url: fix issue with bad URL escaping when using Drop

lib/jekyll/url.rb

@@ -79,8 +79,12 @@ module Jekyll
     end
 
     def generate_url_from_drop(template)
-      template.gsub(/(:[a-z_]+)/) do |match|
+      template.gsub(/:([a-z_]+)/) do |match|
-        @placeholders.public_send(match.sub(':', ''))
+        if replacement = @placeholders.public_send(match.sub(':', ''))
+          self.class.escape_path replacement
+        else
+          ''.freeze
+        end
       end.gsub(/\/\//, '/')
     end
 

lib/jekyll/utils.rb

@@ -174,13 +174,14 @@ module Jekyll
         SLUGIFY_PRETTY_REGEXP
       end
 
-      slug = string.
+      # Strip according to the mode
-        # Strip according to the mode
+      slug = string.gsub(re, '-')
-        gsub(re, '-').
-        # Remove leading/trailing hyphen
-        gsub(/^\-|\-$/i, '')
 
-      cased ? slug : slug.downcase
+      # Remove leading/trailing hyphen
+      slug.gsub!(/^\-|\-$/i, '')
+
+      slug.downcase! unless cased
+      slug
     end
 
     # Add an appropriate suffix to template so that it matches the specified

test/test_url.rb

@@ -54,5 +54,23 @@ class TestURL < JekyllUnitTest
       ).to_s
     end
 
+    should "handle UrlDrop as a placeholder in addition to a hash" do
+      site = fixture_site({
+        "collections" => {
+          "methods" => {
+            "output" => true
+          }
+        },
+      })
+      site.read
+      doc = site.collections["methods"].docs.find do |doc|
+        doc.relative_path == "_methods/escape-+ #%20[].md"
+      end
+      assert_equal '/methods/escape-+-20/escape-20.html', URL.new(
+        :template => '/methods/:title/:name:output_ext',
+        :placeholders => doc.url_placeholders
+      ).to_s
+    end
+
   end
 end