Use object ids instead of hashes for Jekyll documents

.gitignore

@@ -2,3 +2,6 @@ spec/examples.txt
 *.gem
 Gemfile.lock
 /tmp
+vendor/bundle
+.bundle
+.jekyll-cache

lib/jekyll-include-cache/tag.rb

@@ -33,13 +33,35 @@ def path(context)
 
     def key(path, params)
       path_hash   = path.hash
-      params_hash = params.hash
+      params_hash = quick_hash(params)
       self.class.digest_cache[path_hash] ||= {}
       self.class.digest_cache[path_hash][params_hash] ||= digest(path_hash, params_hash)
     end
 
+    def quick_hash(params)
+      return params.hash unless params
+
+      md5 = Digest::MD5.new
+
+      params.sort.each do |_, value|
+        # Using the fact that Jekyll documents don't change during a build.
+        # Instead of calculating the hash of an entire document (expensive!)
+        # we just use its object id.
+        if value.is_a? Jekyll::Drops::Drop
+          md5.update value.object_id.to_s
+        else
+          md5.update value.hash.to_s
+        end
+      end
+
+      md5.hexdigest
+    end
+
     def digest(path_hash, params_hash)
-      Digest::MD5.hexdigest("#{path_hash}#{params_hash}")
+      md5 = Digest::MD5.new
+      md5.update path_hash.to_s
+      md5.update params_hash.to_s
+      md5.hexdigest
     end
   end
 end

spec/jekyll-include-tag/tag_spec.rb

@@ -28,21 +28,24 @@
   context "building the key" do
     it "builds the key" do
       key = subject.send(:key, "foo.html", "foo" => "bar", "foo2" => "bar2")
+      params = { "foo" => "bar", "foo2" => "bar2" }
       expect(key).to eql(
-        subject.send(:digest, "foo.html".hash, { "foo" => "bar", "foo2" => "bar2" }.hash)
+        subject.send(:digest, "foo.html".hash, subject.send(:quick_hash, params))
       )
     end
 
     it "builds the key based on the path" do
       key = subject.send(:key, "foo2.html", "foo" => "bar", "foo2" => "bar2")
+      params = { "foo" => "bar", "foo2" => "bar2" }
       expect(key).to eql(
-        subject.send(:digest, "foo2.html".hash, { "foo" => "bar", "foo2" => "bar2" }.hash)
+        subject.send(:digest, "foo2.html".hash, subject.send(:quick_hash, params))
       )
     end
 
     it "builds the key based on the params" do
       key = subject.send(:key, "foo2.html", "foo" => "bar")
-      expect(key).to eql(subject.send(:digest, "foo2.html".hash, { "foo" => "bar" }.hash))
+      params = { "foo" => "bar" }
+      expect(key).to eql(subject.send(:digest, "foo2.html".hash, subject.send(:quick_hash, params)))
     end
   end
 

spec/spec_helper.rb

@@ -21,7 +21,7 @@
 
 Jekyll.logger.adjust_verbosity(:quiet => true)
 
-Jekyll::Cache.base_dir = File.expand_path("../tmp", __dir__) if defined? Jekyll::Cache
+Jekyll::Cache.cache_dir = File.expand_path("../tmp", __dir__) if defined? Jekyll::Cache
 
 def fixture_path(fixture)
   File.expand_path "./fixtures/#{fixture}", File.dirname(__FILE__)