8 files changed, 45 insertions, 13 deletions
diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 0f9399f4d6..1863eec947 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   Add `DateTime#usec` and `DateTime#nsec` so that `ActiveSupport::TimeWithZone` keeps
+    sub-second resolution when wrapping a `DateTime` value.
+    Fixes #10855
+
+    *Andrew White*
+
 *   Fix `ActiveSupport::Dependencies::Loadable#load_dependency` calling
     `#blame_file!` on Exceptions that do not have the Blamable mixin
 
diff --git a/activesupport/lib/active_support/backtrace_cleaner.rb b/activesupport/lib/active_support/backtrace_cleaner.rb
index 4b41e6247d..6f9dc679c2 100644
--- a/activesupport/lib/active_support/backtrace_cleaner.rb
+++ b/activesupport/lib/active_support/backtrace_cleaner.rb
@@ -13,17 +13,17 @@ module ActiveSupport
   # can focus on the rest.
   #
   #   bc = BacktraceCleaner.new
-  #   bc.add_filter   { |line| line.gsub(Rails.root, '') }
-  #   bc.add_silencer { |line| line =~ /mongrel|rubygems/ }
-  #   bc.clean(exception.backtrace) # will strip the Rails.root prefix and skip any lines from mongrel or rubygems
+  #   bc.add_filter   { |line| line.gsub(Rails.root, '') } # strip the Rails.root prefix
+  #   bc.add_silencer { |line| line =~ /mongrel|rubygems/ } # skip any lines from mongrel or rubygems
+  #   bc.clean(exception.backtrace) # perform the cleanup
   #
   # To reconfigure an existing BacktraceCleaner (like the default one in Rails)
   # and show as much data as possible, you can always call
   # <tt>BacktraceCleaner#remove_silencers!</tt>, which will restore the
   # backtrace to a pristine state. If you need to reconfigure an existing
   # BacktraceCleaner so that it does not filter or modify the paths of any lines
-  # of the backtrace, you can call BacktraceCleaner#remove_filters! These two
-  # methods will give you a completely untouched backtrace.
+  # of the backtrace, you can call <tt>BacktraceCleaner#remove_filters!<tt>
+  # These two methods will give you a completely untouched backtrace.
   #
   # Inspired by the Quiet Backtrace gem by Thoughtbot.
   class BacktraceCleaner
diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index b1ab5570a8..c539048a85 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -228,7 +228,7 @@ module ActiveSupport
       #
       # Setting <tt>:race_condition_ttl</tt> is very useful in situations where
       # a cache entry is used very frequently and is under heavy load. If a
-      # cache expires and due to heavy load seven different processes will try
+      # cache expires and due to heavy load several different processes will try
       # to read data natively and then they all will try to write to cache. To
       # avoid that case the first process to find an expired cache entry will
       # bump the cache expiration time by the value set in <tt>:race_condition_ttl</tt>.
diff --git a/activesupport/lib/active_support/core_ext/date_time/conversions.rb b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
index df07917d19..c44626aed9 100644
--- a/activesupport/lib/active_support/core_ext/date_time/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/date_time/conversions.rb
@@ -80,6 +80,16 @@ class DateTime
     seconds_since_unix_epoch.to_i
   end
 
+  # Returns the fraction of a second as microseconds
+  def usec
+    (sec_fraction * 1_000_000).to_i
+  end
+
+  # Returns the fraction of a second as nanoseconds
+  def nsec
+    (sec_fraction * 1_000_000_000).to_i
+  end
+
   private
 
   def offset_in_seconds
diff --git a/activesupport/lib/active_support/notifications.rb b/activesupport/lib/active_support/notifications.rb
index c45358bba9..b32aa75e59 100644
--- a/activesupport/lib/active_support/notifications.rb
+++ b/activesupport/lib/active_support/notifications.rb
@@ -143,8 +143,8 @@ module ActiveSupport
   #
   # == Default Queue
   #
-  # Notifications ships with a queue implementation that consumes and publish events
-  # to log subscribers in a thread. You can use any queue implementation you want.
+  # Notifications ships with a queue implementation that consumes and publishes events
+  # to all log subscribers. You can use any queue implementation you want.
   #
   module Notifications
     class << self
diff --git a/activesupport/lib/active_support/time_with_zone.rb b/activesupport/lib/active_support/time_with_zone.rb
index 4a032b0ad0..95b9b8e5ae 100644
--- a/activesupport/lib/active_support/time_with_zone.rb
+++ b/activesupport/lib/active_support/time_with_zone.rb
@@ -292,7 +292,7 @@ module ActiveSupport
       end
     end
 
-    %w(year mon month day mday wday yday hour min sec to_date).each do |method_name|
+    %w(year mon month day mday wday yday hour min sec usec nsec to_date).each do |method_name|
       class_eval <<-EOV, __FILE__, __LINE__ + 1
         def #{method_name}    # def month
           time.#{method_name} #   time.month
@@ -300,10 +300,6 @@ module ActiveSupport
       EOV
     end
 
-    def usec
-      time.respond_to?(:usec) ? time.usec : 0
-    end
-
     def to_a
       [time.sec, time.min, time.hour, time.day, time.mon, time.year, time.wday, time.yday, dst?, zone]
     end
diff --git a/activesupport/test/core_ext/date_time_ext_test.rb b/activesupport/test/core_ext/date_time_ext_test.rb
index 3e76b8a9b1..571344b728 100644
--- a/activesupport/test/core_ext/date_time_ext_test.rb
+++ b/activesupport/test/core_ext/date_time_ext_test.rb
@@ -327,6 +327,16 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
     assert_equal 946684800, DateTime.civil(1999,12,31,19,0,0,Rational(-5,24)).to_i
   end
 
+  def test_usec
+    assert_equal 0, DateTime.civil(2000).usec
+    assert_equal 500000, DateTime.civil(2000, 1, 1, 0, 0, Rational(1,2)).usec
+  end
+
+  def test_nsec
+    assert_equal 0, DateTime.civil(2000).nsec
+    assert_equal 500000000, DateTime.civil(2000, 1, 1, 0, 0, Rational(1,2)).nsec
+  end
+
   protected
     def with_env_tz(new_tz = 'US/Eastern')
       old_tz, ENV['TZ'] = ENV['TZ'], new_tz
diff --git a/activesupport/test/core_ext/time_with_zone_test.rb b/activesupport/test/core_ext/time_with_zone_test.rb
index 3ce3297874..ddcfcc491f 100644
--- a/activesupport/test/core_ext/time_with_zone_test.rb
+++ b/activesupport/test/core_ext/time_with_zone_test.rb
@@ -445,6 +445,16 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     assert_equal 0, twz.usec
   end
 
+  def test_usec_returns_sec_fraction_when_datetime_is_wrapped
+    twz = ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 1, 0, 0, Rational(1,2)), @time_zone)
+    assert_equal 500000, twz.usec
+  end
+
+  def test_nsec_returns_sec_fraction_when_datetime_is_wrapped
+    twz = ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 1, 0, 0, Rational(1,2)), @time_zone)
+    assert_equal 500000000, twz.nsec
+  end
+
   def test_utc_to_local_conversion_saves_period_in_instance_variable
     assert_nil @twz.instance_variable_get('@period')
     @twz.time