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: 89 × 5
#> mime_type ext description human_type default
#> <chr> <chr> <chr> <chr> <lgl>
#> 1 application/epub+zip epub NA epub FALSE
#> 2 application/msword doc NA doc TRUE
#> 3 application/pdf pdf NA pdf TRUE
#> 4 application/rtf rtf NA rtf TRUE
#> 5 application/vnd.google-apps.audio NA NA audio NA
#> 6 application/vnd.google-apps.document NA Google Docs document NA
#> 7 application/vnd.google-apps.drawing NA Google Drawin… drawing NA
#> 8 application/vnd.google-apps.drive-sdk NA Third-party s… drive-sdk NA
#> 9 application/vnd.google-apps.file NA Google Drive … file NA
#> 10 application/vnd.google-apps.folder NA Google Drive … folder NA
#> # ℹ 79 more rows
drive_fields(expose())
#> # A tibble: 64 × 2
#> name desc
#> <chr> <chr>
#> 1 appProperties "A collection of arbitrary key-value pairs whic…
#> 2 capabilities "Output only. Capabilities the current user has…
#> 3 contentHints "Additional information about the content of th…
#> 4 contentRestrictions "Restrictions for accessing the content of the …
#> 5 copyRequiresWriterPermission "Whether the options to copy, print, or downloa…
#> 6 createdTime "The time at which the file was created (RFC 33…
#> 7 description "A short description of the file."
#> 8 downloadRestrictions "Download restrictions applied on the file."
#> 9 driveId "Output only. ID of the shared drive the file r…
#> 10 explicitlyTrashed "Output only. Whether the file has been explici…
#> # ℹ 54 more rows