Unnesting tibble with zero rows removes unnested column

Here is an example that produces the problem:

df <- tibble(
 a = list(c(1, 2), 3),
 b = c(4,5)
)

df %>%
  unnest(a) %>%
  colnames
# [1] "b" "a"

df %>%
  filter(b==1) %>%
  unnest(a) %>%
  colnames
# [1] "b"

If the special case occurs that the tibble being unnested has no rows, all code acting on the unnested column breaks.

Thanks, confirmed with both the CRAN version and 581c2c0.

I'll try this.

Closes tidyverse#483

A bit more of a reprex to help me understand the problem:

library(tidyr)

df <- tibble::tibble(a = list(1), y = 1)
df %>% unnest(a) %>% str()
#> Classes 'tbl_df', 'tbl' and 'data.frame':    1 obs. of  2 variables:
#>  $ y: num 1
#>  $ a: num 1
df %>% .[0, ] %>% unnest(a) %>% str()
#> Classes 'tbl_df', 'tbl' and 'data.frame':    0 obs. of  1 variable:
#>  $ y: num

^{Created on 2019-01-22 by the reprex package (v0.2.1.9000)}

I think the root cause is actually this:

list_col_type(character())
#> [1] "data.frame"

Preserve empty columns when unnesting (tidyverse#535)

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Unnesting tibble with zero rows removes unnested column #483

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Unnesting tibble with zero rows removes unnested column #483

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krlmlr commented on Sep 13, 2018

hadley commented on Jan 4, 2019

frederikziebell commented on Jan 4, 2019

hadley commented on Jan 4, 2019

khailper commented on Jan 19, 2019

hadley commented on Jan 22, 2019

hadley commented on Jan 22, 2019

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