logger: fix monthly log rotate with DST

* lib/logger.rb (Logger::Period#next_rotate_time): fix monthly log
  rotate when DST is applied during a month of 31 days.
  [Fix GH-1458]

With DST the month of october can actually last more than 31 days.
It can last 31 days plus 1 hour. So during october, `t` used to be
equal to "2016-10-31 23:00:00" instead of "2016-11-01 00:00:00".
This was then normalized to "2016-10-01 00:00:00" which lead every
single line of log during october to rotate the log file.
This fix ensure that next_rotate_time(now, 'monthly') always return
the first day of next month in every situation.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56374 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Sat Oct  8 09:06:55 2016  Aurelien Jacobs  <aurel@gnuage.org>
+
+	* lib/logger.rb (Logger::Period#next_rotate_time): fix monthly log
+	  rotate when DST is applied during a month of 31 days.
+	  [Fix GH-1458]
+
 Fri Oct  7 20:21:39 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* gc.c (gc_prof_setup_new_record): fix the condition to get

lib/logger.rb

@@ -629,8 +629,8 @@ private
       when 'weekly'
         t = Time.mktime(now.year, now.month, now.mday) + SiD * (7 - now.wday)
       when 'monthly'
-        t = Time.mktime(now.year, now.month, 1) + SiD * 31
-        return Time.mktime(t.year, t.month, 1) if t.mday > 1
+        t = Time.mktime(now.year, now.month, 1) + SiD * 32
+        return Time.mktime(t.year, t.month, 1)
       else
         return now
       end

test/logger/test_logdevice.rb

@@ -512,6 +512,49 @@ class TestLogDevice < Test::Unit::TestCase
     end
   end if env_tz_works
 
+  def test_shifting_monthly
+    Dir.mktmpdir do |tmpdir|
+      assert_in_out_err([{"TZ"=>"UTC"}, *%W"-rlogger -C#{tmpdir} -"], <<-'end;')
+        begin
+          module FakeTime
+            attr_accessor :now
+          end
+
+          class << Time
+            prepend FakeTime
+          end
+
+          log = "log"
+          File.open(log, "w") {}
+
+          Time.now = Time.utc(2015, 12, 14, 0, 1, 1)
+          dev = Logger::LogDevice.new("log", shift_age: 'monthly')
+
+          Time.now = Time.utc(2015, 12, 31, 12, 34, 56)
+          dev.write("#{Time.now} hello-1\n")
+          File.utime(Time.now, Time.now, log)
+
+          Time.now = Time.utc(2016, 1, 1, 0, 1, 1)
+          File.utime(Time.now, Time.now, log)
+          dev.write("#{Time.now} hello-2\n")
+        ensure
+          dev.close if dev
+        end
+      end;
+      log = File.join(tmpdir, "log")
+      cont = File.read(log)
+      assert_match(/hello-2/, cont)
+      assert_not_match(/hello-1/, cont)
+      log = Dir.glob(log+".*")
+      assert_equal(1, log.size)
+      log, = *log
+      cont = File.read(log)
+      assert_match(/hello-1/, cont)
+      assert_equal("2015-12-31", cont[/^[-\d]+/])
+      assert_equal("20151231", log[/\d+\z/])
+    end
+  end if env_tz_works
+
   def test_shifting_dst_change
     Dir.mktmpdir do |tmpdir|
       assert_in_out_err([{"TZ"=>"Europe/London"}, *%W"--disable=gems -rlogger -C#{tmpdir} -"], <<-'end;')
@@ -578,6 +621,53 @@ class TestLogDevice < Test::Unit::TestCase
     end
   end if env_tz_works
 
+  def test_shifting_monthly_dst_change
+    Dir.mktmpdir do |tmpdir|
+      assert_separately([{"TZ"=>"Europe/London"}, *%W"-rlogger -C#{tmpdir} -"], <<-'end;')
+        begin
+          module FakeTime
+            attr_accessor :now
+          end
+
+          class << Time
+            prepend FakeTime
+          end
+
+          log = "log"
+          File.open(log, "w") {}
+
+          Time.now = Time.utc(2016, 9, 1, 0, 1, 1)
+          dev = Logger::LogDevice.new("log", shift_age: 'monthly')
+
+          Time.now = Time.utc(2016, 9, 8, 7, 6, 5)
+          dev.write("#{Time.now} hello-1\n")
+          File.utime(Time.now, Time.now, log)
+
+          Time.now = Time.utc(2016, 10, 9, 8, 7, 6)
+          File.utime(Time.now, Time.now, log)
+          dev.write("#{Time.now} hello-2\n")
+
+          Time.now = Time.utc(2016, 10, 9, 8, 7, 7)
+          File.utime(Time.now, Time.now, log)
+          dev.write("#{Time.now} hello-3\n")
+        ensure
+          dev.close if dev
+        end
+      end;
+      log = File.join(tmpdir, "log")
+      cont = File.read(log)
+      assert_match(/hello-2/, cont)
+      assert_not_match(/hello-1/, cont)
+      log = Dir.glob(log+".*")
+      assert_equal(1, log.size)
+      log, = *log
+      cont = File.read(log)
+      assert_match(/hello-1/, cont)
+      assert_equal("2016-09-08", cont[/^[-\d]+/])
+      assert_equal("20160930", log[/\d+\z/])
+    end
+  end if env_tz_works
+
   private
 
   def run_children(n, args, src)