align-items: baseline;
+  justify-content: space-between;
+  gap: 12px;
+  padding: 10px 12px;
+  border-radius: var(--radius-sm);
+  cursor: pointer;
+  color: var(--text-primary);
+}
+
+/* Hover and keyboard share one style: the active option is the active option
+   however it became active. Two rules would drift. */
+.option:hover,
+.active {
+  background: var(--bg-secondary);
+}
+
+.name {
+  font-weight: 500;
+}
+
+.meta {
+  font-size: 0.85em;
+  color: var(--text-muted);
+  white-space: nowrap;
+}

nextjs-app/components/SuggestList.tsx

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+'use client';
+
+/**
+ * The autosuggest dropdown. Presentational only — it fetches nothing and owns
+ * no state, so the fetching rules and the ARIA rules can be read separately.
+ */
+
+import type { Suggestion } from '@/lib/suggest';
+import styles from './SuggestList.module.css';
+
+/** The id the input's aria-activedescendant points at. */
+export function suggestOptionId(id: string, index: number): string {
+  return `${id}-option-${index}`;
+}
+
+interface Props {
+  /** Shared with the input's aria-controls. */
+  id: string;
+  suggestions: Suggestion[];
+  activeIndex: number;
+  onPick: (s: Suggestion) => void;
+  onHover: (index: number) => void;
+}
+
+export function SuggestList({ id, suggestions, activeIndex, onPick, onHover }: Props) {
+  if (suggestions.length === 0) return null;
+
+  return (
+    <ul className={styles.list} id={id} role="listbox">
+      {suggestions.map((s, i) => (
+        <li
+          key={s.urn}
+          id={suggestOptionId(id, i)}
+          role="option"
+          aria-selected={i === activeIndex}
+          className={`${styles.option} ${i === activeIndex ? styles.active : ''}`}
+          /*
+           * onMouseDown, not onClick: the input's blur handler closes the list,
+           * and blur fires before click — so a click handler never runs. This
+           * is the classic autosuggest bug where the dropdown is unclickable
+           * with a mouse while working perfectly with a keyboard.
+           */
+          onMouseDown={(e) => { e.preventDefault(); onPick(s); }}
+          onMouseEnter={() => onHover(i)}
+        >
+          <span className={styles.name}>{s.school_name}</span>
+          {/* Not decoration: there are many "St Mary's". */}
+          <span className={styles.meta}>{s.local_authority}</span>
+        </li>
+      ))}
+    </ul>
+  );
+}