Shared: improve isTightList...

so that it recognizes an item containing only a list which is
itself tight as potentially an item in a tight list.

Closes #9161.

src/Text/Pandoc/Shared.hs

@@ -633,9 +633,13 @@ onlySimpleTableCells = all isSimpleCell . concat
 
 -- | Detect if a list is tight.
 isTightList :: [[Block]] -> Bool
-isTightList = all (\item -> firstIsPlain item || null item)
-  where firstIsPlain (Plain _ : _) = True
-        firstIsPlain _             = False
+isTightList = all isPlainItem
+  where
+    isPlainItem [] = True
+    isPlainItem (Plain _ : _) = True
+    isPlainItem [BulletList xs] = isTightList xs
+    isPlainItem [OrderedList _ xs] = isTightList xs
+    isPlainItem _ = False
 
 -- | Convert a list item containing tasklist syntax (e.g. @[x]@)
 -- to using @U+2610 BALLOT BOX@ or @U+2612 BALLOT BOX WITH X@.

test/command/8150.md

@@ -12,12 +12,9 @@ Nested bullet lists
 </ul>
 ^D
 -   L1
-
 -   L2
-
 -   -   L3.1
     -   L3.2
-
 -   L4
 ```
 
@@ -34,9 +31,7 @@ Nested ordered lists
 </ol>
 ^D
 1.  L1
-
 2.  L2
-
 3.  1.  L3.1
     2.  L3.2
 ```
@@ -54,9 +49,7 @@ Ordered list nested below an unordered list
 </ul>
 ^D
 -   L1
-
 -   L2
-
 -   1.  L3.1
     2.  L3.2
 ```

test/command/lists-inside-definition.md

@@ -10,6 +10,7 @@ Definition
     2. list
 ^D
 \begin{description}
+\tightlist
 \item[Definition]
 \begin{enumerate}
 \def\labelenumi{\arabic{enumi}.}
@@ -53,6 +54,7 @@ Definition
     - list
 ^D
 \begin{description}
+\tightlist
 \item[Definition]
 \begin{itemize}
 \tightlist