The /{post-id}/sharedposts edge does exist; but you won’t be able to get any shares made by users, unless those were users of your app as well, and granted it user_posts
permission to read their posts.
So unless in very specific scenarios, like f.e. where you had a website community of people that are using your app and granted it the permission, and they share each other’s stuff, you likely won’t be able to get much here.
Shares made by pages are probably different, you might be able to get those post IDs. But then you won’t be able to get any further info about those posts, unless your app has the Page Public Content Access feature approved (and the allowed use cases for that are very limited, so Facebook will likely not grant it in review for such a purpose.)
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…