Fix ordering inside searchindex.js not being deterministic

Fixes sphinx-doc#11622

CHANGES

@@ -1,3 +1,23 @@
+Release 7.2.6 (in development)
+==============================
+
+Dependencies
+------------
+
+Incompatible changes
+--------------------
+
+Deprecated
+----------
+
+Features added
+--------------
+
+Bugs fixed
+----------
+
+* #11622: Fix ordering inside searchindex.js not being deterministic.
+
 Release 7.2.5 (released Aug 30, 2023)
 =====================================
 

sphinx/search/__init__.py

@@ -162,7 +162,7 @@ class _JavaScriptIndex:
     SUFFIX = ')'
 
     def dumps(self, data: Any) -> str:
-        return self.PREFIX + json.dumps(data) + self.SUFFIX
+        return self.PREFIX + json.dumps(data, sort_keys=True) + self.SUFFIX
 
     def loads(self, s: str) -> Any:
         data = s[len(self.PREFIX):-len(self.SUFFIX)]

tests/test_search.py

@@ -304,3 +304,26 @@ def test_parallel(app):
     app.build()
     index = load_searchindex(app.outdir / 'searchindex.js')
     assert index['docnames'] == ['index', 'nosearch', 'tocitem']
+
+
+@pytest.mark.sphinx(testroot='search')
+def test_search_index_is_deterministic(app):
+    app.builder.build_all()
+    index = load_searchindex(app.outdir / 'searchindex.js')
+
+    def check_if_dicts_are_sorted(item):
+        if type(item) == dict:
+            keys = list(item.keys())
+            if not all(keys[i] <= keys[i + 1] for i in range(len(keys) - 1)):
+                raise RuntimeError(f'keys are not sorted: {item!r}')
+
+            for child in item.values():
+                check_if_dicts_are_sorted(child)
+        # Lists in the search index cannot be sorted: for some lists, their
+        # position inside the list is referenced elsewhere in the index, so if
+        # we were to sort lists, the search index would break.
+        elif type(item) == list:
+            for child in item:
+                check_if_dicts_are_sorted(child)
+
+    check_if_dicts_are_sorted(index)