TimeWithZone caches TZInfo::TimezonePeriod used for time conversion so that it can be reused, and enforces DST rules correctly when instance is created from a local time

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@9040 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

4 files changed, 55 insertions, 16 deletions

diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index cd0106c0b5..d72fdadf3f 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* TimeWithZone caches TZInfo::TimezonePeriod used for time conversion so that it can be reused, and enforces DST rules correctly when instance is created from a local time [Geoff Buesing]
+
 * Fixed that BufferedLogger should create its own directory if one doesn't already exist #11285 [lotswholetime]
 
 * Fix Numeric time tests broken by DST change by anchoring them to fixed times instead of Time.now. Anchor TimeZone#now DST test to time specified with Time.at instead of Time.local to work around platform differences with Time.local and DST representation [Geoff Buesing]
diff --git a/activesupport/lib/active_support/time_with_zone.rb b/activesupport/lib/active_support/time_with_zone.rb
index 008c7f151b..68585e8273 100644
--- a/activesupport/lib/active_support/time_with_zone.rb
+++ b/activesupport/lib/active_support/time_with_zone.rb
@@ -5,29 +5,28 @@ module ActiveSupport
     include Comparable
     attr_reader :time_zone
   
-    def initialize(utc_time, time_zone, local_time = nil)
-      @utc = utc_time
-      @time = local_time
-      @time_zone = time_zone
+    def initialize(utc_time, time_zone, local_time = nil, period = nil)
+      @utc, @time_zone, @time = utc_time, time_zone, local_time
+      @period = @utc ? period : get_period_and_ensure_valid_local_time
     end
   
     # Returns a Time instance that represents the time in time_zone
     def time
-      @time ||= time_zone.utc_to_local(@utc)
+      @time ||= utc_to_local
     end
 
     # Returns a Time instance that represents the time in UTC
     def utc
-      @utc ||= time_zone.local_to_utc(@time)
+      @utc ||= local_to_utc
     end
     alias_method :comparable_time, :utc
     alias_method :getgm, :utc
     alias_method :getutc, :utc
     alias_method :gmtime, :utc
   
-    # Returns the underlying TZInfo::TimezonePeriod for the local time
+    # Returns the underlying TZInfo::TimezonePeriod
     def period
-      @period ||= time_zone.period_for_utc(utc)
+      @period ||= time_zone.period_for_utc(@utc)
     end
 
     # Returns the simultaneous time in the specified zone
@@ -214,5 +213,24 @@ module ActiveSupport
       result = result.in_time_zone(time_zone) if result.acts_like?(:time)
       result
     end
+    
+    private      
+      def get_period_and_ensure_valid_local_time
+        @time_zone.period_for_local(@time)
+      rescue ::TZInfo::PeriodNotFound
+        # time is in the "spring forward" hour gap, so we're moving the time forward one hour and trying again
+        @time += 1.hour
+        retry
+      end
+    
+      # Replicating logic from TZInfo::Timezone#utc_to_local because we want to cache the period in an instance variable for reuse
+      def utc_to_local
+        ::TZInfo::TimeOrDateTime.wrap(utc) {|utc| period.to_local(utc)}
+      end
+      
+      # Replicating logic from TZInfo::Timezone#local_to_utc because we want to cache the period in an instance variable for reuse
+      def local_to_utc
+        ::TZInfo::TimeOrDateTime.wrap(time) {|time| period.to_utc(time)}
+      end
   end
 end
diff --git a/activesupport/lib/active_support/values/time_zone.rb b/activesupport/lib/active_support/values/time_zone.rb
index a52eee3e7c..401b669a0a 100644
--- a/activesupport/lib/active_support/values/time_zone.rb
+++ b/activesupport/lib/active_support/values/time_zone.rb
@@ -183,14 +183,8 @@ class TimeZone
     #   Time.zone = "Hawaii"                      # => "Hawaii"
     #   Time.zone.local(2007, 2, 1, 15, 30, 45)   # => Thu, 01 Feb 2007 15:30:45 HST -10:00
     def local(*args)
-      t = Time.utc_time(*args)
-      begin
-        result = local_to_utc(t)
-      rescue TZInfo::PeriodNotFound
-        t += 1.hour
-        retry
-      end
-      result.in_time_zone(self)
+      time = Time.utc_time(*args)
+      ActiveSupport::TimeWithZone.new(nil, self, time)
     end
     
     # Returns an ActiveSupport::TimeWithZone instance representing the current time
diff --git a/activesupport/test/core_ext/time_with_zone_test.rb b/activesupport/test/core_ext/time_with_zone_test.rb
index a3566796a7..5f1a002071 100644
--- a/activesupport/test/core_ext/time_with_zone_test.rb
+++ b/activesupport/test/core_ext/time_with_zone_test.rb
@@ -256,6 +256,31 @@ uses_tzinfo 'TimeWithZoneTest' do
       assert_equal 17, twz.sec
       assert_equal 500, twz.usec
     end
+    
+    def test_utc_to_local_conversion_saves_period_in_instance_variable
+      assert_nil @twz.instance_variable_get('@period')
+      @twz.time
+      assert_kind_of TZInfo::TimezonePeriod, @twz.instance_variable_get('@period')
+    end
+    
+    def test_instance_created_with_local_time_returns_correct_utc_time
+      twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(1999, 12, 31, 19))
+      assert_equal Time.utc(2000), twz.utc
+    end
+    
+    def test_instance_created_with_local_time_enforces_spring_dst_rules
+      twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,4,2,2)) # first second of DST
+      assert_equal Time.utc(2006,4,2,3), twz.time # springs forward to 3AM
+      assert_equal true, twz.dst?
+      assert_equal 'EDT', twz.zone
+    end
+    
+    def test_instance_created_with_local_time_enforces_fall_dst_rules
+      twz = ActiveSupport::TimeWithZone.new(nil, @time_zone, Time.utc(2006,10,29,1)) # 1AM can be either DST or non-DST; we'll pick DST
+      assert_equal Time.utc(2006,10,29,1), twz.time
+      assert_equal true, twz.dst?
+      assert_equal 'EDT', twz.zone
+    end
   end
   
   class TimeWithZoneMethodsForTimeAndDateTimeTest < Test::Unit::TestCase