fix lineno on reader when skip-front-matter attribute is set but end of front matter is not found

3 files changed, 35 insertions, 19 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index fa846fbf..707a6fb1 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -59,6 +59,7 @@ Bug Fixes::
   * If path is included both partially and fully, store it with true value (included fully) in includes table of document catalog
   * Reset registry if activate is called on it again (#4256)
   * Format source location in exception message when extension code is malformed
+  * Fix lineno on reader when `skip-front-matter` attribute is set but end of front matter is not found
 
 // tag::compact[]
 == 2.0.17 (2022-01-05) - @mojavelinux
diff --git a/lib/asciidoctor/reader.rb b/lib/asciidoctor/reader.rb
index 257557e3..4f419d75 100644
--- a/lib/asciidoctor/reader.rb
+++ b/lib/asciidoctor/reader.rb
@@ -1267,27 +1267,22 @@ class PreprocessorReader < Reader
 
   # Private: Ignore front-matter, commonly used in static site generators
   def skip_front_matter! data, increment_linenos = true
-    front_matter = nil
-    if data[0] == '---'
-      original_data = data.drop 0
-      data.shift
-      front_matter = []
+    return unless (delim = data[0]) == '---'
+    original_data = data.drop 0
+    data.shift
+    front_matter = []
+    @lineno += 1 if increment_linenos
+    until (eof = data.empty?) || data[0] == delim
+      front_matter << data.shift
       @lineno += 1 if increment_linenos
-      while !data.empty? && data[0] != '---'
-        front_matter << data.shift
-        @lineno += 1 if increment_linenos
-      end
-
-      if data.empty?
-        data.unshift(*original_data)
-        @lineno = 0 if increment_linenos
-        front_matter = nil
-      else
-        data.shift
-        @lineno += 1 if increment_linenos
-      end
     end
-
+    if eof
+      data.unshift(*original_data)
+      @lineno -= original_data.size if increment_linenos
+      return
+    end
+    data.shift
+    @lineno += 1 if increment_linenos
     front_matter
   end
 
diff --git a/test/reader_test.rb b/test/reader_test.rb
index 21269525..edd0aaa6 100644
--- a/test/reader_test.rb
+++ b/test/reader_test.rb
@@ -511,6 +511,25 @@ class ReaderTest < Minitest::Test
         reader = doc.reader
         refute doc.attributes.key?('front-matter')
         assert_equal '---', reader.peek_line
+        assert_equal 1, reader.lineno
+      end
+
+      test 'should not skip front matter if ending delimiter is not found' do
+        input = <<~'EOS'
+        ---
+        title: Document Title
+        tags: [ first, second ]
+        = Document Title
+        Author Name
+
+        preamble
+        EOS
+
+        doc = Asciidoctor::Document.new input, attributes: { 'skip-front-matter' => '' }
+        reader = doc.reader
+        assert_equal '---', reader.peek_line
+        refute doc.attributes.key? 'front-matter'
+        assert_equal 1, reader.lineno
       end
 
       test 'should skip front matter if specified by skip-front-matter attribute' do
@@ -535,6 +554,7 @@ class ReaderTest < Minitest::Test
         reader = doc.reader
         assert_equal '= Document Title', reader.peek_line
         assert_equal front_matter, doc.attributes['front-matter']
+        assert_equal 7, reader.lineno
       end
     end