as_tibble_row() doesn't work with date vectors

[FrancoisR95]

In tibble 3.0.1, as_tibble_row(x) returns an error when x is a vector of dates.

The expected behavior would be to return a tibble row containing dates, exactly like as_tibble_col() or tibble() are doing.

1. Example of the issue with as_tibble_row:

      x <- c(col1 = as.Date("2012-04-04"), col2 = as.Date("2012-05-04"))
      as_tibble_row(x)

This returns the following error:

Error: `x` must be a bare vector in `as_tibble_row()`, not Date.

2. On the contrary, the same code is working fine with as_tibble_col:

      x <- c(col1 = as.Date("2012-04-04"), col2 = as.Date("2012-05-04"))
      as_tibble_col(x)

Result:

# A tibble: 2 x 1
  value     
  <date>    
1 2012-04-04
2 2012-05-04

The same is also obtained with tibble(x) instead of as_tibble_col(x).

3. Also a code for creating a 2-column tibble of dates is handled perfectly by tibble():

tibble(col1 = as.Date("2012-02-12"), col2 = as.Date(as.Date("2012-04-01"):as.Date("2012-04-05"), origin="1970-01-01"))
tibble(x)

Result:

# A tibble: 5 x 2
  col1       col2      
  <date>     <date>    
1 2012-02-12 2012-04-01
2 2012-02-12 2012-04-02
3 2012-02-12 2012-04-03
4 2012-02-12 2012-04-04
5 2012-02-12 2012-04-05

Conclusion
The behavior of as_tibble_row() with date vectors seems to be a bug, or at least is very inconsistent and unexpected. It's also really a pity when the code of the as_tibble_row(x) function (new_tibble(as.list(x), nrow = 1)) would work just fine if there wasn't, in the function, an unfortunate test making this unnecessary error... This test was introduced recently (6f572f5#diff-cb6cd20025e0469d14d1ce6271cbf679) in order to try to fix #739 but the fix is much worse than the problem (which in my opinion was not even a real problem, basically it was said that an error message, which was "All elements must be size one, use list() to wrap.", was not clear enough but I think it was rather clear, and better and clearer at least than now getting this unexpected error "x must be a bare vector in as_tibble_row(), not Date" for something which should work).

[lionel-]

It's also really a pity when the code of the as_tibble_row(x) function (new_tibble(as.list(x), nrow = 1)) would work just fine if there wasn't, in the function, an unfortunate test making this unnecessary error...

new_tibble() is a bare bones function. The implementation you're suggesting creates corrupt tibbles.

To handle arbitrary vectors, vec_chop2() would be useful but it isn't implemented yet.

library(vctrs)
library(rlang)

vec_chop2 <- function(x) {
  stopifnot(
    vec_is(x),
    # Unimplemented:
    !is.data.frame(x),
    is_null(dim(x))
  )

  names <- names(x)
  if (is_null(names)) {
    vec_chop2_unnamed(x)
  } else {
    vec_chop2_named(x, names)
  }
}
vec_chop2_unnamed <- function(x) {
  n <- vec_size(x)
  out <- vector("list", n)

  for (i in seq_len(n)) {
    out[[i]] <- x[[i]]
  }

  out
}
vec_chop2_named <- function(x, names) {
  n <- vec_size(x)
  out <- vector("list", n)
  out_names <- character(n)

  for (i in seq_len(n)) {
    out[[i]] <- x[[i]]
    out_names[[i]] <- names[[i]]
  }

  names(out) <- out_names
  out
}

vec_chop2() has more consistent handling than as.list(), for instance with factors:

fct <- set_names(factor(c("a", "b")), c("foo", "bar"))

as.list(fct)
#> [[1]]
#> foo
#>   a
#> Levels: a b
#>
#> [[2]]
#> bar
#>   b
#> Levels: a b

vec_chop2(fct)
#> $foo
#> [1] a
#> Levels: a b
#>
#> $bar
#> [1] b
#> Levels: a b

date <- c(as.Date("2020-01-01"), as.Date("2020-01-02"))
date <- set_names(date, c("foo", "bar"))

vec_chop2(date)
#> $foo
#> [1] "2020-01-01"
#>
#> $bar
#> [1] "2020-01-02"

as_tibble_row2 <- function(x) {
  if (!vec_is_list(x)) {
    x <- vec_chop2(x)
  }

  tibble::as_tibble_row(x)
}

as_tibble_row2(fct)
#> # A tibble: 1 x 2
#>   foo   bar
#>   <fct> <fct>
#> 1 a     b

as_tibble_row2(date)
#> # A tibble: 1 x 2
#>   foo        bar
#>   <date>     <date>
#> 1 2020-01-01 2020-01-02

[krlmlr]

as_tibble_row() doesn't document that it requires bare vectors.

We could do new_tibble(map(seq_along(x)), ~ vec_slice(x, .), nrow = 1) . However, just like #740, this requires vec_names(). Any chance we can make this available in vctrs?

[FrancoisR95]

Many thanks @lionel- and @krlmlr for your quick replies and explanations.
I still don't understand, however, what is the problem of new_tibble(as.list(x), nrow = 1) with date vectors (while I understand the problem with factors).

In your example of date vector, as.list(x) seems to have exactly the same result as vec_chop2(x).

date <- c(as.Date("2020-01-01"), as.Date("2020-01-02"))
date <- set_names(date, c("foo", "bar"))

vec_chop2(date)
#> $foo
#> [1] "2020-01-01"
#>
#> $bar
#> [1] "2020-01-02"

as.list(date)
#> $foo
#> [1] "2020-01-01"
#>
#> $bar
#> [1] "2020-01-02"

Why not, for the as_tibble_row() function, write a test like:

if (!is_bare_vector(x)) {
  if (class(x) == "Date") {
    if (!is_vector(x)) {
      cnd_signal(error_as_tibble_row_date_vector(x))
    }
  } else {  
    cnd_signal(error_as_tibble_row_bare(x))
  }
}

instead of:

if (!is_bare_vector(x)) {
  cnd_signal(error_as_tibble_row_bare(x))
}

[lionel-]

@FrancoisR95 We're looking into a more general solution that would work with any vector.

@krlmlr

We could do new_tibble(map(seq_along(x)), ~ vec_slice(x, .), nrow = 1) . However, just like #740, this requires vec_names(). Any chance we can make this available in vctrs?

Yes I think we could now expose vec_names() and vec_set_names(). How do you plan to deal with names exactly?

[krlmlr]

The names of the vector become column names here?

[lionel-]

Yup so we need to remove the inner names and use them as outer names. Also data frames should be special-cased here so I'm not sure where vec-names would come into play. That's why I thought vec-chop2 as outlined above would be appropriate for non-list and non-df inputs.

[krlmlr]

I don't follow. Yes, I can use inner names as outer names with vec_names() (forgot to actually submit that PR). Why would we special-case data frames? Wouldn't vec_slice() take care of that?

If we can make vec_chop2() available in vctrs -- fine. Maybe we can prototype here?

[lionel-]

We also need to remove the inner names otherwise they linger in the columns.

Regarding data frames, I assumed as_tibble_row(mtcars[1, ]) should be a no-op and fail if the input is not size 1? It seems strange to transform each row to a column, and would only work for data frames with row names which is strange as well.

[krlmlr]

I have a draft in 22bfa2a, not sure if I got it right. Currently, as_tibble_row() unpacks bare lists -- not sure how to keep that behavior if we allow arbitrary vectors without checking is_bare_list(). Would vec_chop2() help here?

[lionel-]

Would vec_chop2() help here?

chop2 would help giving the same implementation to atomic vectors and lists. But you could also make S3 lists follow the same code path as for bare lists if you prefer? S3 lists should be unpacked the same way as bare lists right?

[krlmlr]

vec_names2() and friends available in vctrs 0.3.2.

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