Markdown writer: render a figure with Para caption as implicit figure.

Also, when falling back to a Div with class `figure` for a figure
that can't be represented any other way, include a Div with class
`caption` containing the caption.

Closes #10755.

src/Text/Pandoc/Writers/Markdown.hs

@@ -717,6 +717,8 @@ blockToMarkdown' opts (Figure figattr capt body) = do
                               else Just alt
         Caption Nothing [Plain captInlines]
           | captInlines == alt || null alt -> Just captInlines
+        Caption Nothing [Para captInlines]
+          | captInlines == alt || null alt -> Just captInlines
         _ -> Nothing
   case body of
     [Plain [Image imgAttr alt (src, ttl)]]
@@ -763,8 +765,11 @@ figureToMarkdown opts attr@(ident, classes, kvs) capt body
       writeHtml5String
         opts{ writerTemplate = Nothing }
         (Pandoc nullMeta [Figure attr capt body])
-  | otherwise = let attr' = (ident, ["figure"] `union` classes, kvs)
-                in blockToMarkdown' opts (Div attr' body)
+  | otherwise = do
+      let attr' = (ident, ["figure"] `union` classes, kvs)
+      let Caption _mbshort caption = capt
+      let captionBs = [Div ("",["caption"],[]) caption | not (null caption)]
+      blockToMarkdown' opts (Div attr' (body <> captionBs))
 
 itemEndsWithTightList :: [Block] -> Bool
 itemEndsWithTightList bs =

test/command/10755.md

@@ -0,0 +1,71 @@
+```
+% pandoc -f native -t markdown
+[ Figure
+    ( "" , [] , [] )
+    (Caption
+       Nothing [ Para [ Str "An" , Space , Str "image." ] ])
+    [ Plain
+        [ Image
+            ( ""
+            , []
+            , []
+            )
+            [ Str "An" , Space , Str "image." ]
+            ( "media/rId20.jpg" , "" )
+        ]
+    ]
+]
+^D
+![An image.](media/rId20.jpg)
+```
+
+```
+% pandoc -f native -t markdown -t markdown-implicit_figures
+[ Figure
+    ( "" , [] , [] )
+    (Caption
+       Nothing [ Para [ Str "An" , Space , Str "image." ] ])
+    [ Plain
+        [ Image
+            ( ""
+            , []
+            , []
+            )
+            [ Str "An" , Space , Str "image." ]
+            ( "media/rId20.jpg" , "" )
+        ]
+    ]
+]
+^D
+<figure>
+<img src="media/rId20.jpg" alt="An image." />
+<figcaption aria-hidden="true"><p>An image.</p></figcaption>
+</figure>
+```
+
+```
+% pandoc -f native -t markdown -t markdown-implicit_figures-raw_html
+[ Figure
+    ( "" , [] , [] )
+    (Caption
+       Nothing [ Para [ Str "An" , Space , Str "image." ] ])
+    [ Plain
+        [ Image
+            ( ""
+            , []
+            , []
+            )
+            [ Str "An" , Space , Str "image." ]
+            ( "media/rId20.jpg" , "" )
+        ]
+    ]
+]
+^D
+:::: figure
+![An image.](media/rId20.jpg)
+
+::: caption
+An image.
+:::
+::::
+```