Flask-Cors not working while using url_prefix in blueprints

I was using flask-cors for my flask application which failed to enable CORS for blueprints where blueprints were registered along with url_prefix as their property. However, when I removed url_prefix and manually added prefix in blueprints, CORS seemed to be working fine.

Example

This code works properly

from flask import Flask, make_response
from flask_cors import CORS

from tracer.blueprints.auth import app as auth_blueprint
from tracer.blueprints.url import app as url_blueprint

app = Flask(__name__)
CORS(app)

app.register_blueprint(auth_blueprint)
app.register_blueprint(url_blueprint)

if __name__ == '__main__':
    app.run(host='0.0.0.0')

This code doesn’t allow CORS

.
.
app.register_blueprint(auth_blueprint, url_prefix='/auth')
app.register_blueprint(url_blueprint, url_prefix='/url')
.
.

[aalokrmb]

This issue has to close now. A lot of solutions have come forward.

yup, we can close it, thanks to everyone for your help and suggestions, However, the @gianlukk994 solution worked fine for me. thanks, @gianlukk994.

[PhilipRead]

Just thought I’d throw my perspective. I was having the same issue and I could not for the life of me understand why some calls were getting CORS errors. Upon closing inspection I realized that the ‘bad’ urls where returning 308s. After looking at the Location header I realized that it was failing because my blueprint routes for those failing endpoints had trailing slashes in them. Once I took them out it all worked fine. Why Axios or Chrome can’t just process the redirect instead of failing with a misleading ‘CORS’ issue is beyond me.

Anyway, here is an example of what I mean:

bp = Blueprint('api', __name__, url_prefix = '/api')

# @bp.route('some-resources/', methods = ('GET', 'POST')) # Wrong
@bp.route('some-resources', methods = ('GET', 'POST')) # Right!
def someResources():
...