change Block#content to return empty string instead of nil if raw or verbatim block has no lines

* makes return value type consistent

5 files changed, 26 insertions, 13 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 3a8f7254..0e4ccb45 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -60,6 +60,7 @@ Improvements::
   * Remove form styles from the default stylesheet (#4186)
   * Set linenums option on source block when line numbering is enabled (#3313)
   * Warn if include target is remote and `allow-uri-read` attribute is not set (#2284)
+  * Return empty string instead of nil if raw or verbatim block has no lines
 
 Bug Fixes::
 
diff --git a/lib/asciidoctor/block.rb b/lib/asciidoctor/block.rb
index a1bf00cc..ecd2a1bd 100644
--- a/lib/asciidoctor/block.rb
+++ b/lib/asciidoctor/block.rb
@@ -116,7 +116,7 @@ class Block < AbstractBlock
       # maybe apply_subs can know how to strip whitespace?
       result = apply_subs @lines, @subs
       if result.size < 2
-        result[0]
+        result[0] || ''
       else
         result.shift while (first = result[0]) && first.rstrip.empty?
         result.pop while (last = result[-1]) && last.rstrip.empty?
diff --git a/lib/asciidoctor/converter/docbook5.rb b/lib/asciidoctor/converter/docbook5.rb
index 30fad2d1..4ae11127 100644
--- a/lib/asciidoctor/converter/docbook5.rb
+++ b/lib/asciidoctor/converter/docbook5.rb
@@ -250,10 +250,10 @@ class Converter::DocBook5Converter < Converter::Base
   def convert_stem node
     if (idx = node.subs.index :specialcharacters)
       node.subs.delete_at idx
-      equation = node.content || ''
+      equation = node.content
       idx > 0 ? (node.subs.insert idx, :specialcharacters) : (node.subs.unshift :specialcharacters)
     else
-      equation = node.content || ''
+      equation = node.content
     end
     if node.style == 'asciimath'
       # NOTE fop requires jeuclid to process mathml markup
diff --git a/lib/asciidoctor/converter/html5.rb b/lib/asciidoctor/converter/html5.rb
index 46efb92e..0c0b6362 100644
--- a/lib/asciidoctor/converter/html5.rb
+++ b/lib/asciidoctor/converter/html5.rb
@@ -678,7 +678,7 @@ Your browser does not support the audio tag.
     title_element = node.title? ? %(<div class="title">#{node.captioned_title}</div>\n) : ''
     %(<div#{id_attribute} class="listingblock#{(role = node.role) ? " #{role}" : ''}">
 #{title_element}<div class="content">
-#{syntax_hl ? (syntax_hl.format node, lang, opts) : pre_open + (node.content || '') + pre_close}
+#{syntax_hl ? (syntax_hl.format node, lang, opts) : pre_open + node.content + pre_close}
 </div>
 </div>)
   end
diff --git a/test/blocks_test.rb b/test/blocks_test.rb
index ccb15e1e..ba6182f7 100644
--- a/test/blocks_test.rb
+++ b/test/blocks_test.rb
@@ -1105,14 +1105,19 @@ context 'Blocks' do
       assert_message @logger, :WARN, '<stdin>: line 3: unterminated listing block', Hash
     end
 
-    test 'should not crash if listing block has no lines' do
-      input = <<~'EOS'
-      ----
-      ----
-      EOS
-      output = convert_string_to_embedded input
-      assert_css 'pre', output, 1
-      assert_css 'pre:empty', output, 1
+    test 'should not crash when converting verbatim block that has no lines' do
+      [%(----\n----), %(....\n....)].each do |input|
+        output = convert_string_to_embedded input
+        assert_css 'pre', output, 1
+        assert_css 'pre:empty', output, 1
+      end
+    end
+
+    test 'should return content as empty string for verbatim or raw block that has no lines' do
+      [%(----\n----), %(....\n....)].each do |input|
+        doc = document_from_string input
+        assert_equal '', doc.blocks[0].content
+      end
     end
 
     test 'should preserve newlines in literal block' do
@@ -1848,7 +1853,7 @@ context 'Blocks' do
   end
 
   context 'Math blocks' do
-    test 'should not crash when converting to HTML if stem block is empty' do
+    test 'should not crash when converting stem block that has no lines' do
       input = <<~'EOS'
       [stem]
       ++++
@@ -1859,6 +1864,13 @@ context 'Blocks' do
       assert_css '.stemblock', output, 1
     end
 
+    test 'should return content as empty string for stem or pass block that has no lines' do
+      [%(++++\n++++), %([stem]\n++++\n++++)].each do |input|
+        doc = document_from_string input
+        assert_equal '', doc.blocks[0].content
+      end
+    end
+
     test 'should add LaTeX math delimiters around latexmath block content' do
       input = <<~'EOS'
       [latexmath]