What does sp_restore_filelistonly do? In SQL Server 2017, after applying Cumulative Update 7, there's a new system stored procedure in master called sp_restore_filelistonly. What's it for?
sp_restore_filelistonly is a (currently) undocumented stored procedure with two parameters:


@device_type NVARCHAR(10) - like 'DISK'
@backup_path NVARCHAR(360) - which needs to point to the exact backup file you want to example, not just the folder path where it lives


When you point it at a backup file, like this:

EXEC sp_restore_filelistonly
    @device_type = 'DISK',
    @backup_path = 'E:\MSSQL2017\Backup\StackOverflow2010.bak';


It functions like RESTORE FILELISTONLY:

RESTORE FILELISTONLY FROM DISK = 'E:\MSSQL2017\Backup\StackOverflow2010.bak' WITH FILE = 1;


You get an output set with the files included in the backup:




LogicalName
PhysicalName
Type (D for full, L for log, etc)
FileGroupName
Size (in bytes)
MaxSize
FileId
CreateLSN
DropLSN
UniqueID
ReadOnlyLSN
ReadWriteLSN
BackupSizeInBytes - note that this is the uncompressed size, so if your backup used compression, you won't see the real file size here
SourceBlockSize
FileGroupId
LogGroupGUID
DifferentialBaseLSN
DifferentialBaseGUID
IsReadOnly
IsPresent
TDEThumbprint
SnapshotUrl


Why would Microsoft build it? Well, if they want to let someone get a file list without running a RESTORE command. Could be a separation-of-duties thing, or could be making the automation plumbing easier for Azure Managed Instances.