Conditionally memoize certain private methods in EditLinkTag

appveyor.yml

@@ -8,13 +8,17 @@ build: off
 
 environment:
   matrix:
-    - RUBY_FOLDER_VER: "25-x64"
+    - RUBY_FOLDER_VER: "26"
+      JEKYLL_VERSION:  "3.7.0"
+    - RUBY_FOLDER_VER: "26"
+      JEKYLL_VERSION:  "4.0.0.pre.alpha1"
+    - RUBY_FOLDER_VER: "26"
     - RUBY_FOLDER_VER: "25"
     - RUBY_FOLDER_VER: "24"
     - RUBY_FOLDER_VER: "23"
 
 install:
-  - SET PATH=C:\Ruby%RUBY_FOLDER_VER%\bin;%PATH%
+  - SET PATH=C:\Ruby%RUBY_FOLDER_VER%-x64\bin;%PATH%
   - bundle install --retry 5 --jobs=%NUMBER_OF_PROCESSORS% --clean --path vendor\bundle
 
 test_script:

lib/jekyll-github-metadata/edit-link-tag.rb

@@ -69,19 +69,40 @@ def uri
       end
 
       def parts
-        @parts ||= [repository_url, "edit/", branch, source_path, page_path]
+        memoize_conditionally { [repository_url, "edit/", branch, source_path, page_path] }
       end
 
       def parts_normalized
-        @parts_normalized ||= parts.map.with_index do |part, index|
-          part = remove_leading_slash(part.to_s)
-          part = ensure_trailing_slash(part) unless index == parts.length - 1
-          ensure_not_just_a_slash(part)
+        memoize_conditionally do
+          parts.map.with_index do |part, index|
+            part = remove_leading_slash(part.to_s)
+            part = ensure_trailing_slash(part) unless index == parts.length - 1
+            ensure_not_just_a_slash(part)
+          end
         end
       end
 
       def page
-        @page ||= context.registers[:page]
+        memoize_conditionally { context.registers[:page] }
+      end
+
+      # Utility function for compatibility with Jekyll 4.0
+      def memoize_conditionally
+        if renderer_cached?
+          yield
+        else
+          dispatcher = "@#{caller_locations(1..1).first.label}".to_sym
+          if instance_variable_defined?(dispatcher)
+            instance_variable_get(dispatcher)
+          else
+            instance_variable_set(dispatcher, yield)
+          end
+        end
+      end
+
+      # Utility function to detect Jekyll 4.0
+      def renderer_cached?
+        @renderer_cached ||= context.registers[:site].liquid_renderer.respond_to?(:cache)
       end
 
       def site

spec/edit_link_tag_spec.rb

@@ -147,6 +147,21 @@
       expect(rendered).to eql("#{repository_url}/edit/#{branch}/page.md")
     end
 
+    context "is conditionally context-aware" do
+      it "returns correct URL" do
+        # create a static instance. `subject` creates a different instance on each call.
+        tag = described_class.parse(tag_name, markup, tokenizer, parse_context)
+
+        expect(tag.render(render_context)).to eql("#{repository_url}/edit/#{branch}/page.md")
+        filename = site.liquid_renderer.respond_to?(:cache) ? "dummy_page.md" : "page.md"
+        new_context = make_context(
+          :page => make_page("path" => "dummy_page.md"),
+          :site => site
+        )
+        expect(tag.render(new_context)).to eql("#{repository_url}/edit/#{branch}/#{filename}")
+      end
+    end
+
     context "when passed markup" do
       let(:markup) { '"Improve this page"' }