DT[FALSE, a:=1L] no longer prints, closes #887.

R/data.table.R

@@ -634,8 +634,10 @@ chmatch2 <- function(x, table, nomatch=NA_integer_) {
  if (is.null(jsub)) return(NULL)
 
  if (is.call(jsub) && jsub[[1L]]==as.name(":=")) {
- if (identical(irows, integer())) # short circuit do-nothing, don't do further checks on .SDcols for example
+ if (identical(irows, integer())) { # short circuit do-nothing, don't do further checks on .SDcols for example
+ .global$print = address(x)
  return(invisible(x)) # irows=NULL means all rows at this stage
+ }
  if (!with) {
  if (is.null(names(jsub)) && is.name(jsub[[2L]])) {
  # TO DO: uncomment these warnings in next release. Later, make both errors.

README.md

@@ -15,45 +15,47 @@
 
 #### BUG FIXES
 
- 1. `if (TRUE) DT[,LHS:=RHS]` now doesn't print (thanks to Jureiss, [#869](https://github.com/Rdatatable/data.table/issues/869)). Test added. To get this to work we've had to live with one downside: if a `:=` is used inside a function with no `DT[]` before the end of the function, then the next time `DT` is typed at the prompt, nothing will be printed. A repeated `DT` will print. To avoid this: include a `DT[]` after the last `:=` in your function. If that is not possible (e.g., it's not a function you can change) then `print(DT)` and `DT[]` at the prompt are guaranteed to print. As before, adding an extra `[]` on the end of `:=` query is a recommended idiom to update and then print; e.g. `> DT[,foo:=3L][]`
+ 1. `if (TRUE) DT[,LHS:=RHS]` no longer prints, [#869](https://github.com/Rdatatable/data.table/issues/869). Tests added. To get this to work we've had to live with one downside: if a `:=` is used inside a function with no `DT[]` before the end of the function, then the next time `DT` is typed at the prompt, nothing will be printed. A repeated `DT` will print. To avoid this: include a `DT[]` after the last `:=` in your function. If that is not possible (e.g., it's not a function you can change) then `print(DT)` and `DT[]` at the prompt are guaranteed to print. As before, adding an extra `[]` on the end of `:=` query is a recommended idiom to update and then print; e.g. `> DT[,foo:=3L][]`. Thanks to Jureiss for reporting.
 
- 2. `:=` no longer prints in knitr for consistency with behaviour at the prompt, [#505](https://github.com/Rdatatable/data.table/issues/505). Output of a test `knit("knitr.Rmd")` is now in data.table's unit tests.
+ 2. `DT[FALSE,LHS:=RHS]` no longer prints either, [#887](https://github.com/Rdatatable/data.table/issues/887). Thanks to Jureiss for reporting.
 
- 3. `knitr::kable()` works again without needing to upgrade from knitr v1.6 to v1.7. Packages which evaluate user code and don't wish to import data.table need to be added to `data.table:::cedta.pkgEvalsUserCode` and now only the `eval` part is made data.table-aware (the rest of such package's code is left data.table-unaware). `data.table:::cedta.override` is now empty and will be deprecated if no need for it arises.
+ 3. `:=` no longer prints in knitr for consistency with behaviour at the prompt, [#505](https://github.com/Rdatatable/data.table/issues/505). Output of a test `knit("knitr.Rmd")` is now in data.table's unit tests. Thanks to Corone for the illustrated report.
+
+ 4. `knitr::kable()` works again without needing to upgrade from knitr v1.6 to v1.7, [#809](https://github.com/Rdatatable/data.table/issues/809). Packages which evaluate user code and don't wish to import data.table need to be added to `data.table:::cedta.pkgEvalsUserCode` and now only the `eval` part is made data.table-aware (the rest of such package's code is left data.table-unaware). `data.table:::cedta.override` is now empty and will be deprecated if no need for it arises. Thanks to badbye and Stephanie Locke for reporting.
 
- 4. `as.data.table.list` with list input having 0-length items, e.g. `x = list(a=integer(0), b=3:4)`. `as.data.table(x)` recycles item `a` with `NA`s to fit the length of the longer column `b` (length=2), as before now, but with an additional warning message that the item has been recycled with `NA`. Closes [#847](https://github.com/Rdatatable/data.table/issues/847). Thanks to @tvinodr for the report. This was a regression from 1.9.2.
+ 5. `as.data.table.list` with list input having 0-length items, e.g. `x = list(a=integer(0), b=3:4)`. `as.data.table(x)` recycles item `a` with `NA`s to fit the length of the longer column `b` (length=2), as before now, but with an additional warning message that the item has been recycled with `NA`. Closes [#847](https://github.com/Rdatatable/data.table/issues/847). Thanks to @tvinodr for the report. This was a regression from 1.9.2.
 
- 5. `DT[i, j]` when `i` returns all `FALSE` and `j` contains some length-0 values (ex: `integer(0)`) now returns an empty data.table as it should. Closes [#758](https://github.com/Rdatatable/data.table/issues/758) and [#813](https://github.com/Rdatatable/data.table/issues/813). Thanks to @tunaaa and @nigmastar for the nice reproducible reports. 
+ 6. `DT[i, j]` when `i` returns all `FALSE` and `j` contains some length-0 values (ex: `integer(0)`) now returns an empty data.table as it should. Closes [#758](https://github.com/Rdatatable/data.table/issues/758) and [#813](https://github.com/Rdatatable/data.table/issues/813). Thanks to @tunaaa and @nigmastar for the nice reproducible reports. 
 
- 6. `allow.cartesian` is ignored during joins when: 
+ 7. `allow.cartesian` is ignored during joins when: 
  * `i` has no duplicates and `mult="all"`. Closes [#742](https://github.com/Rdatatable/data.table/issues/742). Thanks to @nigmastar for the report. 
  * assigning by reference, i.e., `j` has `:=`. Closes [#800](https://github.com/Rdatatable/data.table/issues/800). Thanks to @matthieugomez for the report.
 
  In both these cases (and during a `not-join` which was already fixed in [1.9.4](https://github.com/Rdatatable/data.table/blob/master/README.md#bug-fixes-1)), `allow.cartesian` can be safely ignored.
 
- 7. `names<-.data.table` works as intended on data.table unaware packages with Rv3.1.0+. Closes [#476](https://github.com/Rdatatable/data.table/issues/476) and [#825](https://github.com/Rdatatable/data.table/issues/825). Thanks to ezbentley for reporting [here](http://stackoverflow.com/q/23256177/559784) on SO and to @narrenfrei.
+ 8. `names<-.data.table` works as intended on data.table unaware packages with Rv3.1.0+. Closes [#476](https://github.com/Rdatatable/data.table/issues/476) and [#825](https://github.com/Rdatatable/data.table/issues/825). Thanks to ezbentley for reporting [here](http://stackoverflow.com/q/23256177/559784) on SO and to @narrenfrei.
 
- 8. `.EACHI` is now an exported symbol (just like `.SD`,`.N`,`.I`,`.GRP` and `.BY` already were) so that packages using `data.table` and `.EACHI` pass `R CMD check` with no NOTE that this symbol is undefined. Thanks to Matt Bannert for highlighting.
+ 9. `.EACHI` is now an exported symbol (just like `.SD`,`.N`,`.I`,`.GRP` and `.BY` already were) so that packages using `data.table` and `.EACHI` pass `R CMD check` with no NOTE that this symbol is undefined. Thanks to Matt Bannert for highlighting.
 
- 9. `DT[colA == max(colA)]` now works again without needing `options(datatable.auto.index=FALSE)`. Thanks to Jan Gorecki and kaybenleroll, [#858](https://github.com/Rdatatable/data.table/issues/858). Test added.
+ 10. `DT[colA == max(colA)]` now works again without needing `options(datatable.auto.index=FALSE)`. Thanks to Jan Gorecki and kaybenleroll, [#858](https://github.com/Rdatatable/data.table/issues/858). Test added.
 
- 10. `DT[colA %in% c("id1","id2","id2","id3")]` now ignores the RHS duplicates (as before, consistent with base R) without needing `options(datatable.auto.index=FALSE)`. Thanks to Dayne Filer for reporting.
+ 11. `DT[colA %in% c("id1","id2","id2","id3")]` now ignores the RHS duplicates (as before, consistent with base R) without needing `options(datatable.auto.index=FALSE)`. Thanks to Dayne Filer for reporting.
 
- 11. If `DT` contains a column `class` (happens to be a reserved attribute name in R) then `DT[class=='a']` now works again without needing `options(datatable.auto.index=FALSE)`. Thanks to sunnyghkm for reporting, [#871](https://github.com/Rdatatable/data.table/issues/871).
+ 12. If `DT` contains a column `class` (happens to be a reserved attribute name in R) then `DT[class=='a']` now works again without needing `options(datatable.auto.index=FALSE)`. Thanks to sunnyghkm for reporting, [#871](https://github.com/Rdatatable/data.table/issues/871).
 
- 12. Some optimisations of `.SD` in `j` was done in 1.9.4, refer to [#735](https://github.com/Rdatatable/data.table/issues/735). Due to an oversight, j-expressions of the form c(lapply(.SD, ...), list(...)) were optimised improperly. This is now fixed. Thanks to @mmeierer for filing [#861](https://github.com/Rdatatable/data.table/issues/861).
+ 13. Some optimisations of `.SD` in `j` was done in 1.9.4, refer to [#735](https://github.com/Rdatatable/data.table/issues/735). Due to an oversight, j-expressions of the form c(lapply(.SD, ...), list(...)) were optimised improperly. This is now fixed. Thanks to @mmeierer for filing [#861](https://github.com/Rdatatable/data.table/issues/861).
 
- 13. `j`-expressions in `DT[, col := x$y()]` (or) `DT[, col := x[[1]]()]` are now (re)constructed properly. Thanks to @ihaddad-md for reporting. Closes [#774](https://github.com/Rdatatable/data.table/issues/774).
+ 14. `j`-expressions in `DT[, col := x$y()]` (or) `DT[, col := x[[1]]()]` are now (re)constructed properly. Thanks to @ihaddad-md for reporting. Closes [#774](https://github.com/Rdatatable/data.table/issues/774).
 
- 14. `format.ITime` now handles negative values properly. Closes [#811](https://github.com/Rdatatable/data.table/issues/811). Thanks to @StefanFritsch for the report along with the fix!
+ 15. `format.ITime` now handles negative values properly. Closes [#811](https://github.com/Rdatatable/data.table/issues/811). Thanks to @StefanFritsch for the report along with the fix!
 
- 15. Compatibility with big endian machines (e.g., SPARC and PowerPC) is restored. Most Windows, Linux and Mac systems are little endian; type `.Platform$endian` to confirm. Thanks to Gerhard Nachtmann for reporting and the [QEMU project](http://qemu.org/) for their PowerPC emulator.
+ 16. Compatibility with big endian machines (e.g., SPARC and PowerPC) is restored. Most Windows, Linux and Mac systems are little endian; type `.Platform$endian` to confirm. Thanks to Gerhard Nachtmann for reporting and the [QEMU project](http://qemu.org/) for their PowerPC emulator.
 
- 16. `DT[, LHS := RHS]` with RHS is of the form `eval(parse(text = foo[1]))` referring to columns in `DT` is now handled properly. Closes [#880](https://github.com/Rdatatable/data.table/issues/880). Thanks to tyner.
+ 17. `DT[, LHS := RHS]` with RHS is of the form `eval(parse(text = foo[1]))` referring to columns in `DT` is now handled properly. Closes [#880](https://github.com/Rdatatable/data.table/issues/880). Thanks to tyner.
 
- 17. `subset` handles extracting duplicate columns in consistency with data.table's rule - if a column name is duplicated, then accessing that column using column number should return that column, whereas accessing by column name (due to ambiguity) will always extract the first column. Closes [#891](https://github.com/Rdatatable/data.table/issues/891). Thanks to @jjzz.
+ 18. `subset` handles extracting duplicate columns in consistency with data.table's rule - if a column name is duplicated, then accessing that column using column number should return that column, whereas accessing by column name (due to ambiguity) will always extract the first column. Closes [#891](https://github.com/Rdatatable/data.table/issues/891). Thanks to @jjzz.
 
- 18. `rbindlist` handles combining levels of data.tables with both ordered and unordered factor columns properly. Closes [#899](https://github.com/Rdatatable/data.table/issues/899). Thanks to @ChristK.
+ 19. `rbindlist` handles combining levels of data.tables with both ordered and unordered factor columns properly. Closes [#899](https://github.com/Rdatatable/data.table/issues/899). Thanks to @ChristK.
 
 #### NOTES
 

tests/autoprint.R

@@ -6,6 +6,10 @@ DT # yes
 DT[1] # yes
 DT[2,a:=3L] # no
 DT # yes
+DT[FALSE,a:=3L] # no
+DT[a==4L,a:=5L] # no
+DT[a %in% 4:8, a:=5L] # no
+DT # yes
 print(DT[2,a:=4L]) # yes
 print(DT) # yes
 if (TRUE) DT[2,a:=5L] # no. used to print before v1.9.5

tests/autoprint.Rout.save

@@ -32,6 +32,13 @@ Loading required package: data.table
  a
 1: 1
 2: 3
+> DT[FALSE,a:=3L] # no
+> DT[a==4L,a:=5L] # no
+> DT[a %in% 4:8, a:=5L] # no
+> DT # yes
+ a
+1: 1
+2: 3
 > print(DT[2,a:=4L]) # yes
  a
 1: 1