Format the time string according to the precision of the time column

It is also necessary to format a time column like a datetime column.

Gemfile

@@ -87,7 +87,7 @@ platforms :ruby do
   group :db do
     gem 'pg', '>= 0.18.0'
     gem 'mysql', '>= 2.9.0'
-    gem 'mysql2', '>= 0.3.13'
+    gem 'mysql2', '>= 0.3.18'
   end
 end
 

Gemfile.lock

@@ -253,7 +253,7 @@ DEPENDENCIES
   minitest (< 5.3.4)
   mocha (~> 0.14)
   mysql (>= 2.9.0)
-  mysql2 (>= 0.3.13)
+  mysql2 (>= 0.3.18)
   nokogiri (>= 1.4.5)
   pg (>= 0.18.0)
   psych (~> 2.0)

activerecord/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Format the time string according to the precision of the time column.
+
+    *Ryuta Kamizono*
+
 *   Allow `:precision` option for time type columns.
 
     *Ryuta Kamizono*

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -75,7 +75,7 @@ module ActiveRecord
 
       def prepare_column_options(column)
         spec = super
-        spec.delete(:precision) if column.type == :datetime && column.precision == 0
+        spec.delete(:precision) if /time/ === column.sql_type && column.precision == 0
         spec
       end
 
@@ -733,7 +733,7 @@ module ActiveRecord
       end
 
       def extract_precision(sql_type)
-        if /datetime/ === sql_type
+        if /time/ === sql_type
           super || 0
         else
           super

activerecord/lib/active_record/type/date_time.rb

@@ -10,24 +10,6 @@ module ActiveRecord
         :datetime
       end
 
-      def serialize(value)
-        if precision && value.respond_to?(:usec)
-          number_of_insignificant_digits = 6 - precision
-          round_power = 10 ** number_of_insignificant_digits
-          value = value.change(usec: value.usec / round_power * round_power)
-        end
-
-        if value.acts_like?(:time)
-          zone_conversion_method = ActiveRecord::Base.default_timezone == :utc ? :getutc : :getlocal
-
-          if value.respond_to?(zone_conversion_method)
-            value = value.send(zone_conversion_method)
-          end
-        end
-
-        value
-      end
-
       private
 
       def cast_value(string)

activerecord/lib/active_record/type/helpers/time_value.rb

@@ -2,6 +2,24 @@ module ActiveRecord
   module Type
     module Helpers
       module TimeValue # :nodoc:
+        def serialize(value)
+          if precision && value.respond_to?(:usec)
+            number_of_insignificant_digits = 6 - precision
+            round_power = 10 ** number_of_insignificant_digits
+            value = value.change(usec: value.usec / round_power * round_power)
+          end
+
+          if value.acts_like?(:time)
+            zone_conversion_method = ActiveRecord::Base.default_timezone == :utc ? :getutc : :getlocal
+
+            if value.respond_to?(zone_conversion_method)
+              value = value.send(zone_conversion_method)
+            end
+          end
+
+          value
+        end
+
         def type_cast_for_schema(value)
           "'#{value.to_s(:db)}'"
         end

activerecord/test/cases/time_precision_test.rb

@@ -2,6 +2,10 @@ require 'cases/helper'
 
 if ActiveRecord::Base.connection.supports_datetime_with_precision?
 class TimePrecisionTest < ActiveRecord::TestCase
+  self.use_transactional_fixtures = false
+
+  class Foo < ActiveRecord::Base; end
+
   setup do
     @connection = ActiveRecord::Base.connection
   end
@@ -45,6 +49,21 @@ class TimePrecisionTest < ActiveRecord::TestCase
     assert_equal 4, database_datetime_precision('foos', 'finish')
   end
 
+  def test_formatting_time_according_to_precision
+    @connection.create_table(:foos, force: true) do |t|
+      t.time :start,  precision: 0
+      t.time :finish, precision: 4
+    end
+    time = ::Time.utc(2000, 1, 1, 12, 30, 0, 999999)
+    Foo.create!(start: time, finish: time)
+    assert foo = Foo.find_by(start: time)
+    assert_equal 1, Foo.where(finish: time).count
+    assert_equal time.to_s, foo.start.to_s
+    assert_equal time.to_s, foo.finish.to_s
+    assert_equal 000000, foo.start.usec
+    assert_equal 999900, foo.finish.usec
+  end
+
   private
 
   def database_datetime_precision(table_name, column_name)