Added partial days support to DateTime's advance method.

You can now add partial days (e.g. 2.5.days) to `DateTime` with the advance method.
This was acheived by mimicing the `advance` implementation in `Time`.

activesupport/CHANGELOG.md

@@ -189,4 +189,8 @@
 
     *Daniel Schierbeck*
 
+*   DateTime `advance` now supports partial days (`days: 1.5`)
+
+    *Shay Davidson*
+
 Please check [4-0-stable](https://github.com/rails/rails/blob/4-0-stable/activesupport/CHANGELOG.md) for previous changes.

activesupport/lib/active_support/core_ext/date_time/calculations.rb

@@ -53,17 +53,27 @@ class DateTime
   # <tt>:months</tt>, <tt>:weeks</tt>, <tt>:days</tt>, <tt>:hours</tt>,
   # <tt>:minutes</tt>, <tt>:seconds</tt>.
   def advance(options)
+    unless options[:weeks].nil?
+      options[:weeks], partial_weeks = options[:weeks].divmod(1)
+      options[:days] = options.fetch(:days, 0) + 7 * partial_weeks
+    end
+
+    unless options[:days].nil?
+      options[:days], partial_days = options[:days].divmod(1)
+      options[:hours] = options.fetch(:hours, 0) + 24 * partial_days
+    end
+
     d = to_date.advance(options)
-    datetime_advanced_by_date = change(:year => d.year, :month => d.month, :day => d.day)
+    time_advanced_by_date = change(:year => d.year, :month => d.month, :day => d.day)
     seconds_to_advance = \
       options.fetch(:seconds, 0) +
-      options.fetch(:minutes, 0) * 60 +
-      options.fetch(:hours, 0) * 3600
+        options.fetch(:minutes, 0) * 60 +
+        options.fetch(:hours, 0) * 3600
 
     if seconds_to_advance.zero?
-      datetime_advanced_by_date
+      time_advanced_by_date
     else
-      datetime_advanced_by_date.since seconds_to_advance
+      time_advanced_by_date.since(seconds_to_advance)
     end
   end
 

activesupport/test/core_ext/date_time_ext_test.rb

@@ -162,6 +162,12 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal DateTime.civil(2013,10,17,20,22,19), DateTime.civil(2005,2,28,15,15,10).advance(:years => 7, :months => 19, :weeks => 2, :days => 5, :hours => 5, :minutes => 7, :seconds => 9)
   end
 
+  def test_advance_partial_days
+    assert_equal DateTime.civil(2012,9,29,13,15,10),  DateTime.civil(2012,9,28,1,15,10).advance(:days => 1.5)
+    assert_equal DateTime.civil(2012,9,28,13,15,10),  DateTime.civil(2012,9,28,1,15,10).advance(:days => 0.5)
+    assert_equal DateTime.civil(2012,10,29,13,15,10), DateTime.civil(2012,9,28,1,15,10).advance(:days => 1.5, :months => 1)
+  end
+
   def test_advanced_processes_first_the_date_deltas_and_then_the_time_deltas
     # If the time deltas were processed first, the following datetimes would be advanced to 2010/04/01 instead.
     assert_equal DateTime.civil(2010, 3, 29), DateTime.civil(2010, 2, 28, 23, 59, 59).advance(:months => 1, :seconds => 1)