Make it loose coupling between RubyGems and RDoc

lib/rdoc/rubygems_hook.rb

@@ -3,13 +3,19 @@
 require 'fileutils'
 require_relative '../rdoc'
 
-##
-# Gem::RDoc provides methods to generate RDoc and ri data for installed gems
-# upon gem installation.
+# We define the following two similar name classes in this file:
 #
-# This file is automatically required by RubyGems 1.9 and newer.
+# - RDoc::RubyGemsHook
+# - RDoc::RubygemsHook
+#
+# RDoc::RubyGemsHook is the main class that has real logic.
+#
+# RDoc::RubygemsHook is a class that is only for
+# compatibility. RDoc::RubygemsHook is used by RubyGems directly. We
+# can remove this when all maintained RubyGems remove
+# `rubygems/rdoc.rb`.
 
-class RDoc::RubygemsHook
+class RDoc::RubyGemsHook
 
   include Gem::UserInteraction
   extend  Gem::UserInteraction
@@ -45,7 +51,7 @@ class << self
   # Post installs hook that generates documentation for each specification in
   # +specs+
 
-  def self.generation_hook installer, specs
+  def self.generate installer, specs
     start = Time.now
     types = installer.document
 
@@ -64,6 +70,10 @@ def self.generation_hook installer, specs
     say "Done installing documentation for #{names} after #{duration} seconds"
   end
 
+  def self.remove uninstaller
+    new(uninstaller.spec).remove
+  end
+
   ##
   # Loads the RDoc generator
 
@@ -246,3 +256,43 @@ def setup
   end
 
 end
+
+# This class is referenced by RubyGems to create documents.
+# All implementations are moved to the above RubyGemsHook.
+#
+# This class does nothing when this RDoc is installed as a normal gem
+# or a bundled gem.
+#
+# This class does generate/remove documents for compatibility when
+# this RDoc is installed as a default gem.
+#
+# We can remove this when all maintained RubyGems remove
+# `rubygems/rdoc.rb`.
+module RDoc
+  class RubygemsHook
+    def self.default_gem?
+      !File.exist?(File.join(__dir__, "..", "rubygems_plugin.rb"))
+    end
+
+    def initialize(spec)
+      @spec = spec
+    end
+
+    def remove
+      # Do nothing if this is NOT a default gem.
+      return unless self.class.default_gem?
+
+      # Remove generated document for compatibility if this is a
+      # default gem.
+      RubyGemsHook.new(@spec).remove
+    end
+
+    def self.generation_hook installer, specs
+      # Do nothing if this is NOT a default gem.
+      return unless default_gem?
+
+      # Generate document for compatibility if this is a default gem.
+      RubyGemsHook.generate(installer, specs)
+    end
+  end
+end

lib/rubygems_plugin.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+# If this file is exist, RDoc generates and removes documents by rubygems plugins.
+#
+# In follwing cases,
+# RubyGems directly exectute RDoc::RubygemsHook.generation_hook and RDoc::RubygemsHook#remove to generate and remove documents.
+#
+# - RDoc is used as a default gem.
+# - RDoc is a old version that doesn't have rubygems_plugin.rb.
+
+require_relative 'rdoc/rubygems_hook'
+
+# To install dependency libraries of RDoc, you need to run bundle install.
+# At that time, rdoc/markdown is not generated.
+# If generate and remove are executed at that time, an error will occur.
+# So, we can't register generate and remove to Gem at that time.
+begin
+  require_relative 'rdoc/markdown'
+rescue LoadError
+else
+  Gem.done_installing(&RDoc::RubyGemsHook.method(:generate))
+  Gem.pre_uninstall(&RDoc::RubyGemsHook.method(:remove))
+end

test/rdoc/test_rdoc_rubygems_hook.rb

@@ -5,7 +5,7 @@
 require_relative '../../lib/rdoc/rubygems_hook'
 require 'test/unit'
 
-class TestRDocRubygemsHook < Test::Unit::TestCase
+class TestRDocRubyGemsHook < Test::Unit::TestCase
   def setup
     @a = Gem::Specification.new do |s|
       s.platform    = Gem::Platform::RUBY
@@ -40,10 +40,10 @@ def setup
     FileUtils.touch   File.join(@tempdir, 'a-2', 'lib', 'a.rb')
     FileUtils.touch   File.join(@tempdir, 'a-2', 'README')
 
-    @hook = RDoc::RubygemsHook.new @a
+    @hook = RDoc::RubyGemsHook.new @a
 
     begin
-      RDoc::RubygemsHook.load_rdoc
+      RDoc::RubyGemsHook.load_rdoc
     rescue Gem::DocumentError => e
       omit e.message
     end
@@ -63,7 +63,7 @@ def test_initialize
     refute @hook.generate_rdoc
     assert @hook.generate_ri
 
-    rdoc = RDoc::RubygemsHook.new @a, false, false
+    rdoc = RDoc::RubyGemsHook.new @a, false, false
 
     refute rdoc.generate_rdoc
     refute rdoc.generate_ri