backport fix for #2430 remove null character enclosed by XML tag when…

… sanitizing text

CHANGELOG.adoc

@@ -9,6 +9,7 @@ For a detailed view of what has changed, refer to the {url-repo}/commits/main[co
 
 Bug Fixes::
 
+* remove null character enclosed in XML tag when santizing text; fixes invisible text in outline when heading contains index term (#2430)
 * alias `File.exists?` to `File.exist?` when loading RGhost optimizer to patch incompatibility when using Ruby 3.2
 
 Build / Infrastructure::

lib/asciidoctor/pdf/sanitizer.rb

@@ -19,11 +19,11 @@ module Sanitizer
         'nbsp' => ' ',
         'quot' => '"',
       }).default = '?'
-      SanitizeXMLRx = /<[^>]+>/
+      SanitizeXMLRx = /<[^>]+>\0?/
       CharRefRx = /&(?:amp;)?(?:([a-z][a-z]+\d{0,2})|#(?:(\d\d\d{0,4})|x(\h\h\h{0,3})));/
       UnescapedAmpersandRx = /&(?!(?:[a-z][a-z]+\d{0,2}|#(?:\d\d\d{0,4}|x\h\h\h{0,3}));)/
 
-      # Strip leading, trailing and repeating whitespace, remove XML tags and
+      # Strip leading, trailing and repeating whitespace, remove XML tags along with an enclosed null character, and
       # resolve all entities in the specified string.
       #
       # FIXME: move to a module so we can mix it in elsewhere

spec/outline_spec.rb

@@ -749,14 +749,18 @@
       pdf = to_pdf <<~'EOS'
       = _Document_ *Title*
       :doctype: book
+      :sectnums:
 
       == _First_ *Chapter*
+
+      == ((Wetland Birds))
       EOS
 
       outline = extract_outline pdf
-      (expect outline).to have_size 2
+      (expect outline).to have_size 3
       (expect outline[0][:title]).to eql 'Document Title'
-      (expect outline[1][:title]).to eql 'First Chapter'
+      (expect outline[1][:title]).to eql 'Chapter 1. First Chapter'
+      (expect outline[2][:title]).to eql 'Chapter 2. Wetland Birds'
     end
 
     it 'should decode character references in entries' do