Method: Puppet::Util::Diff#lcs_diff

Defined in:
lib/puppet/util/diff.rb

#lcs_diff(data_old, data_new, format = :unified, context_lines = 3) ⇒ Object

return diff string of two input strings format defaults to unified context defaults to 3 lines



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# File 'lib/puppet/util/diff.rb', line 28

def lcs_diff(data_old, data_new, format=:unified, context_lines=3)
  unless Puppet.features.diff?
    Puppet.warning _("Cannot provide diff without the diff/lcs Ruby library")
    return ""
  end
  data_old = data_old.split(/\n/).map! { |e| e.chomp }
  data_new = data_new.split(/\n/).map! { |e| e.chomp }

  output = ""

  diffs = ::Diff::LCS.diff(data_old, data_new)
  return output if diffs.empty?

  oldhunk = hunk = nil
  file_length_difference = 0

  diffs.each do |piece|
    begin

      hunk = ::Diff::LCS::Hunk.new(
        data_old, data_new, piece,
          context_lines,

          file_length_difference)
      file_length_difference = hunk.file_length_difference
    next unless oldhunk
    # Hunks may overlap, which is why we need to be careful when our
    # diff includes lines of context. Otherwise, we might print
    # redundant lines.
    if (context_lines > 0) and hunk.overlaps?(oldhunk)
      hunk.unshift(oldhunk)
    else
      output << oldhunk.diff(format)
    end
    ensure
      oldhunk = hunk
      output << "\n"
    end
  end

  # Handle the last remaining hunk
  output << oldhunk.diff(format) << "\n"
end