[MIDDLEWARE] middleware executed many times

从 issue 中所示的 GraphQLView.as_view 配置和 DummyMiddleware.resolve 开始，然后使用 hello 查询、列表查询和 logout mutation 重现该行为。比较中间件的调用次数，并在确定由哪个组件负责之前，确定预期的单次执行行为。

Hi there, I'm using flask-graphql in a project and got into a question/issue I don't have many clues. I'm using middlewares; this is the minimum example:

from flask import Flask, request
from flask_graphql import GraphQLView
from graphene import Field, ObjectType, Schema, String, relay


class Hello(ObjectType):
    message = String()


class Query(ObjectType):
    hello = Field(Hello)

    def resolve_hello(self, info):
        return Hello(message="Hi there")

class DummyMiddleware(object):
    def resolve(self, next, root, info, **kwargs):
        print("DummyMiddleware")
        return next(root, info, **kwargs)


dummy_middleware = DummyMiddleware()
schema = Schema(query=Query)

app = Flask(__name__)
app.add_url_rule('/graphql', view_func=GraphQLView.as_view('graphql',
                                                      schema=schema,
                                                      graphiql=True,
                                                      middleware=[dummy_middleware]))

if __name__ == "__main__":
    app.run(host='0.0.0.0', threaded=True)

(The problem happens no matter the version; the problem also happens when launching the wsgi app with gunicorn).

If I query "hello()", the "DummyMiddleware" will appear twice. If I query a list of elements, the middleware is executed lots of time, twice per element it seems.
For a query this is just a problem of performance, but in a Logout() mutation what happens is:

• 1st time - the authenticated request is valid, so "logout()" deletes the token
• 2nd time - the authenticated request is not valid (because the token has been deleted), so it returns an error

Is there anything wrong in my approach to middlewares? I'm not sure which part is responsible (flask, graphql, my configuration...). Any hint would be appreciated.