(This may be related to #5948, since nested frames is a common link.)
mt <- as.data.table(mtcars)[1:3,]
mt$frm <- list(data.frame(a=1), data.frame(a=1), data.frame(a=1))
mt
# Error in vapply(X = x, FUN = fun, ..., FUN.VALUE = NA_character_, USE.NAMES = use.names) :
# values must be type 'character',
# but FUN(X[[1]]) result is type 'list'
mt[,-12]
# mpg cyl disp hp drat wt qsec vs am gear carb
# <num> <num> <num> <num> <num> <num> <num> <num> <num> <num> <num>
# 1: 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
# 2: 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
# 3: 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
When debugging,
debug(data.table:::format_col.default)
mt
#### 'c'ontinue through the first 11 columns, then
x
# [[1]]
# a
# 1 1
# [[2]]
# a
# 1 1
# [[3]]
# a
# 1 1
vapply_1c(x, format_list_item, ...)
# Error in vapply(X = x, FUN = fun, ..., FUN.VALUE = NA_character_, USE.NAMES = use.names) :
# values must be type 'character',
# but FUN(X[[1]]) result is type 'list'
format_list_item(x[[1]])
# a
# 1 1
Where it is assumed that all return values from vapply_1c are expected to be strings.
Note that this does not fail when the nested frames are more than one column, since format_list_item.default perhaps-naively uses length(format(..)) == 1.
mt$frm <- list(data.frame(a=1,b=1), data.frame(), data.frame(a=1,b=1))
mt
# mpg cyl disp hp drat wt qsec vs am gear carb frm
# <num> <num> <num> <num> <num> <num> <num> <num> <num> <num> <num> <list>
# 1: 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4 <data.frame[1x2]>
# 2: 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4 <data.frame[0x0]>
# 3: 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1 <data.frame[1x2]>
I don't know if it makes sense to define format_list_item.data.frame as well to preclude this, or if there are better methods:
format_list_item.data.frame <- function(x, ...) "<multi-column>"
vapply_1c(x, format_list_item.data.frame, ...)
# [1] "<multi-column>" "<multi-column>" "<multi-column>"
This test was done with data.table_1.16.2, but it also fails with data.table_1.15.2, so it's not a recent breakage.
packageVersion("data.table")
# [1] ‘1.15.2’
mt <- as.data.table(mtcars)[1:3,]
mt$frm <- list(data.frame(a=1), data.frame(a=1), data.frame(a=1))
mt
# Error in vapply(X = x, FUN = fun, ..., FUN.VALUE = NA_character_, USE.NAMES = use.names) :
# values must be type 'character',
# but FUN(X[[1]]) result is type 'list'
sessionInfo()
sessionInfo()
# R version 4.3.3 (2024-02-29)
# Platform: x86_64-pc-linux-gnu (64-bit)
# Running under: Ubuntu 24.04.1 LTS
# Matrix products: default
# BLAS: /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3
# LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.26.so; LAPACK version 3.12.0
# locale:
# [1] LC_CTYPE=C.UTF-8 LC_NUMERIC=C LC_TIME=C.UTF-8 LC_COLLATE=C.UTF-8 LC_MONETARY=C.UTF-8 LC_MESSAGES=C.UTF-8
# [7] LC_PAPER=C.UTF-8 LC_NAME=C LC_ADDRESS=C LC_TELEPHONE=C LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C
# time zone: America/New_York
# tzcode source: system (glibc)
# attached base packages:
# [1] stats graphics grDevices utils datasets methods base
# other attached packages:
# [1] data.table_1.16.2 r2_0.11.0
# loaded via a namespace (and not attached):
# [1] compiler_4.3.3 clipr_0.8.0 fastmap_1.2.0 cli_3.6.2 tools_4.3.3 htmltools_0.5.8.1 rmarkdown_2.26 knitr_1.45
# [9] xfun_0.42 digest_0.6.34 rlang_1.1.3 evaluate_0.23
(This may be related to #5948, since nested frames is a common link.)
When debugging,
Where it is assumed that all return values from vapply_1c are expected to be strings.
Note that this does not fail when the nested frames are more than one column, since format_list_item.default perhaps-naively uses length(format(..)) == 1.
I don't know if it makes sense to define format_list_item.data.frame as well to preclude this, or if there are better methods:
This test was done with data.table_1.16.2, but it also fails with data.table_1.15.2, so it's not a recent breakage.