Flask and React routing

Question

I'm building the Flask app with React, I ended up having a problem with routing.

The backend is responsible to be an API, hence some routes look like:

@app.route('/api/v1/do-something/', methods=["GET"])
def do_something():
    return something()

and the main route which leads to the React:

@app.route('/')
def index():
    return render_template('index.html')

I'm using react-router in the React app, everything works fine, react-router takes me to /something and I get the rendered view, but when I refresh the page on /something then Flask app takes care of this call and I get Not Found error.

What is the best solution? I was thinking about redirecting all calls which are not calling /api/v1/... to / it's not ideal as I will get back the home page of my app, not rendered React view.

Solution 1

We used catch-all URLs for this.

from flask import Flask
app = Flask(__name__)

@app.route('/', defaults={'path': ''})
@app.route('/<path:path>')
def catch_all(path):
    return 'You want path: %s' % path

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

You can also go an extra mile and reuse the Flask routing system to match path to the same routes as client so you can embed the data client will need as JSON inside the HTML response.

Solution 2

Maybe as extension to the answers before. This solved the problem for me:

from flask import send_from_directory

@app.route('/', defaults={'path': ''})
@app.route('/<path:path>')
def serve(path):
     path_dir = os.path.abspath("../build") #path react build
     if path != "" and os.path.exists(os.path.join(path_dir, path)):
         return send_from_directory(os.path.join(path_dir), path)
     else:
         return send_from_directory(os.path.join(path_dir),'index.html')

Solution 3

For some reason, the catch-all URLs did not work for me. I found that using the flask 404 handler results in the exact same thing. It sees the url and passes it down to react where your router will handle it.

@app.errorhandler(404)   
def not_found(e):   
  return app.send_static_file('index.html')

Comments

[shangsunset]

if all the routes will be directed to catch all function, how would you separate backend api routes and react routes when i do a ajax request call from front end?

[Dan Abramov]

@shangyeshen Register API routes before catch-all so they have precedence.

[juanitogan]

Is there a complete example of this somewhere? The code here doesn't do any index rendering like the example above and I have been unable to combine the two in a way that works.

[juanitogan]

Found it. I couldn't get @app.route('/<path:path>') to match on anything until I figured out the poorly documented Flask parameters. Setting static_url_path="" is bad. I ended up with static_url_path="/public", static_folder="../public". Then I return a static: return app.send_static_file("index.html") with hard-coded "/public/..." urls. Also, look at: reddit.com/r/reactjs/comments/42pn95/reactrouter_and_flask_4‌​04 (not me).

[Jason]

This is the solution I used for a while until I needed to break my bundle into parts using React.lazy. React.lazy wants to get the bundle parts from the path instead of the static directory that flask is using. Any ideas on that?

[logeekal]

Hello @Jason, what is the issues your are getting in React.lazy. We are trying to go down this route and I am researching all pros and cons this approach. Thank you.

[TheDiveO]

Can't you replace the empty os.path.join(path_dir) with just a plain path_dir?

[Sundios]

This works great! thanks for sharing this!