expose() returns a sentinel object, similar in spirit to NULL, that tells
the calling function to return its internal data structure. googledrive
stores a lot of information about the Drive API, MIME types, etc., internally
and then exploits it in helper functions, like drive_mime_type(),
drive_fields(), drive_endpoints(), etc. We use these objects to
provide nice defaults, check input validity, or lookup something cryptic,
like MIME type, based on something friendlier, like a file extension. Pass
expose() to such a function if you want to inspect its internal object, in
its full glory. This is inspired by the waiver() object in ggplot2.
expose()drive_mime_type(expose())
#> # A tibble: 78 × 5
#> mime_type ext description human_type default
#> <chr> <chr> <chr> <chr> <lgl>
#> 1 application/epub+zip NA NA NA NA
#> 2 application/msword doc NA doc TRUE
#> 3 application/msword dot NA dot FALSE
#> 4 application/pdf pdf NA pdf TRUE
#> 5 application/rtf rtf NA rtf TRUE
#> 6 application/vnd.google-apps.audio NA NA audio NA
#> 7 application/vnd.google-apps.document NA Google Docs document NA
#> 8 application/vnd.google-apps.drawing NA Google Drawing drawing NA
#> 9 application/vnd.google-apps.drive-sdk NA 3rd party sho… drive-sdk NA
#> 10 application/vnd.google-apps.file NA Google Drive … file NA
#> # ℹ 68 more rows
drive_fields(expose())
#> # A tibble: 55 × 2
#> name desc
#> <chr> <chr>
#> 1 appProperties "A collection of arbitrary key-value pairs whic…
#> 2 capabilities "Capabilities the current user has on this file…
#> 3 contentHints "Additional information about the content of th…
#> 4 copyRequiresWriterPermission "Whether the options to copy, print, or downloa…
#> 5 createdTime "The time at which the file was created (RFC 33…
#> 6 description "A short description of the file."
#> 7 driveId "ID of the shared drive the file resides in. On…
#> 8 explicitlyTrashed "Whether the file has been explicitly trashed, …
#> 9 exportLinks "Links for exporting Google Docs to specific fo…
#> 10 fileExtension "The final component of fullFileExtension. This…
#> # ℹ 45 more rows