Add ActiveSupport::TimeZone#strptime.

This makes it easier to parse user-inputted times as from a given time zone.

activesupport/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Added `ActiveSupport::TimeZone#strptime` to allow parsing times as if
+    from a given timezone.
+
+    *Paul A Jungwirth*
+
 *   `ActiveSupport::Callbacks#skip_callback` now raises an `ArgumentError` if
     an unrecognized callback is removed.
 

activesupport/lib/active_support/values/time_zone.rb

@@ -368,6 +368,26 @@ def parse(str, now=now())
       end
     end
 
+    # Parses +str+ according to +spec+ and returns an ActiveSupport::TimeWithZone.
+    #
+    # Assumes that +str+ is a time in the time zone +self+,
+    # unless +spec+ includes an explicit time zone.
+    # (This is the same behavior as +parse+.)
+    # In either case, the returned TimeWithZone has the timezone of +self+.
+    #
+    #   Time.zone = 'Hawaii'                   # => "Hawaii"
+    #   Time.zone.strptime('1999-12-31 14:00:00', '%Y-%m-%d %H:%M:%S') # => Fri, 31 Dec 1999 14:00:00 HST -10:00
+    #
+    def strptime(str, spec)
+      case spec
+      when /(^|[^%](%%)*)%(Z|:{0,3}z)/
+        DateTime.strptime(str, spec).in_time_zone(self)
+      else
+        t = DateTime.strptime(str, spec)
+        local(t.year, t.month, t.mday, t.hour, t.min, t.sec, t.usec)
+      end
+    end
+
     # Returns an ActiveSupport::TimeWithZone instance representing the current
     # time in the time zone represented by +self+.
     #

activesupport/test/time_zone_test.rb

@@ -311,6 +311,71 @@ def test_parse_handles_dst_jump
     end
   end
 
+  def test_strptime
+    zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
+    twz = zone.strptime('1999-12-31 12:00:00', '%Y-%m-%d %H:%M:%S')
+    assert_equal Time.utc(1999,12,31,17), twz
+    assert_equal Time.utc(1999,12,31,12), twz.time
+    assert_equal Time.utc(1999,12,31,17), twz.utc
+    assert_equal zone, twz.time_zone
+  end
+
+  def test_strptime_with_nondefault_time_zone
+    with_tz_default ActiveSupport::TimeZone['Pacific Time (US & Canada)'] do
+      zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
+      twz = zone.strptime('1999-12-31 12:00:00', '%Y-%m-%d %H:%M:%S')
+      assert_equal Time.utc(1999,12,31,17), twz
+      assert_equal Time.utc(1999,12,31,12), twz.time
+      assert_equal Time.utc(1999,12,31,17), twz.utc
+      assert_equal zone, twz.time_zone
+    end
+  end
+
+  def test_strptime_with_explicit_time_zone_as_abbrev
+    zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
+    twz = zone.strptime('1999-12-31 12:00:00 PST', '%Y-%m-%d %H:%M:%S %Z')
+    assert_equal Time.utc(1999,12,31,20), twz
+    assert_equal Time.utc(1999,12,31,15), twz.time
+    assert_equal Time.utc(1999,12,31,20), twz.utc
+    assert_equal zone, twz.time_zone
+  end
+
+  def test_strptime_with_explicit_time_zone_as_h_offset
+    zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
+    twz = zone.strptime('1999-12-31 12:00:00 -08', '%Y-%m-%d %H:%M:%S %:::z')
+    assert_equal Time.utc(1999,12,31,20), twz
+    assert_equal Time.utc(1999,12,31,15), twz.time
+    assert_equal Time.utc(1999,12,31,20), twz.utc
+    assert_equal zone, twz.time_zone
+  end
+
+  def test_strptime_with_explicit_time_zone_as_hm_offset
+    zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
+    twz = zone.strptime('1999-12-31 12:00:00 -08:00', '%Y-%m-%d %H:%M:%S %:z')
+    assert_equal Time.utc(1999,12,31,20), twz
+    assert_equal Time.utc(1999,12,31,15), twz.time
+    assert_equal Time.utc(1999,12,31,20), twz.utc
+    assert_equal zone, twz.time_zone
+  end
+
+  def test_strptime_with_explicit_time_zone_as_hms_offset
+    zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
+    twz = zone.strptime('1999-12-31 12:00:00 -08:00:00', '%Y-%m-%d %H:%M:%S %::z')
+    assert_equal Time.utc(1999,12,31,20), twz
+    assert_equal Time.utc(1999,12,31,15), twz.time
+    assert_equal Time.utc(1999,12,31,20), twz.utc
+    assert_equal zone, twz.time_zone
+  end
+
+  def test_strptime_with_almost_explicit_time_zone
+    zone = ActiveSupport::TimeZone['Eastern Time (US & Canada)']
+    twz = zone.strptime('1999-12-31 12:00:00 %Z', '%Y-%m-%d %H:%M:%S %%Z')
+    assert_equal Time.utc(1999,12,31,17), twz
+    assert_equal Time.utc(1999,12,31,12), twz.time
+    assert_equal Time.utc(1999,12,31,17), twz.utc
+    assert_equal zone, twz.time_zone
+  end
+
   def test_utc_offset_lazy_loaded_from_tzinfo_when_not_passed_in_to_initialize
     tzinfo = TZInfo::Timezone.get('America/New_York')
     zone = ActiveSupport::TimeZone.create(tzinfo.name, nil, tzinfo)