Drupal 8 Migrate Plus - CSV Row Number as key In the Drupal 7 migrate module, you can use 'csvrownum' as the mapping key when migrating content from a CSV (https://www.drupal.org/node/1152158). For the Drupal 8 version, I am not sure what the equivalent is. Here is my yml file configuration (migrate plus):

id: timesheet_data
label: Importing Timesheet
migration_group: csvimport
migration_tags:
  - node
  - csvimport
source:
  plugin: csv
  path: 'somepath/timesheet.csv'
  header_row_count: 1
  keys:
    - csvrownum
  column_names:
    0:
      name: Name of Contact
    1:
      address: Address
destination:
  plugin: 'entity:node'
  default_bundle: timesheets
process:
  title: name


I tried this approach thinking it might be similar to the drupal 7 migrate module. I also tried not specifying  a key, both resulted in an error.
I couldn't find a way to do this, but I found out you can specify multiple keys to make the row more unique for mapping. 

keys:
- name
- address


When I applied more keys as a mapping, all the records imported since it was more unique. 

Hopefully this helps someone else.