The IDL struct singleWriteResult is used to help share code for all different types of writes (insert, update, delete, etc). It will need to be updated to optionally include cursor metrics:

structs: 
  singleWriteResult: 
    # ...
    fields: 
      # ...
        cursorMetrics: 
          type: CursorMetrics
          optional: true
          description: "cursor metrics if requested for this write"

The command layer class CmdUpdate provides callbacks to code common to different types of writes. We can ensure that we add cursor metrics as requested using the singleWriteHandler and postProcessHandler, similar to what is currently done for upsertInfo.

The performUpdates() function provides a place where we can check to see if we need to add cursor metrics to the SingleWriteResult, if requested on the UpdateOpEntry. The write place to do this is after finishCurOp() is called, when the relevant metrics are created.