A Flask app holds a reference to itself

from flask import Flask
import objgraph

def make_app():
    app = Flask(__name__)

    @app.route('/')
    def hello_world():
        return 'Hello, World!'

    return app

def test():
    myapp = make_app()
    objgraph.show_backrefs([myapp], filename='backrefs.png', max_depth=6)

test()

Here’s what the produced reference graph looks like:

Is it the intended behavior? In our library a Flask app is created dynamically in a closure, and as a result it retains anything else that was created in that closure. We work around this by having a trampoline function and passing heavy objects as weakrefs, but it was still unexpected.

Environment

• Python version: 3.7.5
• Flask version: 1.1.2
• Werkzeug version: 1.0.1

[jab]

@davidism and I discussed further and agreed to accept a fix for this, so I just merged #3762 after making some cleanups.

Thank you for the issue report and the PR!

[davidism]

The test that you added is now preventing me from implementing other legitimate things. I want to have a self.json = JSONProvider(self) assignment, but the test still fails. Composition like this is a very common pattern, and it would be meaningless to do it without the self in this case. I’m very likely to remove the test to support that.