From df5ae1c186ed625e25cf6f080ddf24549f7af22e Mon Sep 17 00:00:00 2001
From: John MacFarlane <jgm@berkeley.edu>
Date: Fri, 19 Nov 2021 08:50:18 -0800
Subject: HTML writer: Don't create invalid `data-` attribute...

for empty attribute key. (It would be better to make these
unrepresentable in the type system, but for now this is
an improvement.)

Closes #7546.
---
 src/Text/Pandoc/Writers/HTML.hs | 1 +
 test/command/7546.md            | 6 ++++++
 2 files changed, 7 insertions(+)
 create mode 100644 test/command/7546.md

diff --git a/src/Text/Pandoc/Writers/HTML.hs b/src/Text/Pandoc/Writers/HTML.hs
index 0a4c47387..247cddfc9 100644
--- a/src/Text/Pandoc/Writers/HTML.hs
+++ b/src/Text/Pandoc/Writers/HTML.hs
@@ -633,6 +633,7 @@ toAttrs kvs = do
          return (keys, attrs)
        else return (Set.insert k keys, addAttr html5 mbEpubVersion k v attrs)
   addAttr html5 mbEpubVersion x y
+    | T.null x = id  -- see #7546
     | html5
       = if x `Set.member` (html5Attributes <> rdfaAttributes)
              || T.any (== ':') x -- e.g. epub: namespace
diff --git a/test/command/7546.md b/test/command/7546.md
new file mode 100644
index 000000000..aed17275e
--- /dev/null
+++ b/test/command/7546.md
@@ -0,0 +1,6 @@
+```
+% pandoc -t html -f native
+Span ("", [], [("","")]) []
+^D
+<span></span>
+```
-- 
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