Expand tibble of email dataset in R - r

Question

I have a massive tibble of my email data which looks like the following:
library(dplyr)
emails <- tibble(
from = c('employee.1#xtra.co','employee.5#xtra.co','employee.1#xtra.co',
'employee.3#xtra.co','employee.1#xtra.co'),
to = list(
c('employee.5#xtra.co', 'employee.3xtra.co'),
c('employee.3#xtra.co', 'employee.1#xtra.co'),
c('employee.2#xtra.co'),
c('employee.1#xtra.co'),
c('employee.3#xtra.co','employee.5#xtra.co','employee.6#xtra.co')),
cc = list(
c('employee.2xtra.co', 'employee.4xtra.co', 'employee.6xtra.co'),
c('employee.1xtra.co', 'employee.8xtra.co', 'employee.6xtra.co'),
NA,
c('employee.2xtra.co', 'employee.4xtra.co'),
c('employee.2xtra.co', 'employee.6xtra.co'))
)
emails
# A tibble: 5 x 3
from to cc
<chr> <list> <list>
1 employee.1#xtra.co <chr [2]> <chr [3]>
2 employee.5#xtra.co <chr [2]> <chr [3]>
3 employee.1#xtra.co <chr [1]> <lgl [1]>
4 employee.3#xtra.co <chr [1]> <chr [2]>
5 employee.1#xtra.co <chr [3]> <chr [2]>
I need your help to be able to expand each record for each combination. For example, what I want to achieve for row 1 is:
from to cc
employee.1#xtra.co employee.5#xtra.co employee.2xtra.co
employee.1#xtra.co employee.5#xtra.co employee.4xtra.co
employee.1#xtra.co employee.5#xtra.co employee.6xtra.co
employee.1#xtra.co employee.3xtra.co employee.2xtra.co
employee.1#xtra.co employee.3xtra.co employee.4xtra.co
employee.1#xtra.co employee.3xtra.co employee.6xtra.co
Thank you very much for your time.

Answer 1

We can apply unnest twice.
library(dplyr)
library(tidyr)
emails2 <- emails %>%
unnest(cols = "to") %>%
unnest(cols = "cc")
head(emails2)
# # A tibble: 6 x 3
# from to cc
# <chr> <chr> <chr>
# 1 employee.1#xtra.co employee.5#xtra.co employee.2xtra.co
# 2 employee.1#xtra.co employee.5#xtra.co employee.4xtra.co
# 3 employee.1#xtra.co employee.5#xtra.co employee.6xtra.co
# 4 employee.1#xtra.co employee.3xtra.co employee.2xtra.co
# 5 employee.1#xtra.co employee.3xtra.co employee.4xtra.co
# 6 employee.1#xtra.co employee.3xtra.co employee.6xtra.co
If you have more than two columns to expand, below is one approach. First identify the columns that are list. Store the column names in names_target, and then use a for loop to repeatedly apply the unnest function.
names_target <- emails %>%
select(where(is.list)) %>%
names()
temp <- emails
for (i in names_target){
temp <- temp %>% unnest(cols = all_of(i))
}
identical(temp, emails2)
# [1] TRUE