Add support for detecting invalid XML that has unsupported content before root element

lib/rexml/parsers/baseparser.rb

@@ -486,11 +486,15 @@ def pull_event
             if text.chomp!("<")
               @source.position -= "<".bytesize
             end
-            if @tags.empty? and @have_root
+            if @tags.empty?
               unless /\A\s*\z/.match?(text)
-                raise ParseException.new("Malformed XML: Extra content at the end of the document (got '#{text}')", @source)
+                if @have_root
+                  raise ParseException.new("Malformed XML: Extra content at the end of the document (got '#{text}')", @source)
+                else
+                  raise ParseException.new("Malformed XML: Content at the start of the document (got '#{text}')", @source)
+                end
               end
-              return pull_event
+              return pull_event if @have_root
             end
             return [ :text, text ]
           end

test/parse/test_comment.rb

@@ -110,6 +110,18 @@ def test_after_doctype_malformed_comment_end
       end
     end
 
+    def test_before_root
+      parser = REXML::Parsers::BaseParser.new('<!-- ok comment --><a></a>')
+
+      events = {}
+      while parser.has_next?
+        event = parser.pull
+        events[event[0]] = event[1]
+      end
+
+      assert_equal(" ok comment ", events[:comment])
+    end
+
     def test_after_root
       parser = REXML::Parsers::BaseParser.new('<a></a><!-- ok comment -->')
 

test/parse/test_processing_instruction.rb

@@ -25,25 +25,6 @@ def test_no_name
         DETAIL
       end
 
-      def test_garbage_text
-        # TODO: This should be parse error.
-        # Create test/parse/test_document.rb or something and move this to it.
-        doc = parse(<<-XML)
-x<?x y
-<!--?><?x -->?>
-<r/>
-        XML
-        pi = doc.children[1]
-        assert_equal([
-                       "x",
-                       "y\n<!--",
-                     ],
-                     [
-                       pi.target,
-                       pi.content,
-                     ])
-      end
-
       def test_xml_declaration_not_at_document_start
         exception = assert_raise(REXML::ParseException) do
           parser = REXML::Parsers::BaseParser.new('<a><?xml version="1.0" ?></a>')
@@ -62,6 +43,30 @@ def test_xml_declaration_not_at_document_start
       end
     end
 
+    def test_comment
+      doc = parse(<<-XML)
+<?x y
+<!--?><?x -->?>
+<r/>
+      XML
+      assert_equal([["x", "y\n<!--"],
+                    ["x", "-->"]],
+                   [[doc.children[0].target, doc.children[0].content],
+                    [doc.children[1].target, doc.children[1].content]])
+    end
+
+    def test_before_root
+      parser = REXML::Parsers::BaseParser.new('<?abc version="1.0" ?><a></a>')
+
+      events = {}
+      while parser.has_next?
+        event = parser.pull
+        events[event[0]] = event[1]
+      end
+
+      assert_equal("abc", events[:processing_instruction])
+    end
+
     def test_after_root
       parser = REXML::Parsers::BaseParser.new('<a></a><?abc version="1.0" ?>')
 

test/parse/test_text.rb

@@ -4,6 +4,23 @@
 module REXMLTests
   class TestParseText < Test::Unit::TestCase
     class TestInvalid < self
+      def test_before_root
+        exception = assert_raise(REXML::ParseException) do
+          parser = REXML::Parsers::BaseParser.new('b<a></a>')
+          while parser.has_next?
+            parser.pull
+          end
+        end
+
+        assert_equal(<<~DETAIL.chomp, exception.to_s)
+          Malformed XML: Content at the start of the document (got 'b')
+          Line: 1
+          Position: 4
+          Last 80 unconsumed characters:
+          <a>
+        DETAIL
+      end
+
       def test_after_root
         exception = assert_raise(REXML::ParseException) do
           parser = REXML::Parsers::BaseParser.new('<a></a>c')