persistent .internal.selfref

[AmitaiPerlstein]

R 3.2.3
Can't get rid of Warning message:
In [.data.table(table, , :=("min.in.day", 60 * hour(table$date.time) + :
Invalid .internal.selfref detected and fixed by taking a (shallow) copy of the data.table so that := can add this new column by reference. At an earlier point, this data.table has been copied by R (or been created manually using structure() or similar). Avoid key<-, names<- and attr<- which in R currently (and oddly) may copy the whole data.table. Use set* syntax instead to avoid copying: ?set, ?setnames and ?setattr.

Matt Dowle supposedly referred to the issue in:
http://stackoverflow.com/questions/20687235/warning-invalid-internal-selfref-detected-when-adding-a-column-to-a-data-tab
but the problem is NOT reproduced in
DT <- data.table(x=1:2) # name the object 'DT'
DT.l <- list(DT=DT) # create a list containing one data.table
y <- DT.l$DT # get back the data.table
y[, bla := 1L] # now add by reference

works fine but warning message will occur

The notorious warning is NOT raised

[KillariDev]

I am facing the same issue here is a minimum working example:

library(data.table)
dt <- data.table(resp=c(1,2,3,4,5))
wide <- copy(list(metrics = dt))$metrics
wide[, id___ := .I]

Warning I get is:
"
Warning message:
In [.data.table(wide, , :=(id___, .I)) :
Invalid .internal.selfref detected and fixed by taking a (shallow) copy of the data.table so that := can add this new column by reference. At an earlier point, this data.table has been copied by R (or been created manually using structure() or similar). Avoid key<-, names<- and attr<- which in R currently (and oddly) may copy the whole data.table. Use set* syntax instead to avoid copying: ?set, ?setnames and ?setattr. Also, in R<=v3.0.2, list(DT1,DT2) copied the entire DT1 and DT2 (R's list() used to copy named objects); please upgrade to R>v3.0.2 if that is biting. If this message doesn't help, please report to datatable-help so the root cause can be fixed.
"
sessionInfo()
R version 3.2.3 (2015-12-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=Finnish_Finland.1252 LC_CTYPE=Finnish_Finland.1252 LC_MONETARY=Finnish_Finland.1252
[4] LC_NUMERIC=C LC_TIME=Finnish_Finland.1252

attached base packages:
[1] stats graphics grDevices datasets utils methods base

other attached packages:
[1] data.table_1.9.6

loaded via a namespace (and not attached):
[1] tools_3.2.3 chron_2.3-47