handling edge case and adding documentation for String to Date/Time/D…

…ateTime conversion methods

activesupport/lib/active_support/core_ext/string/conversions.rb

@@ -2,23 +2,35 @@
 require 'active_support/core_ext/time/calculations'
 
 class String
-  # Form can be either :utc (default) or :local.
+  # Attempts to converts itself to a <tt>Time</tt> object and
+  # returns <tt>nil</tt> if it can't.
+  # <tt>form</tt> can be either :utc (default) or :local.
   def to_time(form = :utc)
     return nil if self.blank?
-    d = ::Date._parse(self, false).values_at(:year, :mon, :mday, :hour, :min, :sec, :sec_fraction, :offset).map { |arg| arg || 0 }
-    d[6] *= 1000000
-    ::Time.send("#{form}_time", *d[0..6]) - d[7]
+    parts = ::Date._parse(self, false).values_at(:year, :mon, :mday, :hour, :min, :sec, :sec_fraction, :offset)
+    return nil unless parts.any?
+    parts.map! {|part| part || 0 }
+    parts[6] *= 1000000
+    ::Time.send("#{form}_time", *parts[0..6]) - parts[7]
   end
 
+  # Attempts to converts itself to a <tt>Date</tt> object and
+  # returns <tt>nil</tt> if it can't.
   def to_date
     return nil if self.blank?
-    ::Date.new(*::Date._parse(self, false).values_at(:year, :mon, :mday))
+    parts = ::Date._parse(self, false).values_at(:year, :mon, :mday)
+    return nil unless parts.any?
+    ::Date.new(*parts)
   end
 
+  # Attempts to converts itself to a <tt>DateTime</tt> object and
+  # returns <tt>nil</tt> if it can't.
   def to_datetime
     return nil if self.blank?
-    d = ::Date._parse(self, false).values_at(:year, :mon, :mday, :hour, :min, :sec, :zone, :sec_fraction).map { |arg| arg || 0 }
-    d[5] += d.pop
-    ::DateTime.civil(*d)
+    parts = ::Date._parse(self, false).values_at(:year, :mon, :mday, :hour, :min, :sec, :zone, :sec_fraction)
+    return nil unless parts.any?
+    parts.map! {|part| part || 0 }
+    parts[5] += parts.pop
+    ::DateTime.civil(*parts)
   end
 end

activesupport/test/core_ext/string_ext_test.rb

@@ -168,6 +168,7 @@ def test_string_to_time
     assert_equal DateTime.civil(2039, 2, 27, 23, 50), "2039-02-27 23:50".to_time
     assert_equal Time.local_time(2039, 2, 27, 23, 50), "2039-02-27 23:50".to_time(:local)
     assert_equal Time.utc(2011, 2, 27, 23, 50), "2011-02-27 22:50 -0100".to_time
+    assert_nil "foo".to_time
     assert_nil "".to_time
   end
 
@@ -176,11 +177,13 @@ def test_string_to_datetime
     assert_equal 0, "2039-02-27 23:50".to_datetime.offset # use UTC offset
     assert_equal ::Date::ITALY, "2039-02-27 23:50".to_datetime.start # use Ruby's default start value
     assert_equal DateTime.civil(2039, 2, 27, 23, 50, 19 + Rational(275038, 1000000), "-04:00"), "2039-02-27T23:50:19.275038-04:00".to_datetime
+    assert_nil "foo".to_datetime
     assert_nil "".to_datetime
   end
 
   def test_string_to_date
     assert_equal Date.new(2005, 2, 27), "2005-02-27".to_date
+    assert_nil "foo".to_date
     assert_nil "".to_date
   end