Add to_integer filter

lib/jekyll/filters.rb

@@ -266,7 +266,14 @@ module Jekyll
     #
     # Returns the integer value
     def to_integer(input)
-      input.to_i
+      return input if input.is_a?(Integer)
+      return 1 if input == true
+      return 0 if input == false
+      begin
+        input.to_i
+      rescue
+        raise ArgumentError, "Invalid input object type."
+      end
     end
 
     # Sort an array of objects

test/test_filters.rb

@@ -26,6 +26,7 @@ class TestFilters < JekyllUnitTest
       @sample_date = Date.parse("2013-03-27")
       @time_as_string = "September 11, 2001 12:46:30 -0000"
       @time_as_numeric = 1_399_680_607
+      @integer_as_string = "142857"
       @array_of_objects = [
         { "color" => "red",  "size" => "large"  },
         { "color" => "red",  "size" => "medium" },
@@ -235,6 +236,13 @@ class TestFilters < JekyllUnitTest
             @filter.date_to_rfc822(@time_as_string)
           )
         end
+
+        should "convert a String to Integer" do
+          assert_equal(
+            142857,
+            @filter.to_integer(@integer_as_string)
+          )
+        end
       end
 
       context "with a Numeric object" do
@@ -635,6 +643,30 @@ class TestFilters < JekyllUnitTest
       end
     end
 
+    context "to_integer filter" do
+      should "raise Exception when input is not integer or string" do
+        err_msg = "Invalid input object type."
+        err = assert_raises ArgumentError do
+          @filter.to_integer([1, 2])
+        end
+        assert_equal err_msg, err.message
+      end
+      should "return 0 when input is nil" do
+        assert_equal 0, @filter.to_integer(nil)
+      end
+      should "return integer when input is boolean" do
+        assert_equal 0, @filter.to_integer(false)
+        assert_equal 1, @filter.to_integer(true)
+      end
+      should "return integers" do
+        assert_equal 0, @filter.to_integer(0)
+        assert_equal 1, @filter.to_integer(1)
+        assert_equal 1, @filter.to_integer(1.42857)
+        assert_equal -1, @filter.to_integer(-1)
+        assert_equal -1, @filter.to_integer(-1.42857)
+      end
+    end
+
     context "inspect filter" do
       should "return a HTML-escaped string representation of an object" do
         assert_equal "{&quot;&lt;a&gt;&quot;=&gt;1}", @filter.inspect({ "<a>" => 1 })