resolves asciidoctor#4024 suppress missing attribute warning when pro…

…cessing value for doctitle attribute (PR asciidoctor#4025)

suppress missing attribute warning when applying substitutions to implicit document title to assign to doctitle attribute

author should assume there's an implicit attribute entry for doctitle directly after the document title (level-0 section title)

CHANGELOG.adoc

@@ -22,6 +22,7 @@ Bug Fixes::
   * Allow showtitle/notitle to be toggled in AsciiDoc table cell if set in parent document (#4018)
   * Ensure mtime of input file honors TZ environment variable on JRuby for Windows (affects value of docdatetime attribute) (#3550)
   * Honor caption attribute on blocks that support captioned title even if corresponding *-caption document attribute is not set (#4023)
+  * Suppress missing attribute warning when applying substitutions to implicit document title to assign to doctitle attribute (#4024)
 
 Improvements::
 

lib/asciidoctor/parser.rb

@@ -144,7 +144,10 @@ def self.parse_document_header(reader, document)
         l0_section_title = nil
       else
         document.title = l0_section_title
-        doc_attrs['doctitle'] = doctitle_attr_val = document.apply_header_subs l0_section_title
+        if (doc_attrs['doctitle'] = doctitle_attr_val = document.sub_specialchars l0_section_title).include? ATTR_REF_HEAD
+          # QUESTION should we defer substituting attributes until the end of the header? or should we substitute again if necessary?
+          doc_attrs['doctitle'] = doctitle_attr_val = document.sub_attributes doctitle_attr_val, attribute_missing: 'skip'
+        end
       end
       document.header.source_location = source_location if source_location
       # default to compat-mode if document has setext doctitle

test/document_test.rb

@@ -703,16 +703,48 @@
       assert_xpath '//*[@id="preamble"]//p[text()="Override"]', doc.convert, 1
     end
 
-    test 'header substitutions should be applied to the value of the doctitle attribute' do
+    test 'should apply header substitutions to value of the doctitle attribute assigned from implicit doctitle' do
       input = <<~'EOS'
-      = <Foo> & <Bar>
+      = <Foo> {plus} <Bar>
 
       The name of the game is {doctitle}.
       EOS
 
       doc = document_from_string input
-      assert_equal '&lt;Foo&gt; &amp; &lt;Bar&gt;', (doc.attr 'doctitle')
-      assert_includes doc.blocks[0].content, '&lt;Foo&gt; &amp; &lt;Bar&gt;'
+      assert_equal '&lt;Foo&gt; &#43; &lt;Bar&gt;', (doc.attr 'doctitle')
+      assert_includes doc.blocks[0].content, '&lt;Foo&gt; &#43; &lt;Bar&gt;'
+    end
+
+    test 'should substitute attribute reference in implicit document title for attribute defined earlier in header' do
+      using_memory_logger do |logger|
+        input = <<~'EOS'
+        :project-name: ACME
+        = {project-name} Docs
+
+        {doctitle}
+        EOS
+        doc = document_from_string input, attributes: { 'attribute-missing' => 'warn' }
+        assert_empty logger
+        assert_equal 'ACME Docs', (doc.attr 'doctitle')
+        assert_equal 'ACME Docs', doc.doctitle
+        assert_xpath '//p[text()="ACME Docs"]', doc.convert, 1
+      end
+    end
+
+    test 'should not warn if implicit document title contains attribute reference for attribute defined later in header' do
+      using_memory_logger do |logger|
+        input = <<~'EOS'
+        = {project-name} Docs
+        :project-name: ACME
+
+        {doctitle}
+        EOS
+        doc = document_from_string input, attributes: { 'attribute-missing' => 'warn' }
+        assert_empty logger
+        assert_equal '{project-name} Docs', (doc.attr 'doctitle')
+        assert_equal 'ACME Docs', doc.doctitle
+        assert_xpath '//p[text()="{project-name} Docs"]', doc.convert, 1
+      end
     end
 
     test 'should recognize document title when preceded by blank lines' do