:= operator does not suppress print in rmarkdown and quarto

[ntthung]

I've been using this package for several years and never had this issue until now.

In rmarkdown, the := doesn't suppress print. This doesn't happen in the console, only in rmarkdown.

```{r}
library(data.table)
DT <- data.table(x = 1:2, y = 1:2)
DT[, z := 1:2]
# this prints although it shouldn't

May relate to this: rstudio/rmarkdown#829, but this is now with both the dev and stable versions of rmarkdown. I've tried updating both data.table and rmarkdown but the issue persists.

sessionInfo()

R version 4.5.3 (2026-03-11 ucrt)
Platform: x86_64-w64-mingw32/x64
Running under: Windows 11 x64 (build 26100)

Matrix products: default
LAPACK version 3.12.1

locale:
[1] LC_COLLATE=English_United States.utf8
[2] LC_CTYPE=English_United States.utf8
[3] LC_MONETARY=English_United States.utf8
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.utf8

time zone: America/Chicago
tzcode source: internal

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

other attached packages:
[1] ggplot2_4.0.2 data.table_1.18.99

loaded via a namespace (and not attached):
[1] vctrs_0.7.1 cli_3.6.5 knitr_1.51
[4] rlang_1.1.7 xfun_0.56 otel_0.2.0
[7] generics_0.1.4 S7_0.2.1 glue_1.8.0
[10] htmltools_0.5.9 rmarkdown_2.30.3 scales_1.4.0
[13] grid_4.5.3 evaluate_1.0.5 tibble_3.3.1
[16] fastmap_1.2.0 yaml_2.3.12 lifecycle_1.0.5
[19] compiler_4.5.3 dplyr_1.2.0 RColorBrewer_1.1-3
[22] pkgconfig_2.0.3 rstudioapi_0.18.0 digest_0.6.39
[25] farver_2.1.2 R6_2.6.1 tidyselect_1.2.1
[28] pillar_1.11.1 magrittr_2.0.4 tools_4.5.3
[31] withr_3.0.2 gtable_0.3.6

[aitap]

Thanks for the report! I couldn't reproduce the problem. Could you please provide more details? If I put your code, including the terminating ```, into foo.Rmd, and then call rmarkdown::render("foo.Rmd"), then the result of DT[, z := 1:2] is not auto-printed for me. If you're using RStudio notebook mode, this could be the same problem as yihui/knitr#2427, although so far nobody reported where does the extra print() come from.

[ntthung]

Thank you! Yes I am using it in notebook mode. This only occurs in the editor, not when rendering. I checked the rmarkdown repo and found the old issue but didn't think to check the knitr repo. It is exactly as reported in the knitr issue.