make #inspect if zero length duration return '0 seconds' instead of e…

…mpty string [rails#2838 state:resolved]

Signed-off-by: Yehuda Katz + Carl Lerche <ykatz+clerche@engineyard.com>

activesupport/lib/active_support/duration.rb

@@ -68,10 +68,12 @@ def ago(time = ::Time.current)
 
     def inspect #:nodoc:
       consolidated = parts.inject(::Hash.new(0)) { |h,part| h[part.first] += part.last; h }
-      [:years, :months, :days, :minutes, :seconds].map do |length|
+      parts = [:years, :months, :days, :minutes, :seconds].map do |length|
         n = consolidated[length]
         "#{n} #{n == 1 ? length.to_s.singularize : length.to_s}" if n.nonzero?
-      end.compact.to_sentence(:locale => :en)
+      end.compact
+      parts = ["0 seconds"] if parts.empty?
+      parts.to_sentence(:locale => :en)
     end
 
     protected

activesupport/test/core_ext/duration_test.rb

@@ -3,6 +3,7 @@
 
 class DurationTest < ActiveSupport::TestCase
   def test_inspect
+    assert_equal '0 seconds',                       0.seconds.inspect
     assert_equal '1 month',                         1.month.inspect
     assert_equal '1 month and 1 day',               (1.month + 1.day).inspect
     assert_equal '6 months and -2 days',            (6.months - 2.days).inspect