[ruby/csv] Use "\n" for the default row separator on Ruby 3.0 or later

https://github.com/ruby/csv/commit/1f9cbc170e

lib/csv.rb

@@ -90,11 +90,11 @@
 # with any questions.
 
 require "forwardable"
-require "English"
 require "date"
 require "stringio"
 
 require_relative "csv/fields_converter"
+require_relative "csv/input_record_separator"
 require_relative "csv/match_p"
 require_relative "csv/parser"
 require_relative "csv/row"
@@ -1051,7 +1051,7 @@ class CSV
     #   out_string # => "FOO,0000\nBAR,1111\nBAZ,2222\n"
     def filter(input=nil, output=nil, **options)
       # parse options for input, output, or both
-      in_options, out_options = Hash.new, {row_sep: $INPUT_RECORD_SEPARATOR}
+      in_options, out_options = Hash.new, {row_sep: InputRecordSeparator.value}
       options.each do |key, value|
         case key.to_s
         when /\Ain(?:put)?_(.+)\Z/
@@ -1292,8 +1292,8 @@ class CSV
     # Argument +ary+ must be an \Array.
     #
     # Special options:
-    # * Option <tt>:row_sep</tt> defaults to <tt>$INPUT_RECORD_SEPARATOR</tt>
+    # * Option <tt>:row_sep</tt> defaults to <tt>"\n"> on Ruby 3.0 or later
-    #   (<tt>$/</tt>).:
+    #   and <tt>$INPUT_RECORD_SEPARATOR</tt> (<tt>$/</tt>) otherwise.:
     #     $INPUT_RECORD_SEPARATOR # => "\n"
     # * This method accepts an additional option, <tt>:encoding</tt>, which sets the base
     #   Encoding for the output. This method will try to guess your Encoding from
@@ -1315,7 +1315,7 @@ class CSV
     #   CSV.generate_line(:foo)
     #
     def generate_line(row, **options)
-      options = {row_sep: $INPUT_RECORD_SEPARATOR}.merge(options)
+      options = {row_sep: InputRecordSeparator.value}.merge(options)
       str = +""
       if options[:encoding]
         str.force_encoding(options[:encoding])

lib/csv/input_record_separator.rb

@@ -0,0 +1,31 @@
+require "English"
+require "stringio"
+
+class CSV
+  module InputRecordSeparator
+    class << self
+      is_input_record_separator_deprecated = false
+      verbose, $VERBOSE = $VERBOSE, true
+      stderr, $stderr = $stderr, StringIO.new
+      input_record_separator = $INPUT_RECORD_SEPARATOR
+      begin
+        $INPUT_RECORD_SEPARATOR = "\r\n"
+        is_input_record_separator_deprecated = (not $stderr.string.empty?)
+      ensure
+        $INPUT_RECORD_SEPARATOR = input_record_separator
+        $stderr = stderr
+        $VERBOSE = verbose
+      end
+
+      if is_input_record_separator_deprecated
+        def value
+          "\n"
+        end
+      else
+        def value
+          $INPUT_RECORD_SEPARATOR
+        end
+      end
+    end
+  end
+end

lib/csv/parser.rb

@@ -3,6 +3,7 @@
 require "strscan"
 
 require_relative "delete_suffix"
+require_relative "input_record_separator"
 require_relative "match_p"
 require_relative "row"
 require_relative "table"
@@ -605,7 +606,7 @@ class CSV
             # do nothing:  ensure will set default
           end
         end
-        separator = $INPUT_RECORD_SEPARATOR if separator == :auto
+        separator = InputRecordSeparator.value if separator == :auto
       end
       separator.to_s.encode(@encoding)
     end

lib/csv/writer.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require_relative "input_record_separator"
 require_relative "match_p"
 require_relative "row"
 
@@ -133,7 +134,7 @@ class CSV
       @column_separator = @options[:column_separator].to_s.encode(@encoding)
       row_separator = @options[:row_separator]
       if row_separator == :auto
-        @row_separator = $INPUT_RECORD_SEPARATOR.encode(@encoding)
+        @row_separator = InputRecordSeparator.value.encode(@encoding)
       else
         @row_separator = row_separator.to_s.encode(@encoding)
       end