Add RDoc coverage check for C extensions in ruby-core CI

.github/workflows/ruby-core.yml

@@ -69,6 +69,14 @@ jobs:
       - name: Generate Documentation with RDoc
         run: make html
         working-directory: ruby/ruby
+      - name: Core docs coverage
+        # Exclusions match RDOC_COVERAGE_EXCLUDES in ruby/ruby's common.mk.
+        # Run after make html so the build environment is fully set up
+        # (rbconfig.rb, generated files, etc.), matching ruby/ruby's CI.
+        run: >
+          make XRUBY=ruby RDOC_DEPENDS= RBCONFIG=update-rbconfig
+          rdoc-coverage
+        working-directory: ruby/ruby
       # We need to clear the generated documentation to generate them again
       # with the Ripper parser.
       - name: Clear Generated Documentation

lib/rdoc/code_object.rb

@@ -125,6 +125,7 @@ def initialize_visibility # :nodoc:
     @received_nodoc      = false
     @ignored             = false
     @suppressed          = false
+    @stopped_doc         = false
     @track_visibility    = true
   end
 
@@ -205,7 +206,7 @@ def documented?
   def done_documenting=(value)
     return unless @track_visibility
     @done_documenting  = value
-    @document_self     = !value
+    @document_self     = !value unless @stopped_doc
     @document_children = @document_self
   end
 
@@ -343,6 +344,7 @@ def start_doc
     @document_children = true
     @ignored    = false
     @suppressed = false
+    @stopped_doc = false
   end
 
   ##

lib/rdoc/markup/pre_process.rb

@@ -232,6 +232,7 @@ def handle_directive(prefix, directive, param, code_object = nil,
       return blankline unless code_object
 
       code_object.stop_doc
+      code_object.instance_variable_set(:@stopped_doc, true)
 
       blankline
     when 'yield', 'yields' then

test/rdoc/rdoc_rdoc_test.rb

@@ -358,6 +358,30 @@ def test_parse_file_encoding
     tf.close!
   end
 
+  def test_parse_file_stopdoc_in_c
+    @rdoc.store = RDoc::Store.new(@options)
+
+    temp_dir do |dir|
+      @rdoc.options.root = Pathname(Dir.pwd)
+
+      File.write 'test.c', <<~C
+        void Init_test(void) {
+            VALUE rb_cParent = rb_define_class("Parent", rb_cObject);
+
+            /* :stopdoc: */
+            VALUE cInternal = rb_define_class_under(rb_cParent, "Internal", rb_cObject);
+            /* :startdoc: */
+        }
+      C
+
+      top_level = @rdoc.parse_file 'test.c'
+
+      internal = @rdoc.store.find_class_named 'Parent::Internal'
+      assert internal, 'Parent::Internal should exist'
+      refute internal.document_self, 'Parent::Internal should have document_self=false after :stopdoc:'
+    end
+  end
+
   def test_parse_file_forbidden
     omit 'chmod not supported' if Gem.win_platform?
     omit "assumes that euid is not root" if Process.euid == 0