Fix multithreaded fail on trailing empty column

src/detection.jl

@@ -348,6 +348,11 @@ end
 function findchunkrowstart(ranges, i, buf, opts, typemap, downcast, ncols, rows_to_check, columns, origcoltypes, columnlock, @nospecialize(stringtype), totalbytes, totalrows, succeeded)
     pos = ranges[i]
     len = ranges[i + 1] - 1
+    addtrailingcolumn = false # set if the file ends with an empty column with no trailing newline
+    if i == length(ranges)-1
+        len += 1 # correctly handle the absence of a trailing newline
+        addtrailingcolumn = Parsers.delimited(Parsers.xparse(String, buf, len, len, opts).code)
+    end
     nextrowpos = 0
     startpos = pos
     code = Parsers.ReturnCode(0)
@@ -394,6 +399,7 @@ function findchunkrowstart(ranges, i, buf, opts, typemap, downcast, ncols, rows_
             rowsparsed += ((pos < len) | (numcolsthisrow != 0)) # trailing newline does not count
             parsedncols += numcolsthisrow
         end
+        parsedncols += addtrailingcolumn
         lock(columnlock) do
             for i = 1:ncols
                 cp = columnprops[i]
@@ -475,8 +481,8 @@ function findrowstarts!(buf, opts, ranges, ncols, columns, @nospecialize(stringt
     while ranges[new_last_idx] > stop
         new_last_idx -= 1
     end
-    ranges[new_last_idx+1] = stop
     resize!(ranges, new_last_idx+1)
+    ranges[end] = stop
     unique!(ranges) # in case multiple tasks start on the same row
     newranges = similar(ranges)
     N = length(ranges) - 1

test/testfiles.jl

@@ -687,6 +687,11 @@ testfiles = [
         NamedTuple{(:x, :y), Tuple{Int, Int}},
         (x = [15887, 23603], y = [24651, 14076])
     ),
+    ("test_trailing_empty_column.csv", (ntasks=3,),
+        (14,3),
+        NamedTuple{(:X,:Y,:Z), Tuple{Int, Union{Missing,String7}, Union{Missing,Float64}}},
+        nothing
+    )
 ];
 
 @static if VERSION >= v"1.3-DEV"

test/testfiles/test_trailing_empty_column.csv

@@ -0,0 +1,15 @@
+X,Y,Z
+1,aaaa,.1
+2,bbbb,.2
+3,cccc,.3
+4,dddd,.4
+5,eeee,.5
+6,ffff,.6
+7,gggg,.7
+8,hhhh,.8
+9,iiii,.9
+10,jjjj,.10
+11,kkkk,.11
+12,llll,.12
+13,mmmm,.13
+14,,