Function ɵɵreplaceMetadata

packages/core/src/render3/hmr.ts:81–118

(
  type: Type<unknown>,
  applyMetadata: (...args: [Type<unknown>, unknown[], ...unknown[]]) => void,
  namespaces: unknown[],
  locals: unknown[],
  importMeta: ImportMetaExtended | null = null,
  id: string | null = null,
)

 * @codeGenApi
 */
export function ɵɵreplaceMetadata(
  type: Type<unknown>,
  applyMetadata: (...args: [Type<unknown>, unknown[], ...unknown[]]) => void,
  namespaces: unknown[],
  locals: unknown[],
  importMeta: ImportMetaExtended | null = null,
  id: string | null = null,
) {
  ngDevMode && assertComponentDef(type);
  const currentDef = getComponentDef(type)!;

  // The reason `applyMetadata` is a callback that is invoked (almost) immediately is because
  // the compiler usually produces more code than just the component definition, e.g. there
  // can be functions for embedded views, the variables for the constant pool and `setClassMetadata`
  // calls. The callback allows us to keep them isolate from the rest of the app and to invoke
  // them at the right time.
  applyMetadata.apply(null, [type, namespaces, ...locals]);

  const {newDef, oldDef} = mergeWithExistingDefinition(currentDef, getComponentDef(type)!);

  // TODO(crisbeto): the `applyMetadata` call above will replace the definition on the type.
  // Ideally we should adjust the compiler output so the metadata is returned, however that'll
  // require some internal changes. We re-add the metadata here manually.
  (type as any)[NG_COMP_DEF] = newDef;

  // If a `tView` hasn't been created yet, it means that this component hasn't been instantianted
  // before. In this case there's nothing left for us to do aside from patching it in.
  if (oldDef.tView) {
    const trackedViews = getTrackedLViews().values();
    for (const root of trackedViews) {
      // Note: we have the additional check, because `IsRoot` can also indicate
      // a component created through something like `createComponent`.
      if (isRootView(root) && root[PARENT] === null) {
        recreateMatchingLViews(importMeta, id, newDef, oldDef, root);
      }
    }
  }
}

/**
 * Merges two component definitions while preseving the original one in place.