Fix endless loop with invalid PI containing XML (codehaus-plexus#122)

This closes codehaus-plexus#122

Author: joehni

src/main/java/org/codehaus/plexus/util/xml/pull/MXParser.java

@@ -3158,6 +3158,10 @@ else if ( !seenInnerTag )
                         throw new XmlPullParserException( "processing instruction started on line " + curLine
                             + " and column " + curColumn + " was not closed", this, null );
                     }
+                    else
+                    {
+                        seenInnerTag = false;
+                    }
                 }
                 else if ( ch == '<' )
                 {

src/test/java/org/codehaus/plexus/util/xml/pull/MXParserTest.java

@@ -432,6 +432,37 @@ public void testProcessingInstructionsContainingXml()
      *
      * @throws java.lang.Exception if any.
      */
+    @Test
+    public void testMalformedProcessingInstructionsContainingXmlNoClosingQuestionMark()
+        throws Exception
+    {
+        StringBuffer sb = new StringBuffer();
+        sb.append( "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" );
+        sb.append( "<project />\n" );
+        sb.append( "<?pi\n" );
+        sb.append( "   <tag>\n" );
+        sb.append( "   </tag>>\n" );
+
+        MXParser parser = new MXParser();
+        parser.setInput( new StringReader( sb.toString() ) );
+
+        try
+        {
+            assertEquals( XmlPullParser.PROCESSING_INSTRUCTION, parser.nextToken() );
+            assertEquals( XmlPullParser.IGNORABLE_WHITESPACE, parser.nextToken() );
+            assertEquals( XmlPullParser.START_TAG, parser.nextToken() );
+            assertEquals( XmlPullParser.END_TAG, parser.nextToken() );
+            assertEquals( XmlPullParser.IGNORABLE_WHITESPACE, parser.nextToken() );
+            assertEquals( XmlPullParser.PROCESSING_INSTRUCTION, parser.nextToken() );
+
+            fail( "Should fail since it has invalid PI" );
+        }
+        catch ( XmlPullParserException ex )
+        {
+            assertTrue( ex.getMessage().contains( "processing instruction started on line 3 and column 1 was not closed" ) );
+        }
+    }
+
     @Test
     public void testSubsequentProcessingInstructionShort()
         throws Exception