library(data.table)
library(dtplyr)
library(dplyr, warn.conflicts = FALSE)

# Simple sample data
dt <- data.table(a = 1:5, b = 6:10)
immutable <- lazy_dt(dt)
mutable <- lazy_dt(dt, immutable = FALSE)

# mutate() works as expected
immutable %>% mutate(c = a + b) %>% show_query()
#> copy(`_DT1`)[, `:=`(c = a + b)]
mutable %>% mutate(c = a + b) %>% show_query()
#> `_DT2`[, `:=`(c = a + b)]

# relocate() works as expected
immutable %>% relocate(b) %>% show_query()
#> setcolorder(copy(`_DT1`), c("b", "a"))
mutable %>% relocate(b) %>% show_query()
#> setcolorder(`_DT2`, c("b", "a"))

# rename() triggers copy
immutable %>% rename(A = a, B = b) %>% show_query()
#> setnames(copy(`_DT1`), c("a", "b"), c("A", "B"))
mutable %>% rename(A = a, B = b) %>% show_query()
#> setnames(copy(`_DT2`), c("a", "b"), c("A", "B"))

# rename_with() triggers copy
immutable %>% rename_with(toupper) %>% show_query()
#> setnames(copy(`_DT1`), toupper)
mutable %>% rename_with(toupper) %>% show_query()
#> setnames(copy(`_DT2`), toupper)