Bug #15910: $. doesn't hold the linenumber anymore when reading a CSV-file using the CSV class

• Status: Rejected
• Assignee: kou (Kouhei Sutou)
• Target version: -
• ruby -v: ruby 2.6.3p62 (2019-04-16 revision 67580) [x86_64-cygwin]
• Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN

[rovf (Ronald Fischer)]

Example program:

require 'csv'
IFS=';'
CSV_OPTIONS = { col_sep: IFS, external_encoding: Encoding::ISO_8859_1, internal_encoding: Encoding::UTF_8 }
CSV.new($stdin, CSV_OPTIONS).each do
    |row|
    puts "::::line #{$.} row=#{row}"
end%          

With this program, I could dump a semicolon-delimited CSV file, with line numbers. Now the line number always displays as 0. Has the implementation of CSV changed?

See also https://stackoverflow.com/questions/56524941/is-special-variable-gone-from-ruby

[jeremyevans0 (Jeremy Evans)]

• Assignee set to kou (Kouhei Sutou)

I can confirm the behavior change. I bisected it to https://github.com/ruby/csv/commit/8505ff0900a4789dce0740ab23e92de1fb89196e. I would not consider this change a bug, since I don't think the csv library was ever documented as treating $. as the line number of the current CSV file. I would consider it relying on internal behavior. Restoring backwards compatibility in regards to $. looks like it may hurt performance. Assigning to kou, csv maintainer, to make a decision.

[kou (Kouhei Sutou)]

• Status changed from Open to Rejected

CSV implementation was changed to improve performance. The new implementation reads data as chunk ($stdin.gets(nil, 4096)) instead of lines ($stdin.gets) from input. $. doesn't work with reading data as chunk.

It's backward incompatible but I don't want to keep the previous behavior. Because it blocks performance improvement.

You can use CSV#lineno as alternative:

require 'csv'
IFS=';'
CSV_OPTIONS = { col_sep: IFS, external_encoding: Encoding::ISO_8859_1, internal_encoding: Encoding::UTF_8 }
csv = CSV.new($stdin, CSV_OPTIONS)
csv.each do |row|
  puts "::::line #{csv.lineno} row=#{row}"
end

CSV#lineno reports logical line number. If your CSV data has a record that includes new lines:

a;"with
new
line"
b;c

CSV#lineno reports 1 for a;"with\nnew\nline" row and 2 for b;c row.

If your CSV data doesn't have these rows, you can use CSV#lineno as alternative of $..