Get prints Null as NA by default

[nzxwang]

Get currently calls GetAttribute with its default nullAsNa = TRUE. This leads to problems when the user is trying to Prune or otherwise traverse the tree using is.na().

data.tree/R/node_methods_traversal.R

Line 190 in 24bd7da

function(x) GetAttribute(x,

Reprex:

> library(data.tree)
> data(acme)
> acme$Get("cost")
               Acme Inc.               Accounting             New Software 
                      NA                       NA                  1000000 
New Accounting Standards                 Research         New Product Line 
                  500000                       NA                  2000000 
                New Labs                       IT                Outsource 
                  750000                       NA                   400000 
                Go agile              Switch to R 
                  250000                    50000 
> Prune(acme, function(node) is.na(node$cost))
Error in if (!pruneFun(node$children[[i]])) { : 
  argument is of length zero
> #This will work
>Prune(acme, function(node) is.null(node$cost))
[1] 7

Understandably, setting nullAsNa = FALSE returns a list instead of a vector,

> class(acme$Get("cost", nullAsNa=FALSE))
[1] "list"
> class(acme$Get("cost", nullAsNa=TRUE))
[1] "numeric"

Still, should this print a warning or be documented somewhere to avoid confusion?

[gluc]

Thx for this. Yeah, that's a bit of an ugly sucker. Warning would be annoying for many of the things I'm using. But if you have a good idea how to document, then I would very much welcome a PR. Thx!

[nzxwang]

Perhaps I'm being naive, but it seems like this problem would only occur in the evaluation of this line

data.tree/R/node_methods_sideeffect.R

Line 117 in 24bd7da

if ( !pruneFun(node$children[[i]]) ) {

What if instead of just checking ! of pruneFun(node$children[[i]]) which gives the arcane error upon it evaluating to logical(0), also check for is.null in which case print an error or warning with additional information for the user to read nullAsNa in GetAttribute's help?