[321775] Allow parsing Dot Html-Like-Label comments in Html tags.

- Modify the DotHtmlLabel grammar to send the HTML_COMMENT elements
nested in a HtmlTag to the hidden channel.
- Implement corresponding DotHtmlLabelTests parser/validation test
cases.

org.eclipse.gef.dot.tests/src/org/eclipse/gef/dot/tests/DotHtmlLabelTests.java

@@ -78,6 +78,16 @@ public void test_comment_with_close_tag() throws Throwable {
 		parse(DotTestHtmlLabels.COMMENT_WITH_CLOSE_TAG);
 	}
 
+	@Test
+	public void test_comment_within_table_tag() throws Throwable {
+		parse(DotTestHtmlLabels.COMMENT_WITHIN_TABLE_TAG);
+	}
+
+	@Test
+	public void test_comment_within_text() throws Throwable {
+		parse(DotTestHtmlLabels.COMMENT_WITHIN_TEXT);
+	}
+
 	@Test(timeout = 2000)
 	public void test_tag_with_attribute() {
 		parse(DotTestHtmlLabels.TAG_WITH_ATTRIBUTE);
@@ -140,6 +150,17 @@ public void test_self_closing_tags() {
 	 ************************************************************************************************************
 	 */
 
+	@Test
+	public void test_invalid_comment() throws Throwable {
+		// HTML comments are not allowed inside a tag
+		String text = "<B <!--HTML comment--> >string</B>";
+
+		HtmlLabel htmlLabel = parseHelper.parse(text);
+
+		// verify that there are some reported issues
+		Assert.assertEquals(8, validationTestHelper.validate(htmlLabel).size());
+	}
+
 	@Test
 	public void test_tag_wrongly_closed() throws Exception {
 		String text = "<test>string</B>";

org.eclipse.gef.dot.tests/src/org/eclipse/gef/dot/tests/DotTestHtmlLabels.xtend

@@ -43,6 +43,27 @@ class DotTestHtmlLabels {
 		<!-- <tags> -->
 		<B>Bold Label</B>
 	'''
+
+	public static val COMMENT_WITHIN_TABLE_TAG = '''
+			<TABLE>
+				<!-- HTML comment-->
+				<TR>
+					<TD>left</TD>
+				</TR>
+			</TABLE>
+	'''
+
+	public static val COMMENT_WITHIN_TEXT= '''
+			<TABLE>
+				<TR>
+					<TD>
+						left  <!-- HTML comment 1 -->
+						      <!-- HTML comment 2 -->
+						right <!-- HTML comment 3 -->
+					</TD>
+				</TR>
+			</TABLE>
+	'''
 
 	public static val FONT_TAG_CONTAINS_TABLE_TAG = '''
 		<!--

org.eclipse.gef.dot/src/org/eclipse/gef/dot/internal/language/DotHtmlLabel.xtext

@@ -28,7 +28,7 @@ HtmlContent: tag=HtmlTag | text=TEXT;
  * FIXME: 'HtmlTag' should not support the 'closeName' feature. The closeName is only needed for
  * validation to check if the tag is opened and closed with the same name.
  */
-HtmlTag hidden(WS): TAG_START name=ID (attributes+=HtmlAttr)*
+HtmlTag hidden(WS, HTML_COMMENT): TAG_START name=ID (attributes+=HtmlAttr)*
 	( selfClosing?=TAG_END_CLOSE
 	| TAG_END (children+=HtmlContent)* TAG_START_CLOSE closeName=ID TAG_END
 	);