Export masks for NSE-only constructs ., J, patterns and measure (#6125)

* masking function

* Update data.table.R

* Removed mask for pattern and measure

* exporting pattern and measure

* added news entry

* editing news item

* updating news

* updating news item

* updated news item

* Update NEWS.md

* Update NEWS.md

* updating news

* delete comment

* updated test and mask for J

* improved the error message

* updated error messages

* improving error message

* Update NEWS.md

Co-authored-by: Michael Chirico <michaelchirico4@gmail.com>

* small changes

* Update vignettes/datatable-importing.Rmd

Co-authored-by: Michael Chirico <michaelchirico4@gmail.com>

* Update NEWS.md

Co-authored-by: Michael Chirico <michaelchirico4@gmail.com>

* grammar

* updating error message

* updating example

---------

Co-authored-by: nitish jha <nitishjha@nitishs-MacBook-Air.local>
Co-authored-by: Michael Chirico <michaelchirico4@gmail.com>

Author: 3 people

NAMESPACE

@@ -27,7 +27,7 @@ export(tstrsplit)
 export(frank)
 export(frankv)
 export(address)
-export(.SD,.N,.I,.GRP,.NGRP,.BY,.EACHI)
+export(.SD,.N,.I,.GRP,.NGRP,.BY,.EACHI, ., J, measure, patterns)
 export(rleid)
 export(rleidv)
 export(rowid)

NEWS.md

@@ -100,6 +100,8 @@
 
 16. `print.data.table` gains new argument `show.indices` and option `datatable.show.indices` that allows the user to print a `data.table`'s indices as columns without having to modify the `data.table` itself. Thanks @MichaelChirico for the report and @joshhwuu for the PR.
 
+17. `.`, `J`, `measure`, and `patterns` are now exported for use within `[` and `melt()`, for consistency with other NSE exports like `.N` and `:=`, [#5604](https://github.com/Rdatatable/data.table/issues/5604). Package developers can now import these names to avoid `R CMD check` `NOTE`s about them being undefined variables. Thanks to @MichaelChirico and @ylelkes for the suggestions and @Nj221102 for implementing.
+
 ## TRANSLATIONS
 
 1. Fix a typo in a Mandarin translation of an error message that was hiding the actual error message, [#6172](https://github.com/Rdatatable/data.table/issues/6172). Thanks @trafficfan for the report and @MichaelChirico for the fix.

R/data.table.R

@@ -2770,6 +2770,14 @@ address = function(x) .Call(Caddress, eval(substitute(x), parent.frame()))
   stopf('Check that is.data.table(DT) == TRUE. Otherwise, :=, `:=`(...) and let(...) are defined for use in j, once only and in particular ways. See help(":=").')
 }
 
+J = function(...) {
+  stopf("J() called outside of [.data.table. J() is only intended for use in i.")
+}
+
+. = function(...) {
+  stopf(".() called outside of [.data.table. .() is only intended as an alias for list() inside DT[...].")
+}
+
 let = function(...) `:=`(...)
 
 setDF = function(x, rownames=NULL) {

inst/tests/tests.Rraw

@@ -2186,7 +2186,7 @@ if (ncol(DT)==2L) setnames(DT,c("A","B")) # else don't stop under torture with s
 test(714, DT[,z:=6:10], data.table(A=1:5,B=5,z=6:10))
 
 # Test J alias is now removed outside DT[...] from v1.8.7 (to resolve rJava::J conflict)
-test(715, J(a=1:3,b=4), error=base_messages$missing_function("J"))
+test(715, J(a=1:3,b=4), error="J() called outside of [.data.table. J() is only intended for use in i.")
 
 # Test get in j
 DT = data.table(a=1:3,b=4:6)

vignettes/datatable-importing.Rmd

@@ -118,7 +118,7 @@ aggr = function (x) {
 }
 ```
 
-The case for `data.table`'s special symbols (`.SD`, `.BY`, `.N`, `.I`, `.GRP`, `.NGRP`, and `.EACHI`; see `?.N`) and assignment operator (`:=`) is slightly different. You should import whichever of these values you use from `data.table`'s namespace to protect against any issues arising from the unlikely scenario that we change the exported value of these in the future, e.g. if you want to use `.N`, `.I`, and `:=`, a minimal `NAMESPACE` would have:
+The case for `data.table`'s special symbols (e.g. `.SD` and `.N`) and assignment operator (`:=`) is slightly different (see `?.N` for more, including a complete listing of such symbols). You should import whichever of these values you use from `data.table`'s namespace to protect against any issues arising from the unlikely scenario that we change the exported value of these in the future, e.g. if you want to use `.N`, `.I`, and `:=`, a minimal `NAMESPACE` would have:
 
 ```r
 importFrom(data.table, .N, .I, ':=')