Fix invalid genindex.html file produced with translated docs (#12495)

CHANGES.rst

@@ -86,6 +86,9 @@ Bugs fixed
 * #12331: Resolve data-URI-image-extraction regression from v7.3.0 affecting
   builders without native support for data-URIs in their output format.
   Patch by James Addison.
+* #12494: Fix invalid genindex.html file produced with translated docs
+  (regression in 7.1.0).
+  Patch by Nicolas Peugnet.
 
 Testing
 -------

sphinx/domains/std/__init__.py

@@ -272,7 +272,7 @@ def split_term_classifiers(line: str) -> tuple[str, str | None]:
     return term, first_classifier
 
 
-def make_glossary_term(env: BuildEnvironment, textnodes: Iterable[Node], index_key: str,
+def make_glossary_term(env: BuildEnvironment, textnodes: Iterable[Node], index_key: str | None,
                        source: str, lineno: int, node_id: str | None, document: nodes.document,
                        ) -> nodes.term:
     # get a text-only representation of the term and register it
@@ -395,7 +395,7 @@ def run(self) -> list[Node]:
 
                 # use first classifier as a index key
                 term = make_glossary_term(self.env, textnodes,
-                                          first_classifier, source, lineno,  # type: ignore[arg-type]
+                                          first_classifier, source, lineno,
                                           node_id=None, document=self.state.document)
                 term.rawsource = line
                 system_messages.extend(sysmsg)

sphinx/transforms/i18n.py

@@ -411,7 +411,7 @@ def apply(self, **kwargs: Any) -> None:
                         self.app, term or '', source, node.line, self.config, settings,  # type: ignore[arg-type]
                     )
                     updater.patch = make_glossary_term(
-                        self.env, patch, first_classifier or '',
+                        self.env, patch, first_classifier,
                         source, node.line, _id, self.document,  # type: ignore[arg-type]
                     )
                     processed = True

tests/test_intl/test_intl.py

@@ -938,6 +938,16 @@ def wrap_nest(parenttag, childtag, keyword):
         start_tag2 = "<%s[^>]*>" % childtag
         return fr"{start_tag1}\s*{keyword}\s*{start_tag2}"
     expected_exprs = [
+        wrap('h2', 'Symbols'),
+        wrap('h2', 'C'),
+        wrap('h2', 'E'),
+        wrap('h2', 'F'),
+        wrap('h2', 'M'),
+        wrap('h2', 'N'),
+        wrap('h2', 'R'),
+        wrap('h2', 'S'),
+        wrap('h2', 'T'),
+        wrap('h2', 'V'),
         wrap('a', 'NEWSLETTER'),
         wrap('a', 'MAILING LIST'),
         wrap('a', 'RECIPIENTS LIST'),