Add filter to remove all ANSI color codes from the event message

lib/rackstash/filters.rb

@@ -5,6 +5,7 @@
 # This software may be modified and distributed under the terms
 # of the MIT license. See the LICENSE.txt file for details.
 
+require 'rackstash/filters/clear_color'
 require 'rackstash/filters/skip_event'
 
 module Rackstash

lib/rackstash/filters/clear_color.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+# Copyright 2017 Holger Just
+#
+# This software may be modified and distributed under the terms
+# of the MIT license. See the LICENSE.txt file for details.
+
+module Rackstash
+  module Filters
+    # Remove all ANSI color codes from the `"message"` field of the given event
+    # `Hash`.
+    class ClearColor
+      # a regular expression matching ANSI color codes
+      COLOR_REGEX = /\e\[[0-9;]*m/.freeze
+
+      # Remove all ANSI color codes from the `"message"` field. The field can
+      # either contain a single String or {Message} or an Array of those. If
+      # there is no message, we return the event unchanged.
+      #
+      # @param event [Hash] an event hash
+      # @return [Hash] the given `event` with all ANSI color codes removed from
+      #   messages
+      def call(event)
+        message = event[FIELD_MESSAGE]
+        case message
+        when Array
+          message.map! { |msg|
+            msg.gsub(COLOR_REGEX, EMPTY_STRING)
+          }
+        when String, Message
+          event[FIELD_MESSAGE] = message.gsub(COLOR_REGEX, EMPTY_STRING)
+        end
+
+        event
+      end
+    end
+  end
+end

spec/rackstash/filters/clear_color_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+# Copyright 2017 Holger Just
+#
+# This software may be modified and distributed under the terms
+# of the MIT license. See the LICENSE.txt file for details.
+
+require 'spec_helper'
+
+require 'rackstash/filters/clear_color'
+
+describe Rackstash::Filters::ClearColor do
+  let(:filter) { described_class.new }
+
+  it 'removes any ANSI color codes from the message' do
+    event = { 'message' => "Important\n\e[31mRED TEXT\e[0m\nOK" }
+    expect(filter.call(event)).to eql 'message' => "Important\nRED TEXT\nOK"
+  end
+
+  it 'removes color codes from a message array' do
+    event = {
+      'message' => ["Some \e[31mred\e[0m\nand", "some \e[32mgreen\e[0m text" ]
+    }
+    expect(filter.call(event)).to eql 'message' => [
+      "Some red\nand", "some green text"
+    ]
+  end
+
+  it 'does nothing if there is no message field' do
+    event = { 'foo' => 'bar' }
+    expect(filter.call(event)).to eql 'foo' => 'bar'
+  end
+
+end