check hidden (unwanted) ascii control sequence character. Closes: #1596

lib/review/book/chapter.rb

@@ -85,6 +85,8 @@ def find_first_header_option
           nil
         rescue ArgumentError => e
           raise ReVIEW::CompileError, "#{@name}: #{e}"
+        rescue SyntaxError => e
+          raise ReVIEW::SyntaxError, "#{@name}:#{f.lineno}: #{e}"
         end
       end
 

lib/review/compiler.rb

@@ -333,6 +333,8 @@ def do_compile
         end
       end
       close_all_tagged_section
+    rescue SyntaxError => e
+      error e
     end
 
     def compile_minicolumn_begin(name, caption = nil)

lib/review/lineinput.rb

@@ -13,5 +13,21 @@ def skip_comment_lines
       end
       n
     end
+
+    def gets
+      unless @buf.empty?
+        @lineno += 1
+        return @buf.pop
+      end
+      return nil if @eof_p # to avoid ARGF blocking.
+      line = @input.gets
+      @eof_p = true unless line
+      @lineno += 1
+      if line =~ /[\x00-\x08]/ || line =~ /[\x0b-\x0c]/ || line =~ /[\x0e-\x1f]/
+        # accept 0x09: TAB, 0x0a: LF, 0x0d: CR
+        raise SyntaxError, "found invalid control-sequence character (#{sprintf('%#x', $&.codepoints[0])})."
+      end
+      line
+    end
   end
 end

test/test_lineinput.rb

@@ -1,5 +1,6 @@
 require 'test_helper'
-require 'lineinput'
+require 'review/lineinput'
+require 'review/exception'
 require 'tempfile'
 require 'stringio'
 
@@ -178,4 +179,18 @@ def test_until_terminator2
     assert_equal ["abc\n", "def\n"], data
     assert_equal 3, li.lineno
   end
+
+  def test_invalid_control_sequence
+    0.upto(31) do |n|
+      content = n.chr
+      io = StringIO.new(content)
+      li = ReVIEW::LineInput.new(io)
+      if [9, 10, 13].include?(n) # TAB, LF, CR
+        assert_equal content, li.gets
+      else
+        e = assert_raise(ReVIEW::SyntaxError) { li.gets }
+        assert_match(/found invalid control/, e.message)
+      end
+    end
+  end
 end