Laravel resource ignoring given fields - laravel

Question

I'm trying to convert a given API response in something easy to work with.
This is what I have so far:
Controller:
public function drive()
{
$optParams = [
'corpora' => 'drive',
'driveId' => env('GOOGLE_DRIVE_ID'),
'includeItemsFromAllDrives' => true,
'supportsAllDrives' => true,
'fields' => 'files(*)'
];
$results = $this->googleDrive->files->listFiles($optParams);
$data = collect($results);
$collection = new FileCollection($data);
dd($collection);
return 'Hi!';
}
FileCollection resource:
public function toArray($request)
{
return [
'data' => $this->collection,
'meta' => ['files_count' => $this->collection->count()],
];
}
File resource:
public function toArray($request)
{
return [
'name' => $this->resource['name'],
'mime' => $this->resource['mimeType'],
'parents' => $this->resource['parents'],
'version' => $this->resource['version'],
'webDownloadLink' => $this->resource['webContentLink'],
'webLink' => $this->resource['webViewLink'],
'modified_at' => $this->resource['modifiedTime'],
'size' => $this->resource['size']
];
}
This is the result I'm getting:
FileCollection {#223 ▼
+collects: null
+collection: Collection {#243 ▶}
+resource: Collection {#243 ▼
#items: array:2 [▼
0 => File {#224 ▼
+resource: Google_Service_Drive_DriveFile {#279 ▶}
+with: []
+additional: []
}
1 => File {#263 ▼
+resource: Google_Service_Drive_DriveFile {#269 ▶}
+with: []
+additional: []
}
]
}
+with: []
+additional: []
}
So as you can see the types of resources are correct, but for some reason the 'meta' in the FileCollection isn't there, nor are the fields in the File resource. All fields are still shown, like 30+ (instead of the 8 requested in the FileResource).
Am I missing something here?
EDIT:
When accessing the collection with the toArray() method ($collection->toArray(null)), I do indeed get the appropriate result:
array:2 [▼
"data" => Collection {#243 ▼
#items: array:2 [▼
0 => File {#224 ▶}
1 => File {#263 ▶}
]
}
"meta" => array:1 [▼
"files_count" => 2
]
]
So how do I make sure now that this collection uses the toArray() of the FileResources? (I'm still getting over 30 fields, instead of 8).
PS: I don't really get why I need to call the toArray(), nowhere in their documentation is it written : https://laravel.com/docs/5.8/eloquent-resources .