resolves asciidoctor#3693 don't break nested dlist with attached bloc…

…k if offset from parent list by empty line

CHANGELOG.adoc

@@ -74,6 +74,7 @@ Improvements::
 Bug Fixes::
 
   * Nested dlist attached using list continuation should not consume detached paragraph (#3535)
+  * Don't break nested dlist with attached block if offset from parent list by empty line (#3693)
   * Preserve paragraph breaks in normal table cell in manpage output (#4481)
   * Style cells in head row as bold in manpage output (#4490)
   * Escape spaces in include target (using inline passthrough) when generating link from include directive (#4461)

lib/asciidoctor/parser.rb

@@ -44,6 +44,12 @@ class Parser
 
   AuthorKeys = ::Set['author', 'authorinitials', 'firstname', 'middlename', 'lastname', 'email']
 
+  ListContinuationMarker = ::Module.new
+
+  ListContinuationPlaceholder = ::String.new.extend ListContinuationMarker
+
+  ListContinuationString = (::String.new LIST_CONTINUATION).extend ListContinuationMarker
+
   # Internal: A Hash mapping horizontal alignment abbreviations to alignments
   # that can be applied to a table cell (or to all cells in a column)
   TableCellHorzAlignments = {
@@ -1417,17 +1423,18 @@ def self.read_lines_for_list_item reader, list_type, sibling_trait = nil, has_te
       # the termination of the list
       break if is_sibling_list_item? this_line, list_type, sibling_trait
 
+      this_line = ListContinuationString if this_line == LIST_CONTINUATION
       prev_line = buffer.empty? ? nil : buffer[-1]
 
-      if prev_line == LIST_CONTINUATION
+      if ListContinuationMarker === prev_line
         if continuation == :inactive
           continuation = :active
           has_text = true
-          buffer[-1] = '' unless within_nested_list
+          buffer[-1] = ListContinuationPlaceholder unless within_nested_list
         end
 
         # dealing with adjacent list continuations (which is really a syntax error)
-        if this_line == LIST_CONTINUATION
+        if ListContinuationMarker === this_line
           if continuation != :frozen
             continuation = :frozen
             buffer << this_line
@@ -1507,7 +1514,7 @@ def self.read_lines_for_list_item reader, list_type, sibling_trait = nil, has_te
 
         if this_line == LIST_CONTINUATION
           detached_continuation = buffer.size
-          buffer << this_line
+          buffer << ListContinuationString
         elsif has_text # has_text only relevant for dlist, which is more greedy until it has text for an item; has_text is always true for all other lists
           # in this block, we have to see whether we stay in the list
           # TODO any way to combine this with the check after skipping blank lines?
@@ -1539,7 +1546,7 @@ def self.read_lines_for_list_item reader, list_type, sibling_trait = nil, has_te
           buffer << this_line
           has_text = true
         end
-      elsif this_line == LIST_CONTINUATION
+      elsif ListContinuationMarker === this_line
         has_text = true
         buffer << this_line
       else
@@ -1560,16 +1567,17 @@ def self.read_lines_for_list_item reader, list_type, sibling_trait = nil, has_te
 
     reader.unshift_line this_line if this_line
 
-    buffer[detached_continuation] = '' if detached_continuation
+    buffer[detached_continuation] = ListContinuationPlaceholder if detached_continuation
 
     until buffer.empty?
+      # drop optional trailing continuation
+      if ListContinuationMarker === (last_line = buffer[-1])
+        buffer.pop
+        break
       # strip trailing blank lines to prevent empty blocks
-      if (last_line = buffer[-1]).empty?
+      elsif last_line.empty?
         buffer.pop
       else
-        # drop optional trailing continuation
-        # (a blank line would have served the same purpose in the document)
-        buffer.pop if last_line == LIST_CONTINUATION
         break
       end
     end

test/lists_test.rb

@@ -3092,6 +3092,24 @@
       assert_css '.dlist .paragraph', output, 0
       assert_css '.dlist + .paragraph', output, 1
     end
+
+    test 'nested dlist with attached block offset by empty line' do
+      input = <<~'EOS'
+      category::
+
+      term 1:::
+      +
+      --
+      def 1
+      --
+      EOS
+      output = convert_string_to_embedded input
+      assert_xpath '//dl', output, 2
+      assert_xpath '//dl//dl', output, 1
+      assert_xpath '(//dl)[1]/dt[1][normalize-space(text()) = "category"]', output, 1
+      assert_xpath '(//dl)[1]//dl/dt[1][normalize-space(text()) = "term 1"]', output, 1
+      assert_xpath '(//dl)[1]//dl/dt[1]/following-sibling::dd//p[starts-with(text(), "def 1")]', output, 1
+    end
   end
 
   context 'Special lists' do