Python: `FlaskApp` instances do not reliably track subclasses

[UpsideDownFoxxo]

I was running a set of queries on the CTFd repository, and got suspiciously few results for endpoints. After some experimenting I found out that they subclass Flask, which the current query for FlaskApp::instance() does not seem to track.

Minimal example:

Query:

import python

import semmle.python.frameworks.Flask
import semmle.python.ApiGraphs


from API::Node node
where Flask::FlaskApp::instance() = node
select node

Python:

from flask import Flask


class Sub(Flask):
    def __init__(self, *args, **kwargs):
        Flask.__init__(self, *args, **kwargs)


app = Sub(__name__)


@app.route("/")
def hello():
    return "world"

CodeQL is not able to identify Sub as a Flask app, which means the route setup for hello cannot be detected as well.

Adding .getASubclass*() to FlaskApp::instance() would probably fix this. If this can be overridden without changes to the library I am open to suggestions, my knowledge of the QL modules is not that great as of now.

[mbg]

Hi @UpsideDownFoxxo! Thanks for opening this issue. I have passed this on to the team that looks after our Python queries for them to have a look.