Restore correct parallel search index building (#11192)

Revert b32841e
to fix parallel search index building

The image-related changes were already reverted in
2a7c40d,
but the search index changes also need to be reverted.

It would be nice to support parallel search index building, but the
necessary support for merging the search indices produced by each
process needs to be added first.

sphinx/builders/html/__init__.py

@@ -655,10 +655,6 @@ def get_doc_context(self, docname: str, body: str, metatags: str) -> dict[str, A
         }
 
     def write_doc(self, docname: str, doctree: nodes.document) -> None:
-        title_node = self.env.longtitles.get(docname)
-        title = self.render_partial(title_node)['title'] if title_node else ''
-        self.index_page(docname, doctree, title)
-
         destination = StringOutput(encoding='utf-8')
         doctree.settings = self.docsettings
 
@@ -678,6 +674,9 @@ def write_doc(self, docname: str, doctree: nodes.document) -> None:
     def write_doc_serialized(self, docname: str, doctree: nodes.document) -> None:
         self.imgpath = relative_uri(self.get_target_uri(docname), self.imagedir)
         self.post_process_images(doctree)
+        title_node = self.env.longtitles.get(docname)
+        title = self.render_partial(title_node)['title'] if title_node else ''
+        self.index_page(docname, doctree, title)
 
     def finish(self) -> None:
         self.finish_tasks.add_task(self.gen_indices)

tests/test_search.py

@@ -286,3 +286,10 @@ def test_nosearch(app):
     assert 'latex' not in index['terms']
     assert 'zfs' in index['terms']
     assert index['terms']['zfs'] == []  # zfs on nosearch.rst is not registered to index
+
+
+@pytest.mark.sphinx(testroot='search', parallel=3, freshenv=True)
+def test_parallel(app):
+    app.build()
+    index = load_searchindex(app.outdir / 'searchindex.js')
+    assert index['docnames'] == ['index', 'nosearch', 'tocitem']