Bug: distinct() ignores groups

[mgirlich]

library(dplyr)
library(dbplyr)

memdb_frame(x = 1:2, y = 1) %>% 
  group_by(x) %>% 
  distinct(y)
#> # Source:   lazy query [?? x 2]
#> # Database: sqlite 3.33.0 [:memory:]
#> # Groups:   x
#>       y
#>   <dbl>
#> 1     1

tibble(x = 1:2, y = 1) %>% 
  group_by(x) %>% 
  distinct(y)
#> # A tibble: 2 x 2
#> # Groups:   x [2]
#>       x     y
#>   <int> <dbl>
#> 1     1     1
#> 2     2     1

^{Created on 2020-11-10 by the reprex package (v0.3.0)}

Session info

devtools::session_info()
#> ─ Session info ───────────────────────────────────────────────────────────────
#>  setting  value                       
#>  version  R version 4.0.2 (2020-06-22)
#>  os       macOS Catalina 10.15.7      
#>  system   x86_64, darwin17.0          
#>  ui       X11                         
#>  language (EN)                        
#>  collate  en_US.UTF-8                 
#>  ctype    en_US.UTF-8                 
#>  tz       UTC                         
#>  date     2020-11-10                  
#> 
#> ─ Packages ───────────────────────────────────────────────────────────────────
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#> [1] /Library/Frameworks/R.framework/Versions/4.0/Resources/library

[hadley]

Do you want to have a go at fixing this? The correct behaviour of distinct() falls out of my brain very quickly/easily.