Allow customizing token JSON encoding (#568)

* Allow specifying custom JSONEncoder for TokenBackend

* Make TokenBackend JSONEncoder configurable

rest_framework_simplejwt/backends.py

@@ -1,5 +1,6 @@
+import json
 from datetime import timedelta
-from typing import Union
+from typing import Optional, Type, Union
 
 import jwt
 from django.utils.translation import gettext_lazy as _
@@ -38,6 +39,7 @@ def __init__(
         issuer=None,
         jwk_url: str = None,
         leeway: Union[float, int, timedelta] = None,
+        json_encoder: Optional[Type[json.JSONEncoder]] = None,
     ):
         self._validate_algorithm(algorithm)
 
@@ -53,6 +55,7 @@ def __init__(
             self.jwks_client = None
 
         self.leeway = leeway
+        self.json_encoder = json_encoder
 
     def _validate_algorithm(self, algorithm):
         """
@@ -107,7 +110,12 @@ def encode(self, payload):
         if self.issuer is not None:
             jwt_payload["iss"] = self.issuer
 
-        token = jwt.encode(jwt_payload, self.signing_key, algorithm=self.algorithm)
+        token = jwt.encode(
+            jwt_payload,
+            self.signing_key,
+            algorithm=self.algorithm,
+            json_encoder=self.json_encoder,
+        )
         if isinstance(token, bytes):
             # For PyJWT <= 1.7.1
             return token.decode("utf-8")

rest_framework_simplejwt/settings.py

@@ -20,6 +20,7 @@
     "VERIFYING_KEY": "",
     "AUDIENCE": None,
     "ISSUER": None,
+    "JSON_ENCODER": None,
     "JWK_URL": None,
     "LEEWAY": 0,
     "AUTH_HEADER_TYPES": ("Bearer",),
@@ -44,6 +45,7 @@
 
 IMPORT_STRINGS = (
     "AUTH_TOKEN_CLASSES",
+    "JSON_ENCODER",
     "TOKEN_USER_CLASS",
     "USER_AUTHENTICATION_RULE",
 )

rest_framework_simplejwt/state.py

@@ -9,4 +9,5 @@
     api_settings.ISSUER,
     api_settings.JWK_URL,
     api_settings.LEEWAY,
+    api_settings.JSON_ENCODER,
 )

tests/test_backends.py

@@ -1,4 +1,6 @@
+import uuid
 from datetime import datetime, timedelta
+from json import JSONEncoder
 from unittest import mock
 from unittest.mock import patch
 
@@ -34,6 +36,13 @@
 IS_OLD_JWT = jwt_version == "1.7.1"
 
 
+class UUIDJSONEncoder(JSONEncoder):
+    def default(self, obj):
+        if isinstance(obj, uuid.UUID):
+            return str(obj)
+        return super().default(obj)
+
+
 class TestTokenBackend(TestCase):
     def setUp(self):
         self.hmac_token_backend = TokenBackend("HS256", SECRET)
@@ -329,3 +338,11 @@ def test_decode_leeway_hmac_success(self):
             self.hmac_leeway_token_backend.decode(expired_token),
             self.payload,
         )
+
+    def test_custom_JSONEncoder(self):
+        backend = TokenBackend("HS256", SECRET, json_encoder=UUIDJSONEncoder)
+        unique = uuid.uuid4()
+        self.payload["uuid"] = unique
+        token = backend.encode(self.payload)
+        decoded = backend.decode(token)
+        self.assertEqual(decoded["uuid"], str(unique))