resolves #4450 consistently produce partintro as a compound open block (PR #4451)

3 files changed, 64 insertions, 9 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 3268e598..c126bfd8 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -67,6 +67,7 @@ Improvements::
   * Don't uppercase monospace span in section title in manpage output (#4402)
   * Simplify processing of implicit link (i.e., autolink) by separating implicit and explicit match
   * Add single and double role hint to `<quote>` tag in DocBook output (#2947)
+  * Generate partintro block consistently (#4450)
 
 Bug Fixes::
 
diff --git a/lib/asciidoctor/parser.rb b/lib/asciidoctor/parser.rb
index e62a2324..2b50aa46 100644
--- a/lib/asciidoctor/parser.rb
+++ b/lib/asciidoctor/parser.rb
@@ -399,18 +399,22 @@ class Parser
           # REVIEW this may be doing too much
           if part
             if !section.blocks?
-              # if this block wasn't marked as [partintro], emulate behavior as if it had
+              # if this not a [partintro] open block, enclose it in a [partintro] open block
               if new_block.style != 'partintro'
-                # emulate [partintro] paragraph
-                if new_block.context == :paragraph
-                  new_block.context = :open
+                # if this is already a normal open block, simply add the partintro style
+                if new_block.style == 'open' && new_block.context == :open
                   new_block.style = 'partintro'
-                # emulate [partintro] open block
                 else
                   new_block.parent = (intro = Block.new section, :open, content_model: :compound)
                   intro.style = 'partintro'
                   section.blocks << intro
                 end
+              # if this is a [partintro] paragraph, convert it to a [partintro] open block w/ single paragraph
+              elsif new_block.content_model == :simple
+                new_block.content_model = :compound
+                new_block << (Block.new new_block, :paragraph, source: new_block.lines, subs: new_block.subs)
+                new_block.lines.clear
+                new_block.subs.clear
               end
             elsif section.blocks.size == 1
               first_block = section.blocks[0]
@@ -420,12 +424,11 @@ class Parser
               # rebuild [partintro] paragraph as an open block
               elsif first_block.content_model != :compound
                 new_block.parent = (intro = Block.new section, :open, content_model: :compound)
-                intro.style = 'partintro'
-                section.blocks.shift
-                if first_block.style == 'partintro'
+                if first_block.style == (intro.style = 'partintro')
                   first_block.context = :paragraph
                   first_block.style = nil
                 end
+                section.blocks.shift
                 intro << first_block
                 section.blocks << intro
               end
diff --git a/test/sections_test.rb b/test/sections_test.rb
index 6e076d93..83863424 100644
--- a/test/sections_test.rb
+++ b/test/sections_test.rb
@@ -3633,6 +3633,8 @@ context 'Sections' do
       assert_xpath '//h1[@id="_chapter_one"][text() = "Chapter One"]', output, 1
       assert_xpath '//h1[@id="_chapter_two"][text() = "Chapter Two"]', output, 1
       assert_xpath '//h1[@id="_chapter_three"][text() = "Chapter Three"]', output, 1
+      assert_css '#_chapter_one + .openblock.partintro p', output, 1
+      assert_css '#_chapter_two + .openblock.partintro p', output, 1
     end
 
     test 'should print error if level 0 section comes after nested section and doctype is not book' do
@@ -3741,7 +3743,7 @@ context 'Sections' do
 
       = Part 1
 
-      part intro
+      part intro--a summary
 
       == Chapter 1
       EOS
@@ -3749,7 +3751,53 @@ context 'Sections' do
       doc = document_from_string input
       partintro = doc.blocks.first.blocks.first
       assert_equal :open, partintro.context
+      assert_equal :compound, partintro.content_model
+      assert_empty partintro.lines
+      assert_empty partintro.subs
       assert_equal 'partintro', partintro.style
+      assert_equal :paragraph, partintro.blocks[0].context
+      assert_equal ['part intro--a summary'], partintro.blocks[0].lines
+      assert_include 'part intro&#8212;&#8203;a summary', partintro.convert
+    end
+
+    test 'should preserve title on partintro defined as partintro paragraph' do
+      input = <<~'EOS'
+      = Book
+      :doctype: book
+
+      = Part 1
+
+      .Intro
+      [partintro]
+      Read this first.
+
+      == Chapter 1
+      EOS
+
+      doc = document_from_string input
+      partintro = doc.blocks.first.blocks.first
+      assert_equal :open, partintro.context
+      assert_equal 'Intro', partintro.title
+    end
+
+    test 'should not promote title on partintro defined as normal paragraph' do
+      input = <<~'EOS'
+      = Book
+      :doctype: book
+
+      = Part 1
+
+      .Intro
+      Read this first.
+
+      == Chapter 1
+      EOS
+
+      doc = document_from_string input
+      partintro = doc.blocks.first.blocks.first
+      assert_equal :open, partintro.context
+      assert_nil partintro.title
+      assert_equal 'Intro', partintro.blocks[0].title
     end
 
     test 'should add partintro style to child open block of part' do
@@ -3769,7 +3817,9 @@ context 'Sections' do
       doc = document_from_string input
       partintro = doc.blocks.first.blocks.first
       assert_equal :open, partintro.context
+      assert_equal :compound, partintro.content_model
       assert_equal 'partintro', partintro.style
+      assert_equal :paragraph, partintro.blocks[0].context
     end
 
     test 'should wrap child paragraphs of part in partintro open block' do
@@ -3789,6 +3839,7 @@ context 'Sections' do
       doc = document_from_string input
       partintro = doc.blocks.first.blocks.first
       assert_equal :open, partintro.context
+      assert_equal :compound, partintro.content_model
       assert_equal 'partintro', partintro.style
       assert_equal 2, partintro.blocks.size
       assert_equal :paragraph, partintro.blocks[0].context