Add Time.days_in_month, and make Time#next_month work when invoked on the 31st of a month

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@2082 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

3 files changed, 54 insertions, 5 deletions

diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 315ea30568..b1f81fdf1b 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Add Time.days_in_month, and make Time#next_month work when invoked on the 31st of a month
+
 * Fixed that Time#midnight would have a non-zero usec on some platforms #1836
 
 * Fixed inflections of "index/indices" #1766 [damn_pepe@gmail.com]
diff --git a/activesupport/lib/active_support/core_ext/time/calculations.rb b/activesupport/lib/active_support/core_ext/time/calculations.rb
index 503717f4fe..76d6d4c176 100644
--- a/activesupport/lib/active_support/core_ext/time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/time/calculations.rb
@@ -3,6 +3,23 @@ module ActiveSupport #:nodoc:
     module Time #:nodoc:
       # Enables the use of time calculations within Time itself
       module Calculations
+        def self.append_features(base) #:nodoc:
+          super
+          base.extend(ClassMethods)
+        end
+
+        module ClassMethods
+          def days_in_month(month, year=nil)
+            if month == 2
+              (year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0)) ?  29 : 28
+            elsif month <= 7
+              month % 2 == 0 ? 30 : 31
+            else
+              month % 2 == 0 ? 31 : 30
+            end
+          end
+        end
+
         # Seconds since midnight: Time.now.seconds_since_midnight
         def seconds_since_midnight
           self.hour.hours + self.min.minutes + self.sec + (self.usec/1.0e+6)
@@ -47,12 +64,18 @@ module ActiveSupport #:nodoc:
         end
 
         def months_since(months)
-          if months + self.month > 12
-            old_time = self
-            change(:year => self.year + 1, :month => 1).months_since(months + old_time.month - 12 - 1)
-          else
-            change(:year => self.year, :month => self.month + months)
+          year, month, mday = self.year, self.month, self.mday
+
+          month += months
+          while month > 12
+            month -= 12
+            year += 1
           end
+
+          max = ::Time.days_in_month(month, year)
+          mday = max if mday > max
+
+          change(:year => year, :month => month, :mday => mday)
         end
 
         # Returns a new Time representing the time a number of specified years ago
diff --git a/activesupport/test/core_ext/time_ext_test.rb b/activesupport/test/core_ext/time_ext_test.rb
index dca810d67e..ca58cd0a8a 100644
--- a/activesupport/test/core_ext/time_ext_test.rb
+++ b/activesupport/test/core_ext/time_ext_test.rb
@@ -137,4 +137,28 @@ class TimeExtCalculationsTest < Test::Unit::TestCase
     midnight = Time.local(2005, 2, 21, 0, 0, 0)
     assert_equal midnight.midnight, (midnight + 1.hour + 0.000001).midnight
   end
+
+  def test_days_in_month
+    assert_equal 31, Time.days_in_month(1, 2005)
+
+    assert_equal 28, Time.days_in_month(2, 2005)
+    assert_equal 29, Time.days_in_month(2, 2004)
+    assert_equal 29, Time.days_in_month(2, 2000)
+    assert_equal 28, Time.days_in_month(2, 1900)
+
+    assert_equal 31, Time.days_in_month(3, 2005)
+    assert_equal 30, Time.days_in_month(4, 2005)
+    assert_equal 31, Time.days_in_month(5, 2005)
+    assert_equal 30, Time.days_in_month(6, 2005)
+    assert_equal 31, Time.days_in_month(7, 2005)
+    assert_equal 31, Time.days_in_month(8, 2005)
+    assert_equal 30, Time.days_in_month(9, 2005)
+    assert_equal 31, Time.days_in_month(10, 2005)
+    assert_equal 30, Time.days_in_month(11, 2005)
+    assert_equal 31, Time.days_in_month(12, 2005)
+  end
+
+  def test_next_month_on_31st
+    assert_equal Time.local(2005, 9, 30), Time.local(2005, 8, 31).next_month
+  end
 end