library(tidyverse)
library(dtplyr)

data_df <- tribble(
  ~group, ~date, ~value,
  "a", "2021-01-01", 1,
  "a", "2021-01-02", 2,
  "b", "2021-01-02", 2
)

data_df %>%
  complete(nesting(group), date = "2021-01-01")
#> # A tibble: 4 x 3
#>   group date       value
#>   <chr> <chr>      <dbl>
#> 1 a     2021-01-01     1
#> 2 b     2021-01-01    NA
#> 3 a     2021-01-02     2
#> 4 b     2021-01-02     2

data_df %>%
  lazy_dt() %>%
  complete(nesting(group), date = "2021-01-01") %>%
  as_tibble()
#> Error: `by` can't contain join column `V1` which is missing from RHS.

sessionInfo()
#> R version 4.0.4 (2021-02-15)
#> Platform: x86_64-apple-darwin17.0 (64-bit)
#> Running under: macOS Big Sur 10.16
#> 
#> Matrix products: default
#> BLAS:   /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRblas.dylib
#> LAPACK: /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRlapack.dylib
#> 
#> locale:
#> [1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#>  [1] dtplyr_1.1.0.9000 forcats_0.5.1     stringr_1.4.0     dplyr_1.0.5      
#>  [5] purrr_0.3.4.9000  readr_1.4.0       tidyr_1.1.3       tibble_3.1.1     
#>  [9] ggplot2_3.3.3     tidyverse_1.3.1  
#> 
#> loaded via a namespace (and not attached):
#>  [1] styler_1.4.1      tidyselect_1.1.0  xfun_0.22         haven_2.4.1      
#>  [5] colorspace_2.0-0  vctrs_0.3.7       generics_0.1.0    htmltools_0.5.1.1
#>  [9] yaml_2.2.1        utf8_1.2.1        rlang_0.4.10      pillar_1.6.0     
#> [13] glue_1.4.2        withr_2.4.2       DBI_1.1.1         dbplyr_2.1.1     
#> [17] modelr_0.1.8      readxl_1.3.1      lifecycle_1.0.0   munsell_0.5.0    
#> [21] gtable_0.3.0      cellranger_1.1.0  rvest_1.0.0       evaluate_0.14    
#> [25] knitr_1.33        fansi_0.4.2       highr_0.9         broom_0.7.6      
#> [29] Rcpp_1.0.6        backports_1.2.1   scales_1.1.1      jsonlite_1.7.2   
#> [33] fs_1.5.0          hms_1.0.0         digest_0.6.27     stringi_1.5.3    
#> [37] grid_4.0.4        cli_2.4.0         tools_4.0.4       magrittr_2.0.1   
#> [41] crayon_1.4.1      pkgconfig_2.0.3   ellipsis_0.3.1    data.table_1.14.0
#> [45] xml2_1.3.2        reprex_2.0.0      lubridate_1.7.10  rstudioapi_0.13  
#> [49] assertthat_0.2.1  rmarkdown_2.7     httr_1.4.2        R6_2.5.0         
#> [53] compiler_4.0.4