From a0a1424e90b82e98f6408e2a86152fcc0d71abf8 Mon Sep 17 00:00:00 2001
From: DEV-bot <dev-no-reply@weircon.dk>
Date: Mon, 2 Mar 2026 00:31:42 +0000
Subject: [PATCH 1/2] fix(issue-225): honor Accept-Language fallback chain in
 locale resolver

---
 lobby/i18n.py  | 12 ++++++++----
 lobby/tests.py | 22 ++++++++++++++++++++++
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/lobby/i18n.py b/lobby/i18n.py
index 0a8ac89..7d8ad0f 100644
--- a/lobby/i18n.py
+++ b/lobby/i18n.py
@@ -37,10 +37,14 @@ def lobby_i18n_error_messages() -> dict:
 def resolve_locale(request: HttpRequest) -> str:
     default_locale, supported_locales = i18n_locale_config()
 
-    raw_accept_language = (request.META.get("HTTP_ACCEPT_LANGUAGE") or "").split(",", 1)[0]
-    raw_requested = raw_accept_language.split(";", 1)[0].strip().replace("_", "-").split("-", 1)[0].lower()
-    if raw_requested in supported_locales:
-        return raw_requested
+    accept_language = request.META.get("HTTP_ACCEPT_LANGUAGE") or ""
+    for candidate in accept_language.split(","):
+        tag, _sep, quality = candidate.partition(";")
+        if "q=0" in quality.replace(" ", ""):
+            continue
+        normalized = tag.strip().replace("_", "-").split("-", 1)[0].lower()
+        if normalized in supported_locales:
+            return normalized
 
     requested = (get_language_from_request(request) or "").replace("_", "-").split("-", 1)[0].lower()
     if requested in supported_locales:
diff --git a/lobby/tests.py b/lobby/tests.py
index b8ec79d..d89b4ec 100644
--- a/lobby/tests.py
+++ b/lobby/tests.py
@@ -1274,6 +1274,28 @@ class I18nResolverTests(TestCase):
         self.assertEqual(response.status_code, 400)
         self.assertEqual(resolve_locale(response.wsgi_request), "da")
 
+    def test_resolve_locale_uses_next_supported_language_when_primary_is_unsupported(self):
+        response = self.client.post(
+            reverse("lobby:join_session"),
+            data={"code": "", "nickname": "Luna"},
+            content_type="application/json",
+            HTTP_ACCEPT_LANGUAGE="fr-FR, da;q=0.9, en;q=0.8",
+        )
+
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(resolve_locale(response.wsgi_request), "da")
+
+    def test_resolve_locale_skips_q0_languages_and_falls_back_to_next_supported(self):
+        response = self.client.post(
+            reverse("lobby:join_session"),
+            data={"code": "", "nickname": "Luna"},
+            content_type="application/json",
+            HTTP_ACCEPT_LANGUAGE="da;q=0, en;q=0.8",
+        )
+
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(resolve_locale(response.wsgi_request), "en")
+
     def test_resolve_locale_defaults_to_en_when_header_missing(self):
         response = self.client.post(
             reverse("lobby:join_session"),

From c34a52e83e8e695713732fd86db8c0d6841ae502 Mon Sep 17 00:00:00 2001
From: Asger Geel Weirsoee <asger@weircon.dk>
Date: Mon, 2 Mar 2026 00:38:34 +0000
Subject: [PATCH 2/2] Fix Accept-Language q parsing in locale resolver

---
 lobby/i18n.py  | 17 +++++++++++++++--
 lobby/tests.py | 11 +++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/lobby/i18n.py b/lobby/i18n.py
index 7d8ad0f..82fdc0d 100644
--- a/lobby/i18n.py
+++ b/lobby/i18n.py
@@ -34,14 +34,27 @@ def lobby_i18n_error_messages() -> dict:
     return lobby_i18n_catalog().get("backend", {}).get("errors", {})
 
 
+def _quality_value(language_candidate: str) -> float | None:
+    for parameter in language_candidate.split(";")[1:]:
+        key, separator, value = parameter.partition("=")
+        if separator and key.strip().lower() == "q":
+            try:
+                return float(value.strip())
+            except ValueError:
+                return None
+    return None
+
+
 def resolve_locale(request: HttpRequest) -> str:
     default_locale, supported_locales = i18n_locale_config()
 
     accept_language = request.META.get("HTTP_ACCEPT_LANGUAGE") or ""
     for candidate in accept_language.split(","):
-        tag, _sep, quality = candidate.partition(";")
-        if "q=0" in quality.replace(" ", ""):
+        quality = _quality_value(candidate)
+        if quality is not None and quality <= 0:
             continue
+
+        tag = candidate.split(";", 1)[0]
         normalized = tag.strip().replace("_", "-").split("-", 1)[0].lower()
         if normalized in supported_locales:
             return normalized
diff --git a/lobby/tests.py b/lobby/tests.py
index d89b4ec..42e32d1 100644
--- a/lobby/tests.py
+++ b/lobby/tests.py
@@ -1296,6 +1296,17 @@ class I18nResolverTests(TestCase):
         self.assertEqual(response.status_code, 400)
         self.assertEqual(resolve_locale(response.wsgi_request), "en")
 
+    def test_resolve_locale_keeps_q08_languages_eligible_in_accept_language_loop(self):
+        response = self.client.post(
+            reverse("lobby:join_session"),
+            data={"code": "", "nickname": "Luna"},
+            content_type="application/json",
+            HTTP_ACCEPT_LANGUAGE="da;q=0.8, en;q=0.9",
+        )
+
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(resolve_locale(response.wsgi_request), "da")
+
     def test_resolve_locale_defaults_to_en_when_header_missing(self):
         response = self.client.post(
             reverse("lobby:join_session"),