$expand=permissions failed with notSupported error - microsoft-graph-api

Question

The documentation clearly states that this endpoint supports $expand to modify the search result:
users/{user-id}/drive/root/search(q='{search-text}')?$expand=permissions
But the request returns the following body in its response:
{
"error": {
"code": "notSupported",
"message": "The request is not supported by the system.",
"innerError": {
"request-id": "30fc9988-6f4f-46ba-a5b4-91b150c4a1a5",
"date": "2017-11-17T02:30:49"
}
}
}
This is also the case for other relationships. Though trying to expand createdByUser results in a BadRequest.
We want to do this request to avoid doing subsequent requests. Because at the moment we use a SharePoint ListItemUniqueId (due to backwards comparability) to find the corresponding DriveItem. Then we want to retrieve the permissions of this DriveItem. But right now we need to do two requests to achieve this.
We also can't use /users/{user-id}/drive/items because it does not support $filter.
Are we misunderstanding the docs or is this an issue on the Microsoft Graph side?

Answer 1

You cannot expand the permissions collection. From the documentation:
The permissions relationship of DriveItem cannot be expanded as part of a call to get DriveItem or a collection of DriveItems. You must access the permissions property directly.
The reason $expand=createdByUser returns a BadRequest is because it is already expanded by default.
Properties that are not supported are in $expand on the /search endpoint are:
children - Since /search returns files, this logically wouldn't make any sense here.
lastModifiedByUser - included by default
content - logically the content of each file wouldn't make sense to be included in a collection of DriveItems
Thumbnails can be expanded however ($expand=thumbnails).