How do I pass through the "next" URL with Flask and Flask-login?

@timakro provides a neat solution.
If you want to handle a dynamic link such as

index/<user>

then using url_for(request.endpoint,**request.view_args) instead because request.endpoint will not contain the dynamic vairable info:

 @login_manager.unauthorized_handler
 def handle_needs_login():
     flash("You have to be logged in to access this page.")
     #instead of using request.path to prevent Open Redirect Vulnerability 
     next=url_for(request.endpoint,**request.view_args)
     return redirect(url_for('account.login', next=next))

the following code shall be changed to:

def redirect_dest(home):
    dest_url = request.args.get('next')
    if not dest_url:
        dest_url = url_for(home)
    return redirect(dest_url)

@app.route("/login", methods=["GET", "POST"])
def login():
    ...
    if user_is_logged_in:
        flash("Logged in!")
        return redirect_dest(home=anyViewFunctionYouWantToSendUser)
    else:
        flash("Sorry, but you could not log in.")
        return render_template("login.html")

Just in case someone is trying to pass through the “next” URL with Flask-Login but with Flask_Restful, the workaround I’ve been using is passing the “next” argument from the GET method to the POST method. With flask_restful the “next_page” argument is set to “None” after clicking on the Login Button in the login.html

login.html

...
<!-- next_page came from "render_template(next_page=request.args.get('next') ...)" in the get() function -->
<!-- And also from render_template('login.html', next_page=next_page) in the post() function -->
<form action="{{ url_for('login', next=next_page) }}" method="POST" >
    <div class="field">
        <div class="control">
            <input class="input is-large" type="email" name="email" placeholder="Your Email" autofocus="">
        </div>
    </div>

    <div class="field">
        <div class="control">
            <input class="input is-large" type="password" name="password" placeholder="Your Password">
        </div>
    </div>
    <div class="field">
        <label class="checkbox">
            <input type="checkbox" name="remember_me">
            Remember me
        </label>
    </div>
    <button class="button is-block is-info is-large is-fullwidth">Login</button>
</form>
...

auth.py

class Login(Resource):

    def get(self):
        if current_user.is_authenticated:
            return redirect(url_for('home'))

        headers = {'Content-Type': 'text/html'}

#1 -->  # Here I pass the "next_page" to login.html
        return make_response(render_template('login.html', next_page=request.args.get('next')), 200, headers)

    def post(self):
#2 -->  # After the user clicks the login button, I retrieve the next_page saved in the GET method
        next_page = request.args.get('next')

        if current_user.is_authenticated:
            return redirect(url_for('home'))

        # Check if account exists in the db
        existing_account = Account.objects(email=request.form.get('email')).first()

        # Only redirects when the URL is relative, which ensures that the redirect 
        # stays within the same site as the application.
        if existing_account:
            if existing_account.check_password(request.form.get('password')):
                login_user(existing_account, remember=request.form.get('remember_me'))

                if not next_page or url_parse(next_page).netloc != '':
                    return redirect(url_for('home'))

#3 -->          # Here I use the retrieved next_page argument
                return redirect(url_for(next_page))

        # Account not recognized
        flash('Please check your login details and try again.')
        headers = {'Content-Type': 'text/html'}

#4 -->  # I also pass the "next_page" here in case the user-provided data is wrong
        return make_response(render_template('login.html', next_page=next_page), 200, headers)

Out of all the above answers I didn’t find anything helpful for me.
But what I found, I will share with you..

In login.html just add the below code

<input
    type="hidden"
    name="next"
    value="{{ request.args.get('next', '') }}"
/>

And login definition changes as follows

@app.route("/login", methods=["GET", "POST"])
def login():
    if request.method == "POST":
        username = request.form.get("username")
        password = request.form.get("password")
        next_url = request.form.get("next")

        if username in users and users[username][1] == password:
            session["username"] = username
            if next_url:
                return redirect(next_url)
            return redirect(url_for("profile"))
    return render_template("login.html")

And This worked perfectly for me…

Thank you …

This is what worked for me, this is an addition to what @timakro and @Kurumi Tokisaki has provided in an earlier post.

@login_manager.unauthorized_handler
def handle_needs_login():
    return redirect(url_for('login', next_page=request.endpoint))

@app.route('/login/<next_page>', methods=['GET', 'POST'])
def login(next_page):
    if current_user.is_authenticated:
        return redirect(url_for(next_page))

    if is_a_successfull_login():
        redirect(url_for(next_page))

Simple Example

@app.route('/login', methods=['GET', 'POST'])
def login():
    // do your stuff
    next_page = request.form.get('next_page')
    # next_page either be 'http://localhost:5000/None or 'http://localhost:5000/some_endpoints
   return redirect(next_page) if 'None' not in next_page else redirect(url_for('default_action'))

Note

as Mentioned in Flask documentation
don’t forget to pass next_url in html

<input type="hidden" value="{{ request.args.get('next') }}" name="next_page" id="next_page"/>