Added ability to compare date/time with infinity

Date, DateTime, Time and TimeWithZone can now be compared to infinity,
  so it's now possible to create ranges with one infinite bound and
  date/time object as another bound.

  Ex.: @range = Range.new(Date.today, Float::INFINITY)

Also it's possible to check inclusion of date/time in range with
  conversion.

  Ex.: @range.include?(Time.now + 1.year) # => true
       @range.include?(DateTime.now + 1.year) # => true

Ability to create date/time ranges with infinite bound is required
  for handling postgresql range types.

10 files changed, 60 insertions, 7 deletions

diff --git a/activesupport/lib/active_support/core_ext/date.rb b/activesupport/lib/active_support/core_ext/date.rb
index 465fedda80..5f13f5f70f 100644
--- a/activesupport/lib/active_support/core_ext/date.rb
+++ b/activesupport/lib/active_support/core_ext/date.rb
@@ -2,4 +2,5 @@ require 'active_support/core_ext/date/acts_like'
 require 'active_support/core_ext/date/calculations'
 require 'active_support/core_ext/date/conversions'
 require 'active_support/core_ext/date/zones'
+require 'active_support/core_ext/date/infinite_comparable'
 
diff --git a/activesupport/lib/active_support/core_ext/date/infinite_comparable.rb b/activesupport/lib/active_support/core_ext/date/infinite_comparable.rb
new file mode 100644
index 0000000000..ca5d793942
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/date/infinite_comparable.rb
@@ -0,0 +1,5 @@
+require 'active_support/core_ext/infinite_comparable'
+
+class Date
+  include InfiniteComparable
+end
diff --git a/activesupport/lib/active_support/core_ext/date_time.rb b/activesupport/lib/active_support/core_ext/date_time.rb
index e8a27b9f38..024af91738 100644
--- a/activesupport/lib/active_support/core_ext/date_time.rb
+++ b/activesupport/lib/active_support/core_ext/date_time.rb
@@ -2,3 +2,4 @@ require 'active_support/core_ext/date_time/acts_like'
 require 'active_support/core_ext/date_time/calculations'
 require 'active_support/core_ext/date_time/conversions'
 require 'active_support/core_ext/date_time/zones'
+require 'active_support/core_ext/date_time/infinite_comparable'
diff --git a/activesupport/lib/active_support/core_ext/date_time/calculations.rb b/activesupport/lib/active_support/core_ext/date_time/calculations.rb
index fca5d4d679..4e4852a5e6 100644
--- a/activesupport/lib/active_support/core_ext/date_time/calculations.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/calculations.rb
@@ -142,11 +142,4 @@ class DateTime
   def utc_offset
     (offset * 86400).to_i
   end
-
-  # Layers additional behavior on DateTime#<=> so that Time and
-  # ActiveSupport::TimeWithZone instances can be compared with a DateTime.
-  def <=>(other)
-    super other.to_datetime
-  end
-
 end
diff --git a/activesupport/lib/active_support/core_ext/date_time/infinite_comparable.rb b/activesupport/lib/active_support/core_ext/date_time/infinite_comparable.rb
new file mode 100644
index 0000000000..8a282b19f2
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/date_time/infinite_comparable.rb
@@ -0,0 +1,5 @@
+require 'active_support/core_ext/infinite_comparable'
+
+class DateTime
+  include InfiniteComparable
+end
diff --git a/activesupport/lib/active_support/core_ext/infinite_comparable.rb b/activesupport/lib/active_support/core_ext/infinite_comparable.rb
new file mode 100644
index 0000000000..a69ff6a37b
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/infinite_comparable.rb
@@ -0,0 +1,30 @@
+require 'active_support/concern'
+
+module InfiniteComparable
+  extend ActiveSupport::Concern
+
+  included do
+    alias_method_chain :<=>, :infinity
+  end
+
+  define_method '<=>_with_infinity' do |other|
+    if other.class == self.class
+      self.send(:'<=>_without_infinity', other)
+    # inf <=> inf
+    elsif other.respond_to?(:infinite?) && other.infinite? && respond_to?(:infinite?) && infinite?
+      infinite? <=> other.infinite?
+    # not_inf <=> inf
+    elsif other.respond_to?(:infinite?) && other.infinite?
+      -other.infinite?
+    # inf <=> not_inf
+    elsif respond_to?(:infinite?) && infinite?
+      infinite?
+    else
+      conversion = :"to_#{self.class.name.downcase}"
+
+      other = other.send(conversion) if other.respond_to?(conversion)
+
+      self.send(:'<=>_without_infinity', other)
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/core_ext/numeric.rb b/activesupport/lib/active_support/core_ext/numeric.rb
index a6bc0624be..d5cfc2ece4 100644
--- a/activesupport/lib/active_support/core_ext/numeric.rb
+++ b/activesupport/lib/active_support/core_ext/numeric.rb
@@ -1,3 +1,4 @@
 require 'active_support/core_ext/numeric/bytes'
 require 'active_support/core_ext/numeric/time'
 require 'active_support/core_ext/numeric/conversions'
+require 'active_support/core_ext/numeric/infinite_comparable'
diff --git a/activesupport/lib/active_support/core_ext/numeric/infinite_comparable.rb b/activesupport/lib/active_support/core_ext/numeric/infinite_comparable.rb
new file mode 100644
index 0000000000..07d4d7446a
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/numeric/infinite_comparable.rb
@@ -0,0 +1,11 @@
+require 'active_support/core_ext/big_decimal/conversions'
+require 'active_support/number_helper'
+require 'active_support/core_ext/infinite_comparable'
+
+class Float
+  include InfiniteComparable
+end
+
+class BigDecimal
+  include InfiniteComparable
+end
diff --git a/activesupport/lib/active_support/core_ext/time.rb b/activesupport/lib/active_support/core_ext/time.rb
index 32cffe237d..af6b589b71 100644
--- a/activesupport/lib/active_support/core_ext/time.rb
+++ b/activesupport/lib/active_support/core_ext/time.rb
@@ -3,3 +3,4 @@ require 'active_support/core_ext/time/calculations'
 require 'active_support/core_ext/time/conversions'
 require 'active_support/core_ext/time/marshal'
 require 'active_support/core_ext/time/zones'
+require 'active_support/core_ext/time/infinite_comparable'
diff --git a/activesupport/lib/active_support/core_ext/time/infinite_comparable.rb b/activesupport/lib/active_support/core_ext/time/infinite_comparable.rb
new file mode 100644
index 0000000000..63795885f5
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/time/infinite_comparable.rb
@@ -0,0 +1,5 @@
+require 'active_support/core_ext/infinite_comparable'
+
+class Time
+  include InfiniteComparable
+end