This is a proposal of the enhanced custom function for Google Spreadsheet using Web Apps as the wrapper.
When the custom function is used, in the current specification, the most methods except several methods (for example, one of them is UrlFetchApp.) that the authorization is required cannot be used. So for example, when the filenames in the folder are retrieved from the folder name, unfortunately, this cannot be directly achieved. When this is tried, an error like
Exception: You do not have permission to call DriveApp.getFoldersByName. Required permissions: (https://www.googleapis.com/auth/drive.readonly || https://www.googleapis.com/auth/drive) occurs. From this situation, it is considered that when the authorization has already been done, the method that the authorization is required might be able to be used. In this report. I would like to introduce the method for using such methods by using Web Apps as the wrapper.
You can see the detail of this at https://github.com/tanaikech/Enhanced-Custom-Function-for-Google-Spreadsheet-using-Web-Apps-as-Wrapper