Having issues using Flask-JWT-Extended with Flask-Restful

Question

I'm building an API using Flask-Restful following the steps from the book "Python API Fundamentals". The problem I'm having is that I'm unable to get a token. My code which is an edited replica of that which is in the book is throwing the following error whenever I test it on Postman

127.0.0.1 - - [01/Aug/2022 13:26:49] "POST /token HTTP/1.1" 500 -
Traceback (most recent call last):
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask\app.py", line 2091, in __call__
    return self.wsgi_app(environ, start_response)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask\app.py", line 2076, in wsgi_app
    response = self.handle_exception(e)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask_restful\__init__.py", line 271, in error_router
    return original_handler(e)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask\app.py", line 2073, in wsgi_app
    response = self.full_dispatch_request()
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask\app.py", line 1519, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask_restful\__init__.py", line 271, in error_router
    return original_handler(e)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask\app.py", line 1517, in full_dispatch_request
    rv = self.dispatch_request()
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask\app.py", line 1503, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask_restful\__init__.py", line 467, in wrapper
    resp = resource(*args, **kwargs)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask\views.py", line 84, in view
    return current_app.ensure_sync(self.dispatch_request)(*args, **kwargs)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask_restful\__init__.py", line 582, in dispatch_request
    resp = meth(*args, **kwargs)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\smilecook\resources\token.py", line 24, in post
    access_token = create_access_token(identity=user.id)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask_jwt_extended\utils.py", line 157, in create_access_token
    return jwt_manager._create_access_token(identity, fresh, expires_delta, user_claims)
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask_jwt_extended\jwt_manager.py", line 469, in _create_access_token
    access_token = encode_access_token(
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask_jwt_extended\tokens.py", line 76, in encode_access_token
    return _encode_jwt(token_data, expires_delta, secret, algorithm,
  File "C:\Users\TARI\Documents\GitHub\understand_api_development_with_python\basic-api\venv\Lib\site-packages\flask_jwt_extended\tokens.py", line 31, in _encode_jwt
    json_encoder=json_encoder).decode('utf-8')
AttributeError: 'str' object has no attribute 'decode'

Here's my requirements.txt

Flask==2.1.3
Flask-RESTful==0.3.9
httpie==3.2.1
Flask-SQLAlchemy==2.5.1
Flask-Migrate==3.1.0
psycopg2-binary==2.9.3
passlib==1.7.4
Flask-JWT-Extended==3.20.0
Werkzeug==2.0

and the codes that I think is causing the issue

from http import HTTPStatus
from flask import request
from flask_restful import Resource
from flask_jwt_extended import create_access_token

from utils import check_password
from models.user import User


class TokenResource(Resource):

    def post(self):

        json_data = request.get_json()

        email = json_data.get('email')
        password = json_data.get('password')

        user = User.get_by_email(email=email)

        if not user or not check_password(password, user.password):
            return {'message': 'username or password is incorrect'}, HTTPStatus.UNAUTHORIZED

        access_token = create_access_token(identity=user.id)

        return {'access_token': access_token}, HTTPStatus.OK

from flask import request
from flask_restful import Resource
from flask_jwt_extended import jwt_optional, get_jwt_identity
from http import HTTPStatus

from utils import hash_password
from models.user import User


class UserListResource(Resource):
    def post(self):
        json_data = request.get_json()

        username = json_data.get('username')
        email = json_data.get('email')
        non_hash_password = json_data.get('password')

        if User.get_by_username(username):
            return {'message': 'username already used'}, HTTPStatus.BAD_REQUEST

        if User.get_by_email(email):
            return {'message': 'email already used'}, HTTPStatus.BAD_REQUEST

        password = hash_password(non_hash_password)

        user = User(
            username=username,
            email=email,
            password=password
        )

        user.save()

        data = {
            'id': user.id,
            'username': user.username,
            'email': user.email
        }

        return data, HTTPStatus.CREATED


class UserResource(Resource):

    @jwt_optional
    def get(self, username):

        user = User.get_by_username(username=username)

        if user is None:
            return {'message': 'user not found'}, HTTPStatus.NOT_FOUND

        current_user = get_jwt_identity()

        if current_user == user.id:
            data = {
                'id': user.id,
                'username': user.username,
                'email': user.email,
            }

        else:
            data = {
                'id': user.id,
                'username': user.username,
            }

        return data, HTTPStatus.OK

from flask import Flask
from flask_migrate import Migrate
from flask_restful import Api

from config import Config
from extensions import db, jwt


from resources.user import UserListResource, UserResource
from resources.token import TokenResource
from resources.recipe import RecipeListResource, RecipeResource, RecipePublishResource


def create_app():
    app = Flask(__name__)
    app.config.from_object(Config)

    register_extensions(app)
    register_resources(app)

    return app


def register_extensions(app):
    db.init_app(app)
    migrate = Migrate(app, db)
    jwt.init_app(app)


def register_resources(app):
    api = Api(app)

    api.add_resource(UserListResource, '/users')
    api.add_resource(UserResource, '/users/<string:username>')

    api.add_resource(TokenResource, '/token')

    api.add_resource(RecipeListResource, '/recipes')
    api.add_resource(RecipeResource, '/recipes/<int:recipe_id>')
    api.add_resource(RecipePublishResource, '/recipes/<int:recipe_id>/publish')


if __name__ == '__main__':
    app = create_app()
    app.run()

the results of pip freeze

alembic==1.8.1
aniso8601==9.0.1
certifi==2022.6.15
charset-normalizer==2.1.0
click==8.1.3
colorama==0.4.5
commonmark==0.9.1
defusedxml==0.7.1
Flask==2.1.3
Flask-JWT-Extended==3.20.0
Flask-Migrate==3.1.0
Flask-RESTful==0.3.9
Flask-SQLAlchemy==2.5.1
greenlet==1.1.2
httpie==3.2.1
idna==3.3
itsdangerous==2.1.2
Jinja2==3.1.2
Mako==1.2.1
MarkupSafe==2.1.1
multidict==6.0.2
passlib==1.7.4
psycopg2-binary==2.9.3
Pygments==2.12.0
PyJWT==2.4.0
PySocks==1.7.1
pytz==2022.1
requests==2.28.1
requests-toolbelt==0.9.1
rich==12.5.1
six==1.16.0
SQLAlchemy==1.4.39
urllib3==1.26.11
Werkzeug==2.0.0

Answer 1

This is happening because you have a newer version of PyJWT with an older version of flask jwt extended that are incompatible. Upgrading flask jwt extended to at least 3.25.0 should fix the issue. If you upgrade to the 4.xx version of flask jwt extended, make sure to read over the breaking changes here: https://flask-jwt-extended.readthedocs.io/en/stable/v4_upgrade_guide/