Function updateSegmentGroupChildren

packages/router/src/create_url_tree.ts:414–476

(
  segmentGroup: UrlSegmentGroup,
  startIndex: number,
  commands: readonly any[],
)

}

function updateSegmentGroupChildren(
  segmentGroup: UrlSegmentGroup,
  startIndex: number,
  commands: readonly any[],
): UrlSegmentGroup {
  if (commands.length === 0) {
    return new UrlSegmentGroup(segmentGroup.segments, {});
  } else {
    const outlets = getOutlets(commands);
    // Keyed by outlet name, which can be `__proto__`, so use a null-prototype map.
    const children: {[key: string]: UrlSegmentGroup} = Object.create(null);
    // If the set of commands applies to anything other than the primary outlet and the child
    // segment is an empty path primary segment on its own, we want to apply the commands to the
    // empty child path rather than here. The outcome is that the empty primary child is effectively
    // removed from the final output UrlTree. Imagine the following config:
    //
    // {path: '', children: [{path: '**', outlet: 'popup'}]}.
    //
    // Navigation to /(popup:a) will activate the child outlet correctly Given a follow-up
    // navigation with commands
    // ['/', {outlets: {'popup': 'b'}}], we _would not_ want to apply the outlet commands to the
    // root segment because that would result in
    // //(popup:a)(popup:b) since the outlet command got applied one level above where it appears in
    // the `ActivatedRoute` rather than updating the existing one.
    //
    // Because empty paths do not appear in the URL segments and the fact that the segments used in
    // the output `UrlTree` are squashed to eliminate these empty paths where possible
    // https://github.com/angular/angular/blob/13f10de40e25c6900ca55bd83b36bd533dacfa9e/packages/router/src/url_tree.ts#L755
    // it can be hard to determine what is the right thing to do when applying commands to a
    // `UrlSegmentGroup` that is created from an "unsquashed"/expanded `ActivatedRoute` tree.
    // This code effectively "squashes" empty path primary routes when they have no siblings on
    // the same level of the tree.
    if (
      Object.keys(outlets).some((o) => o !== PRIMARY_OUTLET) &&
      segmentGroup.children[PRIMARY_OUTLET] &&
      segmentGroup.numberOfChildren === 1 &&
      segmentGroup.children[PRIMARY_OUTLET].segments.length === 0
    ) {
      const childrenOfEmptyChild = updateSegmentGroupChildren(
        segmentGroup.children[PRIMARY_OUTLET],
        startIndex,
        commands,
      );
      return new UrlSegmentGroup(segmentGroup.segments, childrenOfEmptyChild.children);
    }

    Object.entries(outlets).forEach(([outlet, commands]) => {
      if (typeof commands === 'string') {
        commands = [commands];
      }
      if (commands !== null) {
        children[outlet] = updateSegmentGroup(segmentGroup.children[outlet], startIndex, commands);
      }
    });

    Object.entries(segmentGroup.children).forEach(([childOutlet, child]) => {
      if (outlets[childOutlet] === undefined) {
        children[childOutlet] = child;