How do I handle login in flask with multiple blueprints?

Question

I have multiple blueprints that needs to be integrated into a single app. I'm using flask-login to handle logins. However I'm confused on how to handle the LoginManager() and the .user_loader for my blueprints.

This is my current file structure.

system/
     run.py
     config.py
     app/
        __init__.py
        models.py
        views/
             blueprint1.py
             blueprint2.py
        static/
        templates/
              <templates>

What's the correct way to implement them? Do I just call them at the __init__.py and import the login manager variable at the blueprints? or Do I need to call them individually in the blueprints?

Hopefully I'm able to portray the question clearly. Thank you for reading and answering

Answer 1

The documentation is really unclear and I will put down what I come up with after spending some time researching.

You only need to define login_manager once in the flask app.py and init_app. Then at each blueprint, from flask_login import login_required and use the @login_required as usual. Turns out it can be used without stating the login_manager

Code example (app with single blueprint)

app.py

import flask
from flask import redirect, url_for
import flask_login

from blueprint.secret import secret_bp
from model.user import User

login_manager = flask_login.LoginManager()

app = flask.Flask(__name__)
app.register_blueprint(secret_bp, url_prefix="/secret")

login_manager.init_app(app)

@login_manager.user_loader
def load_user(user_id):
    return User.get(user_id)

@app.route('/login', methods=['GET', 'POST'])
def login():
    if flask.request.method == "GET":
        return "<form action='/login' method='POST'><input type='text' name='user'><button type='submit'>Submit</button></form>"

    user = flask.request.form.get('user')
    if user == "user":
        # Login and validate the user.
        # user should be an instance of your `User` class
        flask_login.login_user(user)

        flask.flash('Logged in successfully.')

        return flask.redirect(next or flask.url_for('index'))
    return flask.redirect(flask.url_for('login'))

@app.route('/admin')
def admin():
    return "Admin page"

@login_manager.unauthorized_handler
def unauthorized():
    # do stuff
    return redirect(url_for('login'))

secret.py

from flask import Blueprint, render_template, abort
from jinja2 import TemplateNotFound
from flask_login import login_required

secret_bp = Blueprint('secret', __name__,
                        template_folder='templates')

@secret_bp.route('/noneed')
def no_need():
    return "You can see this without login."

@secret_bp.route('/needlogin')
@login_required
def show():
    return "can't see this if not login"

As expected, /secret/noneed can be access without login and /secret/needlogin will redirect you with the function stated with @unauthorized_handler.