Function getStemVariants

src/search/query-utils.ts:85–142

(term: string)

 * Stems are used as PREFIX matches in FTS, so they don't need to be perfect English words.
 */
export function getStemVariants(term: string): string[] {
  const variants = new Set<string>();
  const t = term.toLowerCase();

  // -ing: caching→cach/cache, handling→handl/handle, running→run
  if (t.endsWith('ing') && t.length > 5) {
    const base = t.slice(0, -3);
    variants.add(base);
    variants.add(base + 'e');
    if (base.length >= 2 && base[base.length - 1] === base[base.length - 2]) {
      variants.add(base.slice(0, -1));
    }
  }

  // -tion/-sion: eviction→evict, expression→express
  if ((t.endsWith('tion') || t.endsWith('sion')) && t.length > 5) {
    variants.add(t.slice(0, -3));
  }

  // -ment: management→manage
  if (t.endsWith('ment') && t.length > 6) {
    variants.add(t.slice(0, -4));
  }

  // -ies: entries→entry
  if (t.endsWith('ies') && t.length > 4) {
    variants.add(t.slice(0, -3) + 'y');
  }
  // -es: processes→process, classes→class
  else if (t.endsWith('es') && t.length > 4) {
    variants.add(t.slice(0, -2));
  }
  // -s: errors→error (skip -ss endings like "class")
  else if (t.endsWith('s') && !t.endsWith('ss') && t.length > 4) {
    variants.add(t.slice(0, -1));
  }

  // -ed: handled→handle, propagated→propagate, carried→carry
  if (t.endsWith('ed') && !t.endsWith('eed') && t.length > 4) {
    variants.add(t.slice(0, -1));
    variants.add(t.slice(0, -2));
    if (t.endsWith('ied') && t.length > 5) {
      variants.add(t.slice(0, -3) + 'y');
    }
  }

  // -er: builder→build/builde, handler→handl/handle, getter→get
  if (t.endsWith('er') && t.length > 4) {
    const base = t.slice(0, -2);
    variants.add(base);
    variants.add(base + 'e');
    if (base.length >= 2 && base[base.length - 1] === base[base.length - 2]) {
      variants.add(base.slice(0, -1));
    }
  }

  return [...variants].filter(v => v.length >= 3 && v !== t);
}