如何进一步处理导致 Ruby FasterCSV 库抛出 MalformedCSVError 的数据行？

传入数据文件包含格式错误的 CSV 数据（例如非转义引号）以及（有效）CSV 数据（例如包含换行符的字段）。如果检测到 CSV 格式错误，我想对该数据使用替代例程。

使用以下示例代码（为简单起见进行了缩写）

FasterCSV.open( file ){|csv|
  row = true
  while row
    begin
      row = csv.shift
      break unless row
      # Do things with the good rows here...

    rescue FasterCSV::MalformedCSVError => e
      # Do things with the bad rows here...
      next
    end
  end
}

MalformedCSVError 是在 csv.shift 方法中引起的。如何从救援子句中访问导致错误的数据？

require 'csv' #CSV in ruby 1.9.2 is identical to FasterCSV

# File.open('test.txt','r').each do |line|
DATA.each do |line|
  begin
    CSV.parse(line) do |row|
      p row #handle row
    end
  rescue  CSV::MalformedCSVError => er
    puts er.message
    puts "This one: #{line}"
    # and continue
  end
end

# Output:

# Unclosed quoted field on line 1.
# This one: 1,"aaa
# Illegal quoting on line 1.
# This one: aaa",valid
# Unclosed quoted field on line 1.
# This one: 2,"bbb
# ["bbb", "invalid"]
# ["3", "ccc", "valid"]   

__END__
1,"aaa
aaa",valid
2,"bbb
bbb,invalid
3,ccc,valid

只需将文件逐行输入 FasterCSV 并修复错误即可。