How to add my custom page resolver instead of Spartacus page resolver?

Question

I'm adding my resolver (which extended from PageMetaResolver) into providers in my own home.module. However, my method 'resolve' is not called. Have you got any ideas?

@Injectable({
  providedIn: 'root'
})
export class HomePageMetaResolver extends PageMetaResolver implements PageDescriptionResolver {

  constructor(
    protected routingService: RoutingService,
    protected translationService: TranslationService,
    protected cms: CmsService
  ) {
    super();
    this.pageType = PageType.CONTENT_PAGE;
  }

  resolve(): Observable<PageMeta> {
    console.log('RESOLVE')

    return this.cms.getCurrentPage().pipe(
      switchMap(page =>
        combineLatest([
          this.resolveDescription()
        ])
      ),
      map(([description]) => ({ description }))
    );
  }

  resolveDescription(): Observable<string> {
    return new Observable(sub => {
      sub.next('test description');
    });
  }
}

Answer 1

TL;DR

Please specify not only this.pageType, but also this.pageTemplate for your PageMetaResolver.

---

Detailed explanation

The most specific Page Meta Resolver wins

Guessing from the name of your meta resolver, you want to provide custom meta only for your Home page. Please note that the most specific meta resolver wins thanks to the simple scoring algorithm, which takes into consideration 2 factors: page type and page template (see source https://github.com/SAP/cloud-commerce-spartacus-storefront/blob/develop/projects/core/src/cms/page/page-meta.resolver.ts#L11).

Currently your resolver HomePageMetaResolver has the same specificity as the generic one so your resolve method is not called.

You need to specify more your meta resolver by defining its property this.pageTemplate = '<name-of-page-template-used-only-at-homepage>'. Then your HomePageMetaResolver will get higher score than a default ContentPageMetaResolver whenever you visit a homepage.

Custom scoring algorithms

For custom scoring algorithms (which could take pageId into account, for instance), you can overwrite the method getScore of your PageMetaResolvers. You can even extend the method PageMetaService.getMetaResolver to redefine all rules of chosing the right page meta resolver. But for your case the standard solution (described above) should suffice.