Add fetch method to Drops

lib/jekyll/drops/drop.rb

@@ -199,6 +199,10 @@ module Jekyll
           end
         end
       end
+
+      def fetch(*args, &block)
+        to_h.fetch(*args, &block)
+      end
     end
   end
 end

test/test_drop.rb

@@ -0,0 +1,34 @@
+require "helper"
+
+class TestDrop < JekyllUnitTest
+  context "a document drop" do
+    setup do
+      @site = fixture_site({
+        "collections" => ["methods"]
+      })
+      @site.process
+      @document = @site.collections["methods"].docs.detect do |d|
+        d.relative_path == "_methods/configuration.md"
+      end
+      @drop = @document.to_liquid
+    end
+
+    should "raise KeyError if key is not found and no default provided" do
+      assert_raises KeyError do
+        @drop.fetch("not_existing_key")
+      end
+    end
+
+    should "fetch value without default" do
+      assert_equal "Jekyll.configuration", @drop.fetch("title")
+    end
+
+    should "fetch default if key is not found" do
+      assert_equal "default", @drop.fetch("not_existing_key", "default")
+    end
+
+    should "fetch default value from block if key is not found" do
+      assert_equal "default bar", @drop.fetch("bar") { |el| "default #{el}" }
+    end
+  end
+end