Implement group_by Liquid filter & tests.

lib/jekyll/filters.rb

@@ -100,7 +100,7 @@ def xml_escape(input)
     def cgi_escape(input)
       CGI::escape(input)
     end
-    
+
     # URI escape a string.
     #
     # input - The String to escape.
@@ -158,6 +158,31 @@ def jsonify(input)
       input.to_json
     end
 
+
+    # Group an array of items by a property
+    #
+    # input - the inputted Enumerable
+    # property - the property
+    #
+    # Returns an array of Hashes, each looking something like this:
+    #  {"name"  => "larry"
+    #   "items" => [...] } # all the items where `property` == "larry"
+    def group_by(input, property)
+      if groupable?(input)
+        input.group_by do |item|
+          if item.respond_to?(:data)
+            item.data[property.to_s].to_s
+          else
+            item[property.to_s].to_s
+          end
+        end.inject([]) do |memo, i|
+          memo << {"name" => i.first, "items" => i.last}
+        end
+      else
+        input
+      end
+    end
+
     private
     def time(input)
       case input
@@ -170,5 +195,9 @@ def time(input)
         exit(1)
       end
     end
+
+    def groupable?(element)
+      element.respond_to?(:group_by)
+    end
   end
 end

test/test_filters.rb

@@ -3,16 +3,17 @@
 class TestFilters < Test::Unit::TestCase
   class JekyllFilter
     include Jekyll::Filters
+    attr_accessor :site, :context
 
-    def initialize
-      site = Jekyll::Site.new(Jekyll.configuration({}))
-      @context = Liquid::Context.new({}, {}, { :site => site })
+    def initialize(opts = {})
+      @site = Jekyll::Site.new(Jekyll.configuration(opts))
+      @context = Liquid::Context.new({}, {}, { :site => @site })
     end
   end
 
   context "filters" do
     setup do
-      @filter = JekyllFilter.new
+      @filter = JekyllFilter.new({"source" => source_dir, "destination" => dest_dir})
       @sample_time = Time.utc(2013, 03, 27, 11, 22, 33)
       @time_as_string = "September 11, 2001 12:46:30 -0000"
     end
@@ -109,5 +110,26 @@ def initialize
         assert_equal "[{\"name\":\"Jack\"},{\"name\":\"Smith\"}]", @filter.jsonify([{:name => 'Jack'}, {:name => 'Smith'}])
       end
     end
+
+    context "group_by filter" do
+      should "successfully group array of Jekyll::Page's" do
+        @filter.site.process
+        grouping = @filter.group_by(@filter.site.pages, "layout")
+        grouping.each do |g|
+          assert ["default", "nil", ""].include?(g["name"]), "#{g['name']} isn't a valid grouping."
+          case g["name"]
+          when "default"
+            assert g["items"].is_a?(Array), "The list of grouped items for 'default' is not an Array."
+            assert_equal 3, g["items"].size
+          when "nil"
+            assert g["items"].is_a?(Array), "The list of grouped items for 'nil' is not an Array."
+            assert_equal 2, g["items"].size
+          when ""
+            assert g["items"].is_a?(Array), "The list of grouped items for '' is not an Array."
+            assert_equal 5, g["items"].size
+          end
+        end
+      end
+    end
   end
 end