From c79c50d729b6eb27367ff58136f1b589682b4065 Mon Sep 17 00:00:00 2001
From: Pietro Albini <pietro.albini@ferrous-systems.com>
Date: Fri, 1 Sep 2023 10:15:55 +0200
Subject: [PATCH] Fix ordering inside searchindex.js not being deterministic

Fixes #11622
---
 CHANGES.rst               |  1 +
 sphinx/search/__init__.py |  2 +-
 tests/test_search.py      | 20 ++++++++++++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index 10abb27b452..2c3961ec42b 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -18,6 +18,7 @@ Bugs fixed
 
 * #11668: Raise a useful error when ``theme.conf`` is missing.
   Patch by Vinay Sajip.
+* #11622: Fix ordering inside searchindex.js not being deterministic.
 
 Testing
 -------
diff --git a/sphinx/search/__init__.py b/sphinx/search/__init__.py
index 21758d3f424..114d7fe9072 100644
--- a/sphinx/search/__init__.py
+++ b/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)]
diff --git a/tests/test_search.py b/tests/test_search.py
index 68a7b01aa55..0fdc0642343 100644
--- a/tests/test_search.py
+++ b/tests/test_search.py
@@ -304,3 +304,23 @@ 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 isinstance(item, dict):
+            assert list(item.keys()) == sorted(item.keys())
+            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 isinstance(item, list):
+            for child in item:
+                check_if_dicts_are_sorted(child)
+
+    check_if_dicts_are_sorted(index)