White-list the HTTP methods on each route

[nggit]

In some frameworks like Flask, you can white-list request methods with the methods parameter in the route decorator:

# Flask
@app.route('/login', methods=['GET', 'POST'])
def hello_world():
    return 'Hello, World!'

Tremolo doesn't support that but it allows us to do something similar.

Since tremolo supports arbritrary parameters in handlers, you can just put methods in handlers as follows:

@app.route('/hello')
async def hello_world(methods=[b'GET', b'POST'], **server):
    return b'Hello, World!'

Then the methods parameter will be available in request.context.options so that we can process it in the response middleware:

from tremolo.exceptions import MethodNotAllowed

@app.on_response
async def response_middleware(request, **server):
    ctx = request.context
    # alternatives:
    # ctx = request.ctx

    if 'methods' in ctx.options and request.method not in ctx.options['methods']:
        # exiting...
        raise MethodNotAllowed
        # return b'Request method %s is not allowed!' % request.method