Ignore empty abbreviation definitions in element tails

docs/changelog.md

@@ -18,6 +18,8 @@ See the [Contributing Guide](contributing.md) for details.
 
 * Fix quadratic-time id generation in the `toc` extension when many headers
   share the same text.
+* Ignore glossary abbreviations with empty definitions after inline elements,
+  consistently with abbreviations before inline elements.
 * Strip complete HTML tags with quoted `>` characters from `toc` labels and
   generated heading IDs.
 * Fix quadratic-time regex backtracking in `attr_list` when a block ends with an

markdown/extensions/abbr.py

@@ -119,9 +119,10 @@ def iter_element(self, el: etree.Element, parent: etree.Element | None = None) -
             index = list(parent).index(el) + 1
             if not isinstance(tail, AtomicString):
                 for m in reversed(list(self.RE.finditer(tail))):
-                    abbr = self.create_element(self.abbrs[m.group(0)], m.group(0), tail[m.end():])
-                    parent.insert(index, abbr)
-                    tail = tail[:m.start()]
+                    if self.abbrs[m.group(0)]:
+                        abbr = self.create_element(self.abbrs[m.group(0)], m.group(0), tail[m.end():])
+                        parent.insert(index, abbr)
+                        tail = tail[:m.start()]
                 el.tail = tail
 
     def run(self, root: etree.Element) -> etree.Element | None:

tests/test_syntax/extensions/test_abbr.py

@@ -178,6 +178,14 @@ def test_abbr_glossary(self):
             extensions=[AbbrExtension(glossary=glossary)]
         )
 
+    def test_abbr_glossary_empty_definition(self):
+        self.assertMarkdownRenders(
+            'HTML W3C HTML *word* HTML W3C HTML',
+            '<p>HTML <abbr title="World Wide Web Consortium">W3C</abbr> HTML '
+            '<em>word</em> HTML <abbr title="World Wide Web Consortium">W3C</abbr> HTML</p>',
+            extensions=[AbbrExtension(glossary={'HTML': '', 'W3C': 'World Wide Web Consortium'})]
+        )
+
     def test_abbr_glossary_2(self):
 
         glossary = {