JsonApiResource always returning eager-loaded relationships on nested relations

[simon-tma]

Laravel Version

12.58.0 and 13.9.0

PHP Version

8.5.6

Database Driver & Version

No response

Description

JsonApiResource has the includePreviouslyLoadedRelationships() method to always include relationships that have been eager loaded, as well as those listed in include, with the default being to not to.

However, any nested relations that have been eager loaded are always being included if the intermediate relation is included.

Steps To Reproduce

class Post extends Model {
  public function comments(): HasMany { return $this->hasMany(Comment::class); }
}

class Comment extends Model {
  public function author(): BelongsTo { return $this->belongsTo(User::class); }
}

class CommentResource extends JsonApiResource {
  public $relationships = ['author'];
}

class PostResource extends JsonApiResource {
  public $relationships = ['comments'];
}

Router::get('/api/post/{post}', fn (Post $post) => new PostResource($post->load('comments.author));

curl localhost/api/post/1?include=comments

The return includes the author objects, even though not requested.

[prateekbhujel]

I updated #60123 to cover this too. The change keeps nested relationships scoped to the requested include path, so include=comments won't include comments.author just because it was eager loaded. If comments.author is requested, it still gets included.