Add LTSV formatter and its spec

.travis.yml

@@ -7,6 +7,9 @@ rvm:
   - jruby
   - jruby-head
   - rbx-2
+matrix:
+  allow_failures:
+    - rvm: jruby-head
 env:
   global:
     - JRUBY_OPTS='-J-XX:+TieredCompilation -J-XX:TieredStopAtLevel=1 -J-Djruby.compile.mode=OFF -J-Djruby.compile.invokedynamic=false'

lib/lograge.rb

@@ -6,6 +6,7 @@
 require 'lograge/formatters/l2met'
 require 'lograge/formatters/lines'
 require 'lograge/formatters/logstash'
+require 'lograge/formatters/ltsv'
 require 'lograge/formatters/raw'
 require 'lograge/log_subscriber'
 require 'active_support/core_ext/module/attribute_accessors'

lib/lograge/formatters/ltsv.rb

@@ -0,0 +1,43 @@
+module Lograge
+  module Formatters
+    class LTSV
+      def call(data)
+        fields = fields_to_display(data)
+
+        event = fields.map { |key| format(key, data[key]) }
+        event.join('\t')
+      end
+
+      def fields_to_display(data)
+        data.keys
+      end
+
+      def format(key, value)
+        if key == :error
+          # Exactly preserve the previous output
+          # Parsing this can be ambigious if the error messages contains
+          # a single quote
+          value = "'#{escape value}'"
+        else
+          # Ensure that we always have exactly two decimals
+          value = Kernel.format('%.2f', value) if value.is_a? Float
+        end
+
+        "#{key}:#{value}"
+      end
+
+      private
+
+      def escape(string)
+        value = string.is_a?(String) ? string.dup : string.to_s
+
+        value.gsub!('\\', '\\\\')
+        value.gsub!('\n', '\\n')
+        value.gsub!('\r', '\\r')
+        value.gsub!('\t', '\\t')
+
+        value
+      end
+    end
+  end
+end

spec/formatters/ltsv_spec.rb

@@ -0,0 +1,29 @@
+require 'lograge'
+
+describe Lograge::Formatters::LTSV do
+  let(:payload) do
+    {
+      custom: 'data',
+      status: 200,
+      method: 'GET',
+      path: '/',
+      controller: 'welcome',
+      action: 'index',
+      will_escaped: '\t'
+    }
+  end
+
+  subject { described_class.new.call(payload) }
+
+  it "includes the 'controller' key:value" do
+    expect(subject).to include('controller:welcome')
+  end
+
+  it "includes the 'action' key:value" do
+    expect(subject).to include('action:index')
+  end
+
+  it 'escapes escape sequences as value' do
+    expect(subject).to include('will_escaped:\\t')
+  end
+end