How to configure the relationship of 2 custom modules?

[qFlensT]

Suppose I have 2 custom modules - site-content and product-banner, for which I want to build many-to-many relationship:

src/
└── modules/
    ├── product-banner
    └── site-content

SiteContent model schema:

{
  id: model.id().primaryKey(),
  name: model.text(),
  page_key: model.enum([...PAGE_KEYS]),
  is_active: model.boolean().default(false),
  home_page_configuration: model.hasOne(() => HomePageConfiguration).nullable(),
  product_banners: model.manyToMany(() => ProductBanner, {
    mappedBy: "site_contents",
    joinColumn: "site_content_id",
    inverseJoinColumn: "product_banner_id",
  }),
}

ProductBanner model schema:

{
  id: model.id().primaryKey(),
  title: model.text().nullable(),
  subtitle: model.text().nullable(),
  description: model.text().nullable(),
  image_url: model.text(),
  categories: model.manyToMany(() => ProductBannerCategory, {
    mappedBy: "product_banners",
  }),
  site_contents: model.manyToMany(() => ProductBanner, {
    mappedBy: "product_banners"
  }),
}

But with this approach, I get an error when calling npx medusa db:generate site_content product_banner:

error:   Entity 'ProductBanner' was not discovered, please make sure to provide it in 'entities' array when initializing the ORM (used in SiteContent.product_banners)

After some time, I came to the conclusion that I should try using a link directory. I deleted the fields with the link records of these entities (product_banners and site_contents) and created the following file:

export default defineLink(
  {
    linkable: SiteContentModule.linkable.siteContent,
    isList: true,
  },
  {
    linkable: ProductBannerModule.linkable.productBanner,
    isList: true,
  }
);

With this approach the migrations were successfully created, but I am not sure if this approach is correct as it is not described in the documentation.

[olivermrbl]

@qFlensT, this is the correct approach for associating models across modules. Modules Links are documented here. We would be curious to know what you felt missing in the documentation about this topic.

[qFlensT]

Sorry, I was blind 🫥