fread fail to read single row single column datetime field

[jangorecki]

single row, single column datetime is not read, after adding extra column it works fine.

data.table::fread("c1\n2018-01-31 03:16:57")
#Empty data.table (0 rows) of 2 cols: V1,c1
#Warning message:
#In data.table::fread("c1\n2018-01-31 03:16:57") :
#  Detected 1 column names but the data has 2 columns (i.e. an invalid file format). Added 1 extra default column name for the first column which is guessed to be row names or an index. Use setnames() afterwards if this guess is not correct, or fix the file write command that created the file to create a valid file.
data.table::fread("c1,c2\n2018-01-31 03:16:57,b")
#                    c1 c2
#1: 2018-01-31 03:16:57  

@MichaelChirico

[MichaelChirico]

Current output is better than the original issue:

data.table::fread("c1\n2018-01-31 03:16:57")
#            V1       c1
#        <char>   <char>
# 1: 2018-01-31 03:16:57

sep=',' fixes the issue overall, the problem is it detects sep=' '.

#4464 also doesn't solve:

data.table::fread("c1\n2018-01-31 03:16:57")
#            V1       c1
#        <IDat>   <char>
# 1: 2018-01-31 03:16:57

vs

data.table::fread("c1\n2018-01-31 03:16:57", sep = ',')
#                     c1
#                 <POSc>
# 1: 2018-01-31 03:16:57

IINM sep detection happens before type detection, which is why IDate is detected when we don't specify sep.

I would close now... behavior seems pretty acceptable overall.

[jangorecki]

Agree, adding sep solves the problem, and current warning is good as well. I wIll add unit tests before closing.