Change the file root extract logic to allow folder to have dynamic part in it

Fixes #4

Author: ph

lib/logstash/outputs/file.rb

@@ -7,6 +7,7 @@
 # This output will write events to files on disk. You can use fields
 # from the event as parts of the filename and/or path.
 class LogStash::Outputs::File < LogStash::Outputs::Base
+ FIELD_REF = /%\{[^}]+\}/
 
  config_name "file"
  milestone 2
@@ -126,7 +127,7 @@ def generate_filepath(event)
 
  private
  def path_with_field_ref?
- path =~ /%\{[^}]+\}/
+ path =~ FIELD_REF
  end
 
  def format_message(event)
@@ -138,8 +139,8 @@ def format_message(event)
  end
 
  def extract_file_root
- extracted_path = File.expand_path(path.gsub(/%{.+/, ''))
- Pathname.new(extracted_path).expand_path
+ parts = File.expand_path(path).split(File::SEPARATOR)
+ parts.take_while { |part| part !~ FIELD_REF }.join(File::SEPARATOR)
  end
 
  def teardown

spec/outputs/file_spec.rb

@@ -186,6 +186,23 @@
  end
  end
 
+ it 'write the events to a file when some part of a folder or file is dynamic' do
+ t = Time.now
+ good_event = LogStash::Event.new("@timestamp" => t)
+
+ Stud::Temporary.directory do |path|
+ dynamic_path = "#{path}/failed_syslog-%{+YYYY-MM-dd}"
+ expected_path = "#{path}/failed_syslog-#{t.strftime("%Y-%m-%d")}"
+
+ config = { "path" => dynamic_path }
+ output = LogStash::Outputs::File.new(config)
+ output.register
+ output.receive(good_event)
+
+ expect(File.exist?(expected_path)).to eq(true)
+ end
+ end
+
  it 'write the event to the generated filename with multiple deep' do
  good_event = LogStash::Event.new
  good_event['error'] = '/inside/errors/42.txt'