XRENDERING-619: Lists with nested paragraphs are incorrectly converted to XWiki syntax

xwiki-rendering-integration-tests/src/test/resources/simple/list/list15.test

@@ -0,0 +1,106 @@
+.#-----------------------------------------------------
+.input|xhtml/1.0
+.# Test plain text content before a nested list starts.
+.#-----------------------------------------------------
+ <ol>
+   <li>
+     Paragraph 5
+     <ol>
+       <li>Paragraph 5.1
+         <ol>
+           <li>Paragraph 5.1.1
+           <p>Some text.</p>
+           </li>
+         </ol>
+       </li>
+       <li>Paragraph 5.2
+         <ol>
+           <li>Paragraph 5.2.1
+             <p>Example notes:</p>
+           </li>
+         </ol>
+       </li>
+     </ol>
+   </li>
+ </ol>
+.#-----------------------------------------------------
+.expect|xwiki/2.1
+.#-----------------------------------------------------
+1. (((
+Paragraph 5
+
+1. Paragraph 5.1
+11. Paragraph 5.1.1(((
+Some text.
+)))
+1. Paragraph 5.2
+11. Paragraph 5.2.1(((
+Example notes:
+)))
+)))
+.#-----------------------------------------------------
+.expect|event/1.0
+.#-----------------------------------------------------
+beginDocument
+beginList [NUMBERED]
+beginListItem
+onWord [Paragraph]
+onSpace
+onWord [5]
+beginList [NUMBERED]
+beginListItem
+onWord [Paragraph]
+onSpace
+onWord [5]
+onSpecialSymbol [.]
+onWord [1]
+beginList [NUMBERED]
+beginListItem
+onWord [Paragraph]
+onSpace
+onWord [5]
+onSpecialSymbol [.]
+onWord [1]
+onSpecialSymbol [.]
+onWord [1]
+beginGroup
+beginParagraph
+onWord [Some]
+onSpace
+onWord [text]
+onSpecialSymbol [.]
+endParagraph
+endGroup
+endListItem
+endList [NUMBERED]
+endListItem
+beginListItem
+onWord [Paragraph]
+onSpace
+onWord [5]
+onSpecialSymbol [.]
+onWord [2]
+beginList [NUMBERED]
+beginListItem
+onWord [Paragraph]
+onSpace
+onWord [5]
+onSpecialSymbol [.]
+onWord [2]
+onSpecialSymbol [.]
+onWord [1]
+beginGroup
+beginParagraph
+onWord [Example]
+onSpace
+onWord [notes]
+onSpecialSymbol [:]
+endParagraph
+endGroup
+endListItem
+endList [NUMBERED]
+endListItem
+endList [NUMBERED]
+endListItem
+endList [NUMBERED]
+endDocument

xwiki-rendering-syntaxes/xwiki-rendering-syntax-xwiki20/src/main/java/org/xwiki/rendering/internal/renderer/xwiki20/XWikiSyntaxChainingRenderer.java

@@ -907,6 +907,17 @@ private void print(String text)
 
     private void print(String text, boolean isDelayed)
     {
+        // In principle, anything that's printed means that the first element has been rendered, e.g., at the start
+        // of a group syntax.
+        // However, newline handling is not consistent between rendering and parsing.
+        // At the start of a group syntax, the parser detects more empty lines than what the renderer produces if it
+        // prints both the empty lines and the line breaks produced by printEmptyLine() when isFirstElementRendered
+        // is true.
+        // To avoid that, don't set isFirstElementRendered to true when just line breaks are printed.
+        if (!StringUtils.containsOnly(text, '\n')) {
+            this.isFirstElementRendered = true;
+        }
+
         // Handle empty formatting parameters.
         handleEmptyParameters();