Calculate Fog expiration taking DST into account

Fixes carrierwaveuploader#2059

lib/carrierwave/storage/fog.rb

@@ -200,7 +200,7 @@ def authenticated_url(options = {})
             # avoid a get by using local references
             local_directory = connection.directories.new(:key => @uploader.fog_directory)
             local_file = local_directory.files.new(:key => path)
-            expire_at = options[:expire_at] || ::Fog::Time.now + @uploader.fog_authenticated_url_expiration
+            expire_at = options[:expire_at] || ::Fog::Time.now.since(@uploader.fog_authenticated_url_expiration.to_i)
             case @uploader.fog_credentials[:provider]
               when 'AWS', 'Google'
                 # Older versions of fog-google do not support options as a parameter

spec/spec_helper.rb

@@ -17,7 +17,7 @@
 require 'open-uri'
 require "webmock/rspec"
 require 'mini_magick'
-require "vips"
+require 'active_support/core_ext'
 
 I18n.enforce_available_locales = false
 

spec/storage/fog_helper.rb

@@ -533,6 +533,34 @@ def check_file
             end
           end
 
+          context 'in a timezone with DST' do
+            before do
+              @prev_tz = ENV['TZ']
+              ENV['TZ'] = 'US/Pacific'
+            end
+            after { ENV['TZ'] = @prev_tz }
+
+            it "should generate a proper X-Amz-Expires when expires spans a move to DST" do
+              if @provider == 'AWS'
+                Timecop.freeze(Time.at(1477932000)) do |now|
+                  expiration = 7 * 24 * 60 * 60 # 1 week
+                  allow(@uploader).to receive(:fog_authenticated_url_expiration).and_return(expiration)
+                  expect(@fog_file.authenticated_url).to include("X-Amz-Expires=#{expiration.to_s}")
+                end
+              end
+            end
+
+            it "should generate a proper X-Amz-Expires when expires spans a move to DST and an ActiveRecord::Duration is provided" do
+              if @provider == 'AWS'
+                Timecop.freeze(Time.at(1477932000)) do |now|
+                  expiration = 1.week
+                  allow(@uploader).to receive(:fog_authenticated_url_expiration).and_return(expiration)
+                  expect(@fog_file.authenticated_url).to include("X-Amz-Expires=#{expiration.to_s}")
+                end
+              end
+            end
+          end
+
           it 'should generate correct filename' do
             expect(@fog_file.filename).to eq('private.txt')
           end