"No spec provided" error when trying to deliver swagger.json over HTTPS

Question

If I try to deliver the Swagger UI using Flask RestPlus over HTTPS, I see only the "No spec provided" error message at the root URL, and the full Swagger UI never loads. However, if I visit the API endpoints they return responses as expected.

Looking at the source HTML for the error page, I noticed that swagger.json was being fetched from http://myhost/ rather than https://myhost/

I've discovered exactly the same issue on the restplus Github issues

I've fixed my issue temporarily with the monkey-patch mentioned on that page. The Swagger UI loads, and looking at the HTML source I see that swagger.json is indeed fetched from https://myhost.

Why is this happening, and how can I fix it without the monkey-patching?

HTTPS is courtesy of Cloudflare's "flexible" HTTPS service.

My app is behind Nginx which is configured thus, and hasn't been causing any issues as far as I'm aware:

...
http {
  ...
  server {
    location / {
      charset UTF-8;
      try_files $uri @proxy_to_app;
    }
    location @proxy_to_app {
      charset UTF-8;
      proxy_intercept_errors on;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header X-Forwarded-Proto $scheme;
      proxy_set_header Host $http_host;
      proxy_redirect off;
      proxy_pass http://127.0.0.1:5000;
    }
  }
}

Answer 1

I have used below to get it worked. You can view the stable example in below link.

http://flask-restplus.readthedocs.io/en/stable/example.html

from werkzeug.contrib.fixers import ProxyFix
app = Flask(__name__)
app.wsgi_app = ProxyFix(app.wsgi_app)