Add to_integer filter

Add to_integer filter

Fix test_filter: parenthesize the method

Fix offense: seperate every 3 digits with _

rubocop:disable Metrics/ModuleLength

More descriptive exception

Fix fmt error

Remove if stmt for integer input

Remove rescue for to_i

Remove error message assert

lib/jekyll/filters.rb

@@ -260,6 +260,17 @@ module Jekyll
       end
     end
 
+    # Convert the input into integer
+    #
+    # input - the object string
+    #
+    # Returns the integer value
+    def to_integer(input)
+      return 1 if input == true
+      return 0 if input == false
+      input.to_i
+    end
+
     # Sort an array of objects
     #
     # input - the object array

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(
+            142_857,
+            @filter.to_integer(@integer_as_string)
+          )
+        end
       end
 
       context "with a Numeric object" do
@@ -635,6 +643,28 @@ class TestFilters < JekyllUnitTest
       end
     end
 
+    context "to_integer filter" do
+      should "raise Exception when input is not integer or string" do
+        assert_raises NoMethodError do
+          @filter.to_integer([1, 2])
+        end
+      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 })