X-HTTP-Method-Override in Flask's Python Web server

I'm learning HTTP and I try to learn how different headers work. I want to implement a simple HTTP server using Flask and Python just to test theX-HTTP-Method-Override header.

My code:

class HTTPMethodOverrideMiddleware(object):
    allowed_methods = frozenset(
        ["GET", "HEAD", "POST", "DELETE", "PUT", "PATCH", "OPTIONS"]
    )
    bodyless_methods = frozenset(["GET", "HEAD", "OPTIONS", "DELETE"])

    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        method = environ.get("HTTP_X_HTTP_METHOD_OVERRIDE", "").upper()
        if method in self.allowed_methods:
            environ["REQUEST_METHOD"] = method
        if method in self.bodyless_methods:
            environ["CONTENT_LENGTH"] = "0"
        return self.app(environ, start_response)


from flask import Flask, request

app = Flask(__name__)


@app.route("/")
def index():
    return request.method


app.wsgi_app = HTTPMethodOverrideMiddleware(app.wsgi_app)
app.run(host="0.0.0.0", port=9090)

When I'm sending this curl request: curl -X GET "http://127.0.0.1:9090" server returns GET, which is OK, but with this: curl -X GET "http://127.0.0.1:9090" --header "X-HTTP-Method-Override : POST" it still shows GET instead of POST.

What is wrong? The code or curl?

The issue is in both code and curl command.

You need to allow the methods on the route, like this:

@app.route("/", methods = ["GET", "POST"])
def index():
  return request.method

This will allow GET and POST methods on the route, enabling you to execute the following commands:

curl -X GET "http://127.0.0.1:9090" --header "X-HTTP-Method-Override: POST"

curl -X POST "http://127.0.0.1:9090" --header "X-HTTP-Method-Override: GET"

You had spaces between : in the --header which caused it not parsing corrently.