Memoize array of drop getter method names (#8421)

Merge pull request 8421

lib/jekyll/drops/drop.rb

@@ -6,6 +6,8 @@ module Jekyll
       include Enumerable
 
       NON_CONTENT_METHODS = [:fallback_data, :collapse_document].freeze
+      NON_CONTENT_METHOD_NAMES = NON_CONTENT_METHODS.map(&:to_s).freeze
+      private_constant :NON_CONTENT_METHOD_NAMES
 
       # A private stash to avoid repeatedly generating the setter method name string for
       # a call to `Drops::Drop#[]=`.
@@ -88,6 +90,17 @@ module Jekyll
         def data_delegator(key)
           define_method(key.to_sym) { @obj.data[key] }
         end
+
+        # Array of stringified instance methods that do not end with the assignment operator.
+        #
+        # (<klass>.instance_methods always generates a new Array object so it can be mutated)
+        #
+        # Returns array of strings.
+        def getter_method_names
+          @getter_method_names ||= instance_methods.map!(&:to_s).tap do |list|
+            list.reject! { |item| item.end_with?("=") }
+          end
+        end
       end
 
       # Create a new Drop
@@ -152,9 +165,10 @@ module Jekyll
       #
       # Returns an Array of strings which represent method-specific keys.
       def content_methods
-        @content_methods ||= (
+        @content_methods ||= \
-          self.class.instance_methods - Jekyll::Drops::Drop.instance_methods - NON_CONTENT_METHODS
+          self.class.getter_method_names \
-        ).map!(&:to_s).tap { |result| result.reject! { |method| method.end_with?("=") } }
+            - Jekyll::Drops::Drop.getter_method_names \
+            - NON_CONTENT_METHOD_NAMES
       end
 
       # Check if key exists in Drop

test/test_drop.rb

@@ -5,6 +5,8 @@ require "helper"
 class DropFixture < Jekyll::Drops::Drop
   mutable true
 
+  attr_accessor :lipsum
+
   def foo
     "bar"
   end
@@ -40,6 +42,39 @@ class TestDrop < JekyllUnitTest
       assert_equal "bar", @drop.invoke_drop("foo")
     end
 
+    should "return array of strings for .getter_methods" do
+      assert(@drop.class.getter_method_names.all? { |entry| entry.is_a?(String) })
+    end
+
+    should "return array of only getter method name strings for .getter_methods" do
+      [:lipsum, :lipsum=].each { |id| assert_includes(@drop.class.instance_methods, id) }
+
+      assert_includes @drop.class.getter_method_names, "lipsum"
+      refute_includes @drop.class.getter_method_names, "lipsum="
+    end
+
+    should "not munge results for another Jekyll::Drops::Drop subclass" do
+      fixture_ids = [:lipsum, :lipsum=, :foo]
+      fixture_getter_names = %w(lipsum foo)
+      fixture_ids.each { |id| assert_includes(@drop.class.instance_methods, id) }
+
+      fixture_getter_names.each do |name|
+        assert_includes @drop.class.getter_method_names, name
+        refute_includes @document_drop.class.getter_method_names, name
+      end
+    end
+
+    should "return only getter method names for #content_methods" do
+      drop_base_class_method_names = Jekyll::Drops::Drop.instance_methods.map(&:to_s)
+      sample_method_names = ["lipsum=", "fallback_data", "collapse_document"]
+
+      (sample_method_names + drop_base_class_method_names).each do |entry|
+        refute_includes @drop.content_methods, entry
+      end
+
+      assert_equal %w(foo lipsum), @drop.content_methods.sort
+    end
+
     context "mutations" do
       should "return mutations for #[]" do
         @drop["foo"] = "baz"