Fix comment location marshalling in ClassModule

Similar to other code objects' marshalling behaviour, `ClassModule#comment_location`'s content
type would change before/after marshalling. But it should still be an array of pairs that respond
to the same set of methods.

This commit also adds documentation about the marshalling behaviour of `ClassModule#comment_location`.

Author: st0012

lib/rdoc/code_object/class_module.rb

@@ -30,7 +30,22 @@ class RDoc::ClassModule < RDoc::Context
   attr_accessor :constant_aliases
 
   ##
-  # Comment and the location it came from.  Use #add_comment to add comments
+  # An array of `[comment, location]` pairs documenting this class/module.
+  # Use #add_comment to add comments.
+  #
+  # Before marshalling:
+  # - +comment+ is a String
+  # - +location+ is an RDoc::TopLevel
+  #
+  # After unmarshalling:
+  # - +comment+ is an RDoc::Markup::Document
+  # - +location+ is a filename String
+  #
+  # These type changes are acceptable (for now) because:
+  # - +comment+: Both String and Document respond to #empty?, and #parse
+  #   returns Document as-is (see RDoc::Text#parse)
+  # - +location+: Only used by #parse to set Document#file, which accepts
+  #   both TopLevel (extracts relative_name) and String
 
   attr_accessor :comment_location
 
@@ -110,7 +125,7 @@ def initialize(name, superclass = nil)
     @is_alias_for     = nil
     @name             = name
     @superclass       = superclass
-    @comment_location = [] # [[comment, location]]
+    @comment_location = [] # Array of [comment, location] pairs
 
     super()
   end
@@ -379,10 +394,10 @@ def marshal_load(array) # :nodoc:
 
     @comment    = RDoc::Comment.from_document document
 
-    @comment_location = if RDoc::Markup::Document === document.parts.first then
-                          document
+    @comment_location = if document.parts.first.is_a?(RDoc::Markup::Document)
+                          document.parts.map { |doc| [doc, doc.file] }
                         else
-                          RDoc::Markup::Document.new document
+                          [[document, document.file]]
                         end
 
     array[5].each do |name, rw, visibility, singleton, file|

test/rdoc/code_object/class_module_test.rb

@@ -614,6 +614,44 @@ def test_marshal_load_version_3
     assert_equal tl, loaded.method_list.first.file
   end
 
+  def test_search_snippet_after_marshal
+    @store.path = Dir.tmpdir
+    tl = @store.add_file 'file.rb'
+
+    ns = tl.add_module RDoc::NormalModule, 'Namespace'
+    cm = ns.add_class RDoc::NormalClass, 'Klass', 'Super'
+    cm.add_comment 'This is a class comment', tl
+
+    loaded = Marshal.load Marshal.dump cm
+    loaded.store = @store
+
+    # Should not raise NoMethodError
+    snippet = loaded.search_snippet
+    assert_kind_of String, snippet
+    assert_match(/class comment/, snippet)
+  end
+
+  def test_comment_location_is_array_after_marshal
+    @store.path = Dir.tmpdir
+    tl = @store.add_file 'file.rb'
+
+    ns = tl.add_module RDoc::NormalModule, 'Namespace'
+    cm = ns.add_class RDoc::NormalClass, 'Klass', 'Super'
+    cm.add_comment 'This is a class comment', tl
+
+    loaded = Marshal.load Marshal.dump cm
+    loaded.store = @store
+
+    assert_kind_of Array, loaded.comment_location
+    assert_equal 1, loaded.comment_location.length
+
+    comment, location = loaded.comment_location.first
+    assert_respond_to comment, :empty?
+    assert_kind_of RDoc::Markup::Document, comment
+    # After marshal, location is the filename string (from doc.file)
+    assert_equal tl.relative_name, location
+  end
+
   def test_merge
     tl = @store.add_file 'one.rb'
     p1  = tl.add_class RDoc::NormalClass, 'Parent'
@@ -1176,12 +1214,21 @@ def test_parse_comment_location
 
     cm = Marshal.load Marshal.dump cm
 
-    doc1 = @RM::Document.new @RM::Paragraph.new 'comment 1'
-    doc1.file = tl1
-    doc2 = @RM::Document.new @RM::Paragraph.new 'comment 2'
-    doc2.file = tl2
-
-    assert_same cm.comment_location, cm.parse(cm.comment_location)
+    # After marshal, comment_location is an array of [Document, filename] pairs
+    assert_kind_of Array, cm.comment_location
+
+    # parse() should produce a proper Document from the array
+    parsed = cm.parse(cm.comment_location)
+    assert_kind_of @RM::Document, parsed
+    assert_equal 2, parsed.parts.length
+
+    # Each part should be a Document with file set
+    doc1 = parsed.parts[0]
+    doc2 = parsed.parts[1]
+    assert_kind_of @RM::Document, doc1
+    assert_kind_of @RM::Document, doc2
+    assert_equal 'one.rb', doc1.file
+    assert_equal 'two.rb', doc2.file
   end
 
   def test_remove_nodoc_children

test/rdoc/rdoc_store_test.rb

@@ -922,12 +922,15 @@ def test_save_class_merge
 
     s = RDoc::RI::Store.new(RDoc::Options.new, path: @tmpdir)
 
-    inner = @RM::Document.new @RM::Paragraph.new 'new comment'
-    inner.file = @top_level
+    loaded = s.load_class('Object')
 
-    document = @RM::Document.new inner
+    # After loading, comment_location is an array of [Document, filename] pairs
+    assert_kind_of Array, loaded.comment_location
+    assert_equal 1, loaded.comment_location.length
 
-    assert_equal document, s.load_class('Object').comment_location
+    comment, location = loaded.comment_location.first
+    assert_kind_of @RM::Document, comment
+    assert_equal @top_level.relative_name, location
   end
 
   # This is a functional test