Markdown reader: fixed internal header links.

Closes #2397.

This patch also adds `shortcut_reference_links` to the list
of mmd extensions.

3 files changed, 17 insertions, 2 deletions

diff --git a/src/Text/Pandoc/Extensions.hs b/src/Text/Pandoc/Extensions.hs
index f6db6dc0f..b543d489f 100644
--- a/src/Text/Pandoc/Extensions.hs
+++ b/src/Text/Pandoc/Extensions.hs
@@ -247,6 +247,7 @@ multimarkdownExtensions = extensionsFromList
   , Ext_definition_lists
   , Ext_all_symbols_escapable
   , Ext_implicit_header_references
+  , Ext_shortcut_reference_links
   , Ext_auto_identifiers
   , Ext_mmd_header_identifiers
   , Ext_implicit_figures
diff --git a/src/Text/Pandoc/Readers/Markdown.hs b/src/Text/Pandoc/Readers/Markdown.hs
index abaa907e0..2cd1c0d83 100644
--- a/src/Text/Pandoc/Readers/Markdown.hs
+++ b/src/Text/Pandoc/Readers/Markdown.hs
@@ -567,9 +567,14 @@ setextHeaderEnd = try $ do
 
 mmdHeaderIdentifier :: PandocMonad m => MarkdownParser m Attr
 mmdHeaderIdentifier = do
-  ident <- stripFirstAndLast . snd <$> reference
+  (_, raw) <- reference
+  let raw' = trim $ stripFirstAndLast raw
+  let ident = concat $ words $ map toLower raw'
+  let attr = (ident, [], [])
+  guardDisabled Ext_implicit_header_references
+    <|> registerImplicitHeader raw' attr
   skipSpaces
-  return (ident,[],[])
+  return attr
 
 setextHeader :: PandocMonad m => MarkdownParser m (F Blocks)
 setextHeader = try $ do
diff --git a/test/command/2397.md b/test/command/2397.md
new file mode 100644
index 000000000..34d201362
--- /dev/null
+++ b/test/command/2397.md
@@ -0,0 +1,9 @@
+```
+% pandoc -f markdown_mmd
+# Chapter 1: A long name of chapter [Chapter 1]
+
+See [Chapter 1].
+^D
+<h1 id="chapter1">Chapter 1: A long name of chapter</h1>
+<p>See <a href="#chapter1">Chapter 1</a>.</p>
+```