Spec to check for whitespace issues in your codebase. Tweak/contribute your patches!

whitespace_spec.rb

RSpec::Matchers.define :have_standardized_whitespaces do
  failure_message_for_should do |actual|
    whitespace_errors_for(actual).join("\n")
  end

  match do |actual|
    whitespace_errors_for(actual).empty?
  end

  class WhitespaceCheck < Struct.new(:pattern, :message)
    def lines
      @lines ||= []
    end

    def check(line, number)
      lines << number if line =~ pattern
    end

    def error_for(file)
      "#{file} #{message} on lines #{lines.join(',')}" unless lines.empty?
    end
  end

  def whitespace_errors_for(files)
    @whitespace_errors ||= files.inject([]) do |errors, filename|
      whitespace_checks = [
        WhitespaceCheck.new(/\s+\n$/, "has EOL spaces"),
        WhitespaceCheck.new(/\r/, "has DOS EOL characters"),
        WhitespaceCheck.new(/\t/, "has tab characters")
      ]

      File.readlines(filename).each_with_index do |line, number|
        whitespace_checks.each {|w| w.check(line, number+1)}
      end

      errors += whitespace_checks.map {|m| m.error_for(filename)}.compact
    end
  end
end

describe "The codebase" do
  around(:each) do |example|
    Dir.chdir(File.expand_path("../..", __FILE__)) { example.run }
  end

  let(:filter) { /^(app|lib|spec).*\.(rb|rake)$/ }
  subject { `git ls-files -c -m -o`.split("\n").select {|f| f =~ filter} }
  it { should have_standardized_whitespaces }
end