Stop generating a separate page file for main_page

When a page is used as main_page (e.g. README.md), its content is
already displayed on index.html. Generating a separate page file
(e.g. README_md.html) is redundant.

Skip the main_page in:
- darkfish generator (page file generation)
- json search index (avoids linking to a nonexistent page)
- aliki sidebar pages template

Author: st0012

lib/rdoc/generator/darkfish.rb

@@ -393,6 +393,8 @@ def generate_file_files
     @files.each do |file|
       current = file
 
+      next if file.full_name == @options.main_page
+
       if file.text? and page_file.exist? then
         generate_page file
         next

lib/rdoc/generator/json_index.rb

@@ -250,7 +250,7 @@ def index_pages
     debug_msg "  generating pages search index"
 
     pages = @files.select do |file|
-      file.text?
+      file.text? && file.full_name != @options.main_page
     end
 
     pages.each do |page|

lib/rdoc/generator/template/aliki/_sidebar_pages.rhtml

@@ -1,4 +1,4 @@
-<%- simple_files = @files.select { |f| f.text? } %>
+<%- simple_files = @files.select { |f| f.text? && f.full_name != @options.main_page } %>
 
 <%- if defined?(current) && current.respond_to?(:page_name) %>
   <%- dir = current.full_name[%r{\A[^/]+(?=/)}] || current.page_name %>

test/rdoc/generator/darkfish_test.rb

@@ -178,6 +178,22 @@ def test_generate_index_with_main_page
     assert_not_include index_html, 'This is the API documentation for My awesome Ruby project.'
   end
 
+  def test_generate_does_not_create_page_file_for_main_page
+    top_level = @store.add_file("README.rdoc", parser: RDoc::Parser::Simple)
+    top_level.comment = "= Main Page\nThis is the main page content."
+
+    other_page = @store.add_file("OTHER.rdoc", parser: RDoc::Parser::Simple)
+    other_page.comment = "= Other Page\nThis is another page."
+
+    @options.main_page = "README.rdoc"
+
+    @g.generate
+
+    assert_file "index.html"
+    refute File.exist?("README_rdoc.html"), "main_page should not be generated as a separate page"
+    assert_file "OTHER_rdoc.html"
+  end
+
   def test_generate_index_without_main_page
     top_level = @store.add_file 'file.rb'
     top_level.comment = <<~RDOC