Function navigateToNode

packages/core/src/hydration/node_lookup_utils.ts:224–268

* Helper function that navigates from a starting point node (the `from` node) * using provided set of navigation instructions (within `path` argument).

(from: Node, instructions: (number | NodeNavigationStep)[])

 * using provided set of navigation instructions (within `path` argument).
 */
function navigateToNode(from: Node, instructions: (number | NodeNavigationStep)[]): RNode {
  let node = from;
  for (let i = 0; i < instructions.length; i += 2) {
    const step = instructions[i];
    const repeat = instructions[i + 1] as number;
    for (let r = 0; r < repeat; r++) {
      if (ngDevMode && !node) {
        throw nodeNotFoundAtPathError(from, stringifyNavigationInstructions(instructions));
      }
      // `nodeNotFoundAtPathError` above would normally catch a missing node too, but it's
      // dev-mode only. Guard against it here so production throws a coded RuntimeError instead
      // of a raw TypeError when dereferencing `node` below.
      if (!node) {
        throw new RuntimeError(
          RuntimeErrorCode.HYDRATION_MISSING_NODE_ON_PATH,
          ngDevMode &&
            'During hydration Angular was unable to locate a node using a recorded navigation path. This usually means the client-rendered DOM no longer matches the server-rendered HTML.',
        );
      }
      switch (step) {
        case NODE_NAVIGATION_STEP_FIRST_CHILD:
          node = node.firstChild!;
          break;
        case NODE_NAVIGATION_STEP_NEXT_SIBLING:
          node = node.nextSibling!;
          break;
      }
    }
  }
  if (ngDevMode && !node) {
    throw nodeNotFoundAtPathError(from, stringifyNavigationInstructions(instructions));
  }
  // Same as above: `node` can legitimately end up null here (the path's last step ran off
  // the end of the real DOM) without the loop ever dereferencing it further, so the raw
  // TypeError guard above never gets a chance to fire for this case. Catch it here instead,
  // since this function's return type promises a non-null `RNode`.
  if (!node) {
    throw new RuntimeError(
      RuntimeErrorCode.HYDRATION_MISSING_NODE_ON_PATH,
      ngDevMode &&
        'During hydration Angular was unable to locate a node using a recorded navigation path. This usually means the client-rendered DOM no longer matches the server-rendered HTML.',
    );
  }
  return node as RNode;
}

/**
 * Locates an RNode given a set of navigation instructions (which also contains