Function calcPathForNode

packages/core/src/hydration/node_lookup_utils.ts:324–399

(
  tNode: TNode,
  lView: LView,
  excludedParentNodes: Set<number> | null,
)

 * instructions needs to be generated for a TNode.
 */
export function calcPathForNode(
  tNode: TNode,
  lView: LView,
  excludedParentNodes: Set<number> | null,
): string {
  let parentTNode = tNode.parent;
  let parentIndex: number | string;
  let parentRNode: RNode;
  let referenceNodeName: string;

  // Skip over all parent nodes that are disconnected from the DOM, such nodes
  // can not be used as anchors.
  //
  // This might happen in certain content projection-based use-cases, where
  // a content of an element is projected and used, when a parent element
  // itself remains detached from DOM. In this scenario we try to find a parent
  // element that is attached to DOM and can act as an anchor instead.
  //
  // It can also happen that the parent node should be excluded, for example,
  // because it belongs to an i18n block, which requires paths which aren't
  // relative to other views in an i18n block.
  while (
    parentTNode !== null &&
    (isDisconnectedNode(parentTNode, lView) || excludedParentNodes?.has(parentTNode.index))
  ) {
    parentTNode = parentTNode.parent;
  }

  if (parentTNode === null || !(parentTNode.type & TNodeType.AnyRNode)) {
    // If there is no parent TNode or a parent TNode does not represent an RNode
    // (i.e. not a DOM node), use component host element as a reference node.
    parentIndex = referenceNodeName = REFERENCE_NODE_HOST;
    parentRNode = lView[DECLARATION_COMPONENT_VIEW][HOST]!;
  } else {
    // Use parent TNode as a reference node.
    parentIndex = parentTNode.index;
    parentRNode = unwrapRNode(lView[parentIndex]);
    referenceNodeName = renderStringify(parentIndex - HEADER_OFFSET);
  }
  let rNode = unwrapRNode(lView[tNode.index]);
  if (tNode.type & (TNodeType.AnyContainer | TNodeType.Icu)) {
    // For <ng-container> nodes, instead of serializing a reference
    // to the anchor comment node, serialize a location of the first
    // DOM element. Paired with the container size (serialized as a part
    // of `ngh.containers`), it should give enough information for runtime
    // to hydrate nodes in this container.
    const firstRNode = getFirstNativeNode(lView, tNode);

    // If container is not empty, use a reference to the first element,
    // otherwise, rNode would point to an anchor comment node.
    if (firstRNode) {
      rNode = firstRNode;
    }
  }
  let path: string | null = calcPathBetween(parentRNode as Node, rNode as Node, referenceNodeName);
  if (path === null && parentRNode !== rNode) {
    // Searching for a path between elements within a host node failed.
    // Trying to find a path to an element starting from the `document.body` instead.