Processing malformed files with FasterCSV

On a recent project, I had to implement a CSV parser that would gracefully handle malformed files. I’m talking about files with unescaped quotes, wacky UTF-8 chars, and various other abominations of nature.

I originally assumed FasterCSV would handle this automagically, but it turns out that the library’s most commonly used methods are pretty strict when it comes to handling CSV files.

For example, parsing a malformed file one line at a time will result in an exception being thrown, even before any rows are yielded to the block:

FasterCSV.foreach("malformed.csv") do |row|
  # use row here...

Not cool! I managed to get around this by manually looping over each row and rescuing a malformed CSV exception if one gets thrown:"malformed.csv", "rb") do |output|
  loop do
      break unless row = output.shift
      # use row here...
    rescue FasterCSV::MalformedCSVError => e
      # handle malformed row here...

Anyone have a better way to do this?

6 thoughts on “Processing malformed files with FasterCSV

  1. But how do you actually capture the offending row so you can at least log it? You would think something like output.gets or something, but I can’t figure it out. Not a big fan of FasterCSV at this point.

  2. That really does look nasty. I’m wondering if it would be better to use #parse inside of a begin/rescue block and then just work with each row as an Array outside of FasterCSV.

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