resolves asciidoctor#4368 redo loop rather than using recursion to lo…

…cate next line to process

CHANGELOG.adoc

@@ -57,6 +57,10 @@ Improvements::
   * 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)
 
+Bug Fixes::
+
+  * Redo loop rather than using recursion to locate next line to process; prevents stack limit error (#4368)
+
 == 2.0.18 (2022-10-15) - @mojavelinux
 
 Improvements::

lib/asciidoctor/reader.rb

@@ -129,16 +129,16 @@ def next_line_empty?
   # Returns the next line of the source data as a String if there are lines remaining.
   # Returns nothing if there is no more data.
   def peek_line direct = false
-    if direct || @look_ahead > 0
-      @unescape_next_line ? ((line = @lines[-1]).slice 1, line.length) : @lines[-1]
-    elsif @lines.empty?
-      @look_ahead = 0
-      nil
-    else
+    while true
+      return @unescape_next_line ? ((line = @lines[-1]).slice 1, line.length) : @lines[-1] if direct || @look_ahead > 0
+      if @lines.empty?
+        @look_ahead = 0
+        return
+      end
       # FIXME the problem with this approach is that we aren't
       # retaining the modified line (hence the @unescape_next_line tweak)
       # perhaps we need a stack of proxied lines
-      (process_line @lines[-1]) || peek_line
+      return (process_line @lines[-1]) || redo
     end
   end
 

test/reader_test.rb

@@ -2819,6 +2819,24 @@ def process reader, target, attributes
           assert_empty logger
         end
       end
+
+      test 'should not fail to process preprocessor directive that evaluates to false and has a large number of lines' do
+        lines = (%w(data) * 5000) * ?\n
+        input = <<~EOS
+        before
+
+        ifdef::attribute-not-set[]
+        #{lines}
+        endif::attribute-not-set[]
+
+        after
+        EOS
+
+        doc = Asciidoctor.load input
+        assert_equal 2, doc.blocks.size
+        assert_equal 'before', doc.blocks[0].source
+        assert_equal 'after', doc.blocks[1].source
+      end
     end
   end
 end