Prevent creating valid time-like objects from blank string from db

Issue #6045

activerecord/lib/active_record/connection_adapters/column.rb

@@ -158,7 +158,7 @@ module ActiveRecord
 
         def value_to_date(value)
           if value.is_a?(String)
-            return nil if value.empty?
+            return nil if value.blank?
             fast_string_to_date(value) || fallback_string_to_date(value)
           elsif value.respond_to?(:to_date)
             value.to_date
@@ -169,14 +169,14 @@ module ActiveRecord
 
         def string_to_time(string)
           return string unless string.is_a?(String)
-          return nil if string.empty?
+          return nil if string.blank?
 
           fast_string_to_time(string) || fallback_string_to_time(string)
         end
 
         def string_to_dummy_time(string)
           return string unless string.is_a?(String)
-          return nil if string.empty?
+          return nil if string.blank?
 
           string_to_time "2000-01-01 #{string}"
         end

activerecord/test/cases/column_test.rb

@@ -48,6 +48,34 @@ module ActiveRecord
           column.type_cast(false)
         end
       end
+
+      def test_type_cast_time
+        column = Column.new("field", nil, "time")
+        assert_equal nil, column.type_cast('')
+        assert_equal nil, column.type_cast('  ')
+
+        time_string = Time.now.utc.strftime("%T")
+        assert_equal time_string, column.type_cast(time_string).strftime("%T")
+      end
+
+      def test_type_cast_datetime_and_timestamp
+        [Column.new("field", nil, "datetime"), Column.new("field", nil, "timestamp")].each do |column|
+          assert_equal nil, column.type_cast('')
+          assert_equal nil, column.type_cast('  ')
+
+          datetime_string = Time.now.utc.strftime("%FT%T")
+          assert_equal datetime_string, column.type_cast(datetime_string).strftime("%FT%T")
+        end
+      end
+
+      def test_type_cast_date
+        column = Column.new("field", nil, "date")
+        assert_equal nil, column.type_cast('')
+        assert_equal nil, column.type_cast('  ')
+
+        date_string = Time.now.utc.strftime("%F")
+        assert_equal date_string, column.type_cast(date_string).strftime("%F")
+      end
     end
   end
 end