DateTime#<=> return nil when compare to the invalid String as Time.

before:

    p Time.now ==  'a'  # => false
    p Time.now <=> 'a'  # => nil

    require 'active_support'
    require 'active_support/core_ext'

    p Time.now ==  'a'  # => false
    p Time.now <=> 'a'  # => invalid date (ArgumentError)

and on ruby 2.2, Time.now == 'a' warning.

    warning: Comparable#== will no more rescue exceptions of #<=> in the next release.
    warning: Return nil in #<=> if the comparison is inappropriate or avoid such comparison.

after:

- Error handling.
- Quiet warnings.

1 files changed, 7 insertions, 0 deletions

diff --git a/activesupport/test/core_ext/time_ext_test.rb b/activesupport/test/core_ext/time_ext_test.rb
index d59775001b..c8364ecdff 100644
--- a/activesupport/test/core_ext/time_ext_test.rb
+++ b/activesupport/test/core_ext/time_ext_test.rb
@@ -721,6 +721,13 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal(-1, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new( Time.utc(2000, 1, 1, 0, 0, 1), ActiveSupport::TimeZone['UTC'] ))
   end
 
+  def test_compare_with_string
+    assert_equal   1, Time.utc(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59, 999).to_s
+    assert_equal   0, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0).to_s
+    assert_equal( -1, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 1, 0).to_s)
+    assert_equal nil, Time.utc(2000) <=> 'Invalid as Time'
+  end
+
   def test_at_with_datetime
     assert_equal Time.utc(2000, 1, 1, 0, 0, 0), Time.at(DateTime.civil(2000, 1, 1, 0, 0, 0))