Roo::Excelx::Cell::Empty#to_s does not return a string

[jackrg]

Empty Cell Sample.xlsx

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Steps to reproduce

Run the following code (this example in Rails):

xlsx = Roo::Excelx.new("./Empty Cell Sample.xlsx")

xlsx.each_row_streaming(pad_cells: true) do |row|
  puts row.map { |c| c.class.name }
  puts row.map { |c| c.to_s.class.name }
end

Output: irb(main):006:0> load 'EmptyCellExample.rb' Roo::Excelx::Cell::Empty Roo::Excelx::Cell::String Roo::Excelx::Cell::String Roo::Excelx::Cell::String Roo::Excelx::Cell::String Roo::Excelx::Cell::String Roo::Excelx::Cell::String Roo::Excelx::Cell::String Roo::Excelx::Cell::String Roo::Excelx::Cell::Empty Roo::Excelx::Cell::String Roo::Excelx::Cell::Empty NilClass String String String String String String String String NilClass String NilClass => true

Issue

Calling #to_s on a cell that is represented by Roo::Excelx::Cell::Empty produces nil instead of an empty string. Basic to Ruby is the tenet that calling #to_s produces a string. Workaround is to call #to_s twice (e.g. "cell.to_s.to_s")

System configuration

Roo version: 2.5.1

Ruby version: 2.0.0.p576 Empty Cell Sample.xlsx

[jackrg]

I'm going to leave this open as the basis for a strategic/tactical discussion, while I recognize that the library works as documented. The principle of "least surprise" applies here, as you would expect #each_row_streaming to return the same sort of values as #each.

[jackrg]

Just discovered another "gotcha". It looks like if the entire first column is blank (that is, it would have been eliminated if not for "pad_cells: true" in the call), each row contains a nil instead of Roo::Excelx::Cell::Empty. This means that I can't just map each cell using #value, i have to surround it with a #try (e.g. row.map! {|c| c.try(:value) } instead of row.map!(&:value).

[plusor]

I was confused when occurred this error.