python - Trailing slash in Flask route

Question

Take for example the following two routes.

app = Flask(__name__)

@app.route("/somewhere")
def no_trailing_slash():
    #case one

@app.route("/someplace/")
def with_trailing_slash():
    #case two

According to the docs the following is understood:

• In case one, a request for the route "/somewhere/" will return a 404 response. "/somewhere" is valid.

• In case two, "/someplace/" is valid and "/someplace" will redirect to "/someplace/"

The behavior I would like to see is the 'inverse' of the case two behavior. e.g. "/someplace/" will redirect to "/someplace" rather than the other way around. Is there a way to define a route to take on this behavior?

From my understanding, strict_slashes=False can be set on the route to get effectively the same behavior of case two in case one, but what I'd like to do is get the redirect behavior to always redirect to the URL without the trailing slash.

One solution I've thought of using would be using an error handler for 404's, something like this. (Not sure if this would even work)

@app.errorhandler(404)
def not_found(e):
    if request.path.endswith("/") and request.path[:-1] in all_endpoints:
        return redirect(request.path[:-1]), 302
    return render_template("404.html"), 404

But I'm wondering if there's a better solution, like a drop-in app configuration of some sort, similar to strict_slashes=False that I can apply globally. Maybe a blueprint or url rule?

Answer 1

You are on the right tracking with using strict_slashes, which you can configure on the Flask app itself. This will set the strict_slashes flag to False for every route that is created

app = Flask('my_app')
app.url_map.strict_slashes = False

Then you can use before_request to detect the trailing / for a redirect. Using before_request will allow you to not require special logic to be applied to each route individually

@app.before_request
def clear_trailing():
    from flask import redirect, request

    rp = request.path 
    if rp != '/' and rp.endswith('/'):
        return redirect(rp[:-1])