Function mergeTrivialChildren

packages/router/src/url_tree.ts:870–877

* When possible, merges the primary outlet child into the parent `UrlSegmentGroup`. * * When a segment group has only one child which is a primary outlet, merges that child into the * parent. That is, the child segment group's segments are merged into the `s` and the child's * children become th

(s: UrlSegmentGroup)

 * group into the parent.
 */
function mergeTrivialChildren(s: UrlSegmentGroup): UrlSegmentGroup {
  if (s.numberOfChildren === 1 && s.children[PRIMARY_OUTLET]) {
    const c = s.children[PRIMARY_OUTLET];
    return new UrlSegmentGroup(s.segments.concat(c.segments), c.children);
  }

  return s;
}

export function isUrlTree(v: any): v is UrlTree {
  return v instanceof UrlTree;