Timezone at Time#+ and Time#-

* time.c (time_add): support for Timezone.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64958 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

NEWS

@@ -263,7 +263,8 @@ sufficient information, see the ChangeLog file or Redmine
     * New features:
 
         * `Time.new` and `Time#getlocal` accept a timezone object as
-	  well as UTC offset string.  [Feature #14850]
+          well as UTC offset string. `Time#+`, `Time#-` and `Time#succ`
+          also preserve the timezone.  [Feature #14850]
 
 * `TracePoint`
 

spec/ruby/core/time/plus_spec.rb

@@ -47,6 +47,19 @@ describe "Time#+" do
     (Time.new(2012, 1, 1, 0, 0, 0, 3600) + 10).utc_offset.should == 3600
   end
 
+  ruby_version_is "2.6" do
+    it "returns a time with the same timezone as self" do
+      zone = mock("timezone")
+      zone.should_receive(:local_to_utc).and_return(Time.utc(2012, 1, 1, 6, 30, 0))
+      zone.should_receive(:utc_to_local).and_return(Time.utc(2012, 1, 1, 12, 0, 10))
+      t = Time.new(2012, 1, 1, 12, 0, 0, zone) + 10
+      t.zone.should == zone
+      t.utc_offset.should == 19800
+      t.to_a[0, 6].should == [10, 0, 12, 1, 1, 2012]
+      t.should == Time.utc(2012, 1, 1, 6, 30, 10)
+    end
+  end
+
   it "does not return a subclass instance" do
     c = Class.new(Time)
     x = c.now + 1

test/ruby/test_time_tz.rb

@@ -536,4 +536,10 @@ class TestTimeTZ::WithTZ < Test::Unit::TestCase
     t = Time.new(2018, 9, 1, 12, 0, 0, tz)
     assert_equal("+0900 #{abbr}", t.strftime("%z %Z"))
   end
+
+  def test_plus_with_timezone
+    t = Time.new(2018, 9, 1, 12, 0, 0, tz) + 4000
+    assert_equal([2018, 9, 1, 13, 6, 40, tz], [t.year, t.mon, t.mday, t.hour, t.min, t.sec, t.zone])
+    assert_equal(Time.utc(2018, 9, 1, 4, 6, 40), t)
+  end
 end

time.c

@@ -3899,6 +3899,11 @@ time_add(struct time_object *tobj, VALUE torig, VALUE offset, int sign)
         GetTimeval(result, tobj);
         TZMODE_SET_FIXOFF(tobj, off);
     }
+    else if (TZMODE_LOCALTIME_P(tobj)) {
+        VALUE zone = tobj->vtm.zone;
+        GetTimeval(result, tobj);
+        tobj->vtm.zone = zone;
+    }
 
     return result;
 }
@@ -3982,6 +3987,9 @@ rb_time_succ(VALUE time)
     time = time_new_timew(rb_cTime, wadd(tobj->timew, WINT2FIXWV(TIME_SCALE)));
     GetTimeval(time, tobj2);
     TZMODE_COPY(tobj2, tobj);
+    if (TZMODE_LOCALTIME_P(tobj2) && maybe_tzobj_p(tobj2->vtm.zone)) {
+        zone_localtime(tobj2->vtm.zone, time);
+    }
     return time;
 }