Fix cell backgrounds for self-closing tcPr tags

docxtpl/template.py

@@ -135,7 +135,12 @@ def colspan(m):
 
         # manage table cell background color
         def cellbg(m):
-            cell_xml = m.group(1) + m.group(3)
+            cell_xml = re.sub(
+                r"<w:tcPr(\s[^>]*)?/>",
+                r"<w:tcPr\1></w:tcPr>",
+                m.group(1) + m.group(3),
+                count=1,
+            )
             cell_xml = re.sub(
                 r"<w:r[ >](?:(?!<w:r[ >]).)*<w:t></w:t>.*?</w:r>",
                 "",

tests/cellbg_shorthand.py

@@ -0,0 +1,21 @@
+from lxml import etree
+
+from docxtpl import DocxTemplate
+
+
+WORD_NAMESPACE = (
+    "http://schemas.openxmlformats.org/wordprocessingml/2006/main"
+)
+SOURCE_XML = f"""
+<w:tc xmlns:w="{WORD_NAMESPACE}">
+  <w:tcPr />
+  <w:p><w:r><w:t>{{% cellbg background %}}content</w:t></w:r></w:p>
+</w:tc>
+"""
+
+patched_xml = DocxTemplate(None).patch_xml(SOURCE_XML)
+cell = etree.fromstring(patched_xml.encode())
+namespaces = {"w": WORD_NAMESPACE}
+
+assert len(cell.xpath("./w:tcPr/w:shd", namespaces=namespaces)) == 1
+assert len(cell.xpath("./w:shd", namespaces=namespaces)) == 0