Respect the json_provider_class

Respect the json_provider_class when available and stay compatible
with flask < 2.2. Extended tox configuration to also test with flask < 2.2.

flask_jwt_extended/config.py

@@ -1,6 +1,7 @@
 from datetime import datetime
 from datetime import timedelta
 from datetime import timezone
+from json import JSONEncoder
 from typing import Iterable
 from typing import List
 from typing import Optional
@@ -11,7 +12,7 @@
 from flask import current_app
 from jwt.algorithms import requires_cryptography
 
-from flask_jwt_extended.json_encoder import JSONEncoder
+from flask_jwt_extended.internal_utils import get_json_encoder
 from flask_jwt_extended.typing import ExpiresDelta
 
 
@@ -284,7 +285,7 @@ def error_msg_key(self) -> str:
 
     @property
     def json_encoder(self) -> Type[JSONEncoder]:
-        return JSONEncoder
+        return get_json_encoder(current_app)
 
     @property
     def decode_audience(self) -> Union[str, Iterable[str]]:

flask_jwt_extended/internal_utils.py

@@ -1,12 +1,25 @@
+import json
 from typing import Any
+from typing import Type
 from typing import TYPE_CHECKING
 
 from flask import current_app
+from flask import Flask
 
 from flask_jwt_extended.exceptions import RevokedTokenError
 from flask_jwt_extended.exceptions import UserClaimsVerificationError
 from flask_jwt_extended.exceptions import WrongTokenError
 
+try:
+    from flask.json.provider import DefaultJSONProvider
+
+    HAS_JSON_PROVIDER = True
+except ModuleNotFoundError:  # pragma: no cover
+    # The flask.json.provider module was added in Flask 2.2.
+    # Further details are handled in get_json_encoder.
+    HAS_JSON_PROVIDER = False
+
+
 if TYPE_CHECKING:  # pragma: no cover
     from flask_jwt_extended import JWTManager
 
@@ -51,3 +64,31 @@ def custom_verification_for_token(jwt_header: dict, jwt_data: dict) -> None:
     if not jwt_manager._token_verification_callback(jwt_header, jwt_data):
         error_msg = "User claims verification failed"
         raise UserClaimsVerificationError(error_msg, jwt_header, jwt_data)
+
+
+def get_json_encoder(app: Flask) -> Type[json.JSONEncoder]:
+    """Get the JSON Encoder for the provided flask app
+
+    Starting with flask version 2.2 the flask application provides a
+    interface to register a custom JSON Encoder/Decoder under the json_provider_class.
+    As this interface is not compatible with the standard JSONEncoder, the `default`
+    method of the class is wrapped.
+
+    Lookup Order:
+      - app.json_encoder - For Flask < 2.2
+      - app.json_provider_class.default
+      - flask.json.provider.DefaultJSONProvider.default
+
+    """
+    if not HAS_JSON_PROVIDER:  # pragma: no cover
+        return app.json_encoder
+
+    # If the registered JSON provider does not implement a default classmethod
+    # use the method defined by the DefaultJSONProvider
+    default = getattr(app.json_provider_class, "default", DefaultJSONProvider.default)
+
+    class JSONEncoder(json.JSONEncoder):
+        def default(self, o: Any) -> Any:
+            return default(o)  # pragma: no cover
+
+    return JSONEncoder

flask_jwt_extended/tokens.py

@@ -3,6 +3,7 @@
 from datetime import timedelta
 from datetime import timezone
 from hmac import compare_digest
+from json import JSONEncoder
 from typing import Any
 from typing import Iterable
 from typing import List
@@ -13,7 +14,6 @@
 
 from flask_jwt_extended.exceptions import CSRFError
 from flask_jwt_extended.exceptions import JWTDecodeError
-from flask_jwt_extended.json_encoder import JSONEncoder
 from flask_jwt_extended.typing import ExpiresDelta
 
 

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py37,py38,py39,py310,pypy3.9,mypy,coverage,style,docs
+envlist = py{37,38,39,310}-{flask21,flask22},pypy3.9,mypy,coverage,style,docs
 
 [testenv]
 commands =