MediaWiki writer: don't softbreak lines inside list items.

Closes #3531.

src/Text/Pandoc/Writers/MediaWiki.hs

@@ -409,10 +409,13 @@ inlineToMediaWiki LineBreak = return "<br />\n"
 
 inlineToMediaWiki SoftBreak = do
   wrapText <- gets (writerWrapText . stOptions)
+  listlevel <- asks listLevel
   case wrapText of
        WrapAuto     -> return " "
        WrapNone     -> return " "
-       WrapPreserve -> return "\n"
+       WrapPreserve -> if null listlevel
+                          then return "\n"
+                          else return " "
 
 inlineToMediaWiki Space = return " "
 

test/command/3531.md

@@ -0,0 +1,19 @@
+```
+% pandoc -t mediawiki --wrap=preserve
+* This is a list item.
+* This is a list item in Markdown. It is
+  continued in the next line.
+    * It has a sub-item.
+* This is the next list item.
+
+A paragraph can span multiple lines
+without being broken into pieces.
+^D
+* This is a list item.
+* This is a list item in Markdown. It is continued in the next line.
+** It has a sub-item.
+* This is the next list item.
+
+A paragraph can span multiple lines
+without being broken into pieces.
+```