Function annotateHostElementForHydration

packages/core/src/hydration/annotate.ts:820–844

* Annotates component host element for hydration: * - by either adding the `ngh` attribute and collecting hydration-related info * for the serialization and transferring to the client * - or by adding the `ngSkipHydration` attribute in case Angular detects that * component contents is not co

(
  element: RElement,
  lView: LView,
  parentDeferBlockId: string | null,
  context: HydrationContext,
)

 *          or `null` when a given component can not be serialized.
 */
function annotateHostElementForHydration(
  element: RElement,
  lView: LView,
  parentDeferBlockId: string | null,
  context: HydrationContext,
): number | null {
  const renderer = lView[RENDERER];
  if (
    (hasI18n(lView) && !isI18nHydrationSupportEnabled()) ||
    componentUsesShadowDomEncapsulation(lView)
  ) {
    // Attach the skip hydration attribute if this component:
    // - either has i18n blocks, since hydrating such blocks is not yet supported
    // - or uses ShadowDom view encapsulation, since Domino doesn't support
    //   shadow DOM, so we can not guarantee that client and server representations
    //   would exactly match
    renderer.setAttribute(element, SKIP_HYDRATION_ATTR_NAME, '');
    return null;
  } else {
    const ngh = serializeLView(lView, parentDeferBlockId, context);
    const index = context.serializedViewCollection.add(ngh);
    renderer.setAttribute(element, NGH_ATTR_NAME, index.toString());
    return index;
  }
}

/**
 * Annotates defer block comment node for hydration: