XRENDERING-765: HTML parsing error on saving attempt page that has empty line at the start of the link

* Make HTML parsing more robust by ignoring stray stopmacro and stopwikilink comments instead of failing to parse.

(cherry picked from commit 0a8726f)

Author: michitux

xwiki-rendering-syntaxes/xwiki-rendering-syntax-xhtml/src/main/java/org/xwiki/rendering/internal/parser/xhtml/wikimodel/XWikiCommentHandler.java

@@ -234,6 +234,12 @@ private void handleLinkCommentStart(String content, TagStack stack)
 
     private void handleLinkCommentStop(TagStack stack)
     {
+        // If there's no active link listener, it means we received a stopwikilink outside a link context
+        // (e.g., duplicated by the browser while fixing malformed HTML). In that case, ignore it.
+        if (stack.getStackParameter(LINK_LISTENER) == null) {
+            return;
+        }
+
         XWikiGeneratorListener xwikiListener =
             (XWikiGeneratorListener) stack.popStackParameter(LINK_LISTENER);
         XDOMGeneratorListener linkLabelRenderer = (XDOMGeneratorListener) xwikiListener.getListener();
@@ -269,6 +275,11 @@ private void handleImageCommentStart(String content, TagStack stack)
 
     private void handleImageCommentStop(TagStack stack)
     {
+        // Ignore stray stopimage if there's no image context.
+        if (!Boolean.TRUE.equals(stack.getStackParameter(IS_IN_IMAGE))) {
+            return;
+        }
+
         boolean isFreeStandingImage = (Boolean) stack.getStackParameter(IS_FREE_STANDING_IMAGE);
 
         ResourceReference imageReference =

xwiki-rendering-syntaxes/xwiki-rendering-syntax-xhtml/src/test/resources/xhtml10/specific/link/link10.test

@@ -0,0 +1,49 @@
+.#-----------------------------------------------------
+.input|xhtml/1.0
+.# Stray stopmacro and stopwikilink comments
+.#-----------------------------------------------------
+<p><!--startwikilink:false|-|url|-|https://www.xwiki.org/xwiki/bin/view/Main/--><span class="wikiexternallink"><a
+href="https://www.xwiki.org/xwiki/bin/view/Main/"><!--startmacro:info|-||-|Type your information message here.--><!--stopmacro--></a></span><!--stopwikilink--></p><div
+ class="box infomessage"><a href="https://www.xwiki.org/xwiki/bin/view/Main/"><span class="sr-only">Information</span></a><p><a
+ href="https://www.xwiki.org/xwiki/bin/view/Main/"><span data-xwiki-non-generated-content="java.util.List&lt;org.xwiki.rendering.block.Block&gt;"
+ class="xwiki-metadata-container">Type your information message here.</span></a></p></div><!--stopmacro--><!--stopwikilink--><p>&nbsp;</p>
+.#-----------------------------------------------------
+.expect|event/1.0
+.#-----------------------------------------------------
+beginDocument
+beginParagraph
+beginLink [Typed = [false] Type = [url] Reference = [https://www.xwiki.org/xwiki/bin/view/Main/]] [false]
+onMacroInline [info] [] [Type your information message here.]
+endLink [Typed = [false] Type = [url] Reference = [https://www.xwiki.org/xwiki/bin/view/Main/]] [false]
+endParagraph
+beginGroup [[class]=[box infomessage]]
+beginParagraph
+beginLink [Typed = [true] Type = [url] Reference = [https://www.xwiki.org/xwiki/bin/view/Main/]] [false]
+beginFormat [NONE] [[class]=[sr-only]]
+onWord [Information]
+endFormat [NONE] [[class]=[sr-only]]
+endLink [Typed = [true] Type = [url] Reference = [https://www.xwiki.org/xwiki/bin/view/Main/]] [false]
+beginLink [Typed = [true] Type = [url] Reference = [https://www.xwiki.org/xwiki/bin/view/Main/]] [false]
+beginMetaData [[non-generated-content]=[java.util.List<org.xwiki.rendering.block.Block>]]
+onWord [Type]
+onSpace
+onWord [your]
+onSpace
+onWord [information]
+onSpace
+onWord [message]
+onSpace
+onWord [here]
+onSpecialSymbol [.]
+endMetaData [[non-generated-content]=[java.util.List<org.xwiki.rendering.block.Block>]]
+endLink [Typed = [true] Type = [url] Reference = [https://www.xwiki.org/xwiki/bin/view/Main/]] [false]
+endParagraph
+endGroup [[class]=[box infomessage]]
+beginParagraph
+onSpace
+endParagraph
+endDocument
+.#-----------------------------------------------------
+.expect|xhtml/1.0
+.#-----------------------------------------------------
+<p><span class="wikiexternallink"><a href="https://www.xwiki.org/xwiki/bin/view/Main/"></a></span></p><div class="box infomessage"><p><span class="wikiexternallink"><a href="https://www.xwiki.org/xwiki/bin/view/Main/"><span class="sr-only">Information</span></a></span><span class="wikiexternallink"><a href="https://www.xwiki.org/xwiki/bin/view/Main/">Type your information message here.</a></span></p></div><p>&nbsp;</p>