python – Serving a front end created with create-react-app with Flask-ThrowExceptions

Exception or error:

I have a Flask back-end with API routes which are accessed by a React single page application created using create-react-app. When using the create-react-app dev server, my Flask back end works.

I would like to serve the built (using npm run build) static React app from my Flask server. Building the React app leads to the following directory structure:

- build
  - static
    - css
        - style.[crypto].css
        - style.[crypto].css.map
    - js
        - main.[crypto].js
        - main.[crypto].js.map
  - index.html
  - service-worker.js
  - [more meta files]

By [crypto], I mean the randomly generated strings generated at build time.

Having received the index.html file, the browser then makes the following requests:

- GET /static/css/main.[crypto].css
- GET /static/css/main.[crypto].css
- GET /service-worker.js

How should I serve these files? I came up with this:

from flask import Blueprint, send_from_directory

static = Blueprint('static', __name__)

@static.route('/')
def serve_static_index():
    return send_from_directory('../client/build/', 'index.html')

@static.route('/static/<path:path>') # serve whatever the client requested in the static folder
def serve_static(path):
    return send_from_directory('../client/build/static/', path)

@static.route('/service-worker.js')
def serve_worker():
    return send_from_directory('../client/build/', 'service-worker.js')

This way, the static assets are successfully served.

On the other hand, I could incorporate this with the built-in Flask static utilities. But I do not understand how to configure this.

Is my solution robust enough? Is there a way to use built-in Flask features to serve these assets? Is there a better way to use create-react-app?

How to solve:
import os
from flask import Flask, send_from_directory

app = Flask(__name__, static_folder='react_app/build')

# Serve React App
@app.route('/', defaults={'path': ''})
@app.route('/<path:path>')
def serve(path):
    if path != "" and os.path.exists(app.static_folder + '/' + path):
        return send_from_directory(app.static_folder, path)
    else:
        return send_from_directory(app.static_folder, 'index.html')


if __name__ == '__main__':
    app.run(use_reloader=True, port=5000, threaded=True)

Thats what I ended up with. So bascially catch all routes, test if the path is a file => send file => else send the index.html. That way you can reload the react app from any route you wish and it does not break.

Answer:

First do npm run build to build the static production files as mentioned by you above

from flask import Flask, render_template

app = Flask(__name__, static_folder="build/static", template_folder="build")

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

print('Starting Flask!')

app.debug=True
app.run(host='0.0.0.0')

Unfortunately, I don’t think you can get it work with the development hot-reload.

Answer:

The accepted answer does not work for me. I have used

import os

from flask import Flask, send_from_directory, jsonify, render_template, request

from server.landing import landing as landing_bp
from server.api import api as api_bp

app = Flask(__name__, static_folder="../client/build")
app.register_blueprint(landing_bp, url_prefix="/landing")
app.register_blueprint(api_bp, url_prefix="/api/v1")


@app.route("/")
def serve():
    """serves React App"""
    return send_from_directory(app.static_folder, "index.html")


@app.route("/<path:path>")
def static_proxy(path):
    """static folder serve"""
    file_name = path.split("/")[-1]
    dir_name = os.path.join(app.static_folder, "/".join(path.split("/")[:-1]))
    return send_from_directory(dir_name, file_name)


@app.errorhandler(404)
def handle_404(e):
    if request.path.startswith("/api/"):
        return jsonify(message="Resource not found"), 404
    return send_from_directory(app.static_folder, "index.html")


@app.errorhandler(405)
def handle_405(e):
    if request.path.startswith("/api/"):
        return jsonify(message="Mehtod not allowed"), 405
    return e


Answer:

A working solution here.
Ever thought why we need two separate folders for static and templates. To segregate the mess, right?
But, it’s a problem with the production build since it has one folder for both static and templates type of files and all dependencies are linked like that.

The build folder will be served if you consider it both static and templates.

Use something like this

from flask import Flask, render_template

app = Flask(__name__, static_url_path='',
                  static_folder='build',
                  template_folder='build')

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

Your flask app will run fine.

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