From 70c7c5703afcbd1cbf2a80c2be515e038abcd419 Mon Sep 17 00:00:00 2001
From: Jan Tojnar <jtojnar@gmail.com>
Date: Mon, 7 Dec 2020 07:28:39 +0100
Subject: Docbook writer: Handle admonition titles from Markdown reader
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Docbook reader produces a `Div` with `title` class for `<title>` element
within an “admonition” element. Markdown writer then turns this
into a fenced div with `title` class attribute. Since fenced divs
are block elements, their content is recognized as a paragraph
by the Markdown reader. This is an issue for Docbook writer because
it would produce an invalid DocBook document from such AST –
the `<title>` element can only contain “inline” elements.

Let’s handle this invalid special case separately by unwrapping
the paragraph before creating the `<title>` element.
---
 src/Text/Pandoc/Writers/Docbook.hs |  2 ++
 test/Tests/Writers/Docbook.hs      | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/Text/Pandoc/Writers/Docbook.hs b/src/Text/Pandoc/Writers/Docbook.hs
index 398920839..affa0de04 100644
--- a/src/Text/Pandoc/Writers/Docbook.hs
+++ b/src/Text/Pandoc/Writers/Docbook.hs
@@ -201,6 +201,8 @@ blockToDocbook opts (Div (ident,classes,_) bs) = do
     (l:_) | l `elem` admonitions -> do
         let (mTitleBs, bodyBs) =
                 case bs of
+                  -- Matches AST produced by the DocBook reader → Markdown writer → Markdown reader chain.
+                  (Div (_,["title"],_) [Para ts] : rest) -> (Just (inlinesToDocbook opts ts), rest)
                   -- Matches AST produced by the Docbook reader.
                   (Div (_,["title"],_) ts : rest) -> (Just (blocksToDocbook opts ts), rest)
                   _ -> (Nothing, bs)
diff --git a/test/Tests/Writers/Docbook.hs b/test/Tests/Writers/Docbook.hs
index 1d53dcfe7..621c1280b 100644
--- a/test/Tests/Writers/Docbook.hs
+++ b/test/Tests/Writers/Docbook.hs
@@ -93,6 +93,20 @@ tests = [ testGroup "line blocks"
                                     , "  </para>"
                                     , "</attention>"
                                     ]
+          , "admonition-with-title-in-para" =:
+                            divWith ("foo", ["attention"], []) (
+                              divWith ("foo", ["title"], [])
+                                (para "This is title") <>
+                              para "This is a test"
+                            )
+                              =?> unlines
+                                    [ "<attention id=\"foo\">"
+                                    , "  <title>This is title</title>"
+                                    , "  <para>"
+                                    , "    This is a test"
+                                    , "  </para>"
+                                    , "</attention>"
+                                    ]
           , "single-child" =:
                             divWith ("foo", [], []) (para "This is a test")
                               =?> unlines
-- 
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