resolves asciidoctor#1795 don't insert page break between part and fi…

…rst chapter if heading-part-break-after key in theme is avoid

CHANGELOG.adoc

@@ -12,6 +12,7 @@ Enhancements::
 * add `save_theme` helper to work with a copy of the theme within a scope (#2196)
 * add support for `scale` attribute or `iw` unit on `pdfwidth` attribute on image macros (#1933)
 * add backlink from bibref on bibliography entry to first reference to that entry in the document (#1737)
+* don't insert page break between part and first chapter if `heading-part-break-after` key in theme is `avoid` (#1795)
 
 == 2.0.8 (2022-06-08) - @mojavelinux
 

docs/modules/theme/pages/heading.adoc

@@ -286,7 +286,7 @@ The doctype must be `book` for the `heading-part` keys to take effect.
 |Key |Value Type |Example
 
 |break-after
-|`always` {vbar} `auto` +
+|`always` {vbar} `avoid` {vbar} `auto` +
 (default: `auto`)
 |[source]
 heading:

lib/asciidoctor/pdf/converter.rb

@@ -578,6 +578,8 @@ def prepare_theme theme
         theme.base_font_style = theme.base_font_style&.to_sym || :normal
         theme.page_numbering_start_at ||= 'body'
         theme.running_content_start_at ||= 'body'
+        theme.heading_chapter_break_before ||= 'always'
+        theme.heading_part_break_before ||= 'always'
         theme.heading_margin_page_top ||= 0
         theme.heading_margin_top ||= 0
         theme.heading_margin_bottom ||= 0
@@ -657,13 +659,14 @@ def convert_section sect, _opts = {}
         hidden = sect.option? 'notitle'
         hopts = { align: text_align, level: hlevel, part: part, chapterlike: chapterlike, outdent: !(part || chapterlike) }
         if part
-          unless @theme.heading_part_break_before == 'auto'
+          if @theme.heading_part_break_before == 'always'
             started_new = true
             start_new_part sect
           end
         elsif chapterlike
-          if @theme.heading_chapter_break_before != 'auto' ||
-              (@theme.heading_part_break_after == 'always' && sect == sect.parent.sections[0])
+          if (@theme.heading_chapter_break_before == 'always' &&
+              !(@theme.heading_part_break_after == 'avoid' && sect.first_section_of_part?)) ||
+              (@theme.heading_part_break_after == 'always' && sect.first_section_of_part?)
             started_new = true
             start_new_chapter sect
           end

lib/asciidoctor/pdf/ext/asciidoctor/section.rb

@@ -30,4 +30,8 @@ def numbered_title opts = {}
     end
     opts[:formal] ? @cached_formal_numbered_title : @cached_numbered_title
   end unless method_defined? :numbered_title
+
+  def first_section_of_part?
+    (par = @parent).context == :section && par.sectname == 'part' && self == par.blocks.find {|it| it.context == :section }
+  end unless method_defined? :first_section_of_part?
 end

spec/section_spec.rb

@@ -1185,6 +1185,24 @@
     (expect part2_text[:page_number]).to be 4
   end
 
+  it 'should not add page break after part if heading-part-break-after key in theme is avoid' do
+    pdf = to_pdf <<~'EOS', pdf_theme: { heading_part_break_after: 'avoid' }, analyze: true
+    = Document Title
+    :doctype: book
+
+    = Part I
+
+    == Chapter in Part I
+    EOS
+
+    (expect pdf.pages).to have_size 2
+    part1_text = (pdf.find_text 'Part I')[0]
+    chapter1_text = (pdf.find_text 'Chapter in Part I')[0]
+    (expect part1_text[:page_number]).to be 2
+    (expect chapter1_text[:page_number]).to be 2
+    (expect part1_text[:y] - chapter1_text[:y]).to be < 50
+  end
+
   it 'should support abstract defined as special section' do
     pdf = to_pdf <<~'EOS', analyze: true
     = Document Title