`click.get_current_context()` returns `None` after reload

[reubano]

Following the guidelines in #3552, click.get_current_context() returns an empty ctx when the Flask app reloads (this is due to the thread switching).

app.py

from threading import get_native_id
from click import get_current_context

def create_app(*args, **kwargs):
    ctx = get_current_context(silent=True)
    print(get_native_id(), ctx)
    script_info = ctx.obj if ctx else None
    ...

manage.py

import click

from flask.cli import FlaskGroup, pass_script_info

from app import create_app


@click.group(cls=FlaskGroup, create_app=create_app)
@click.option("-m", "--config-mode", default="Development")
@pass_script_info
def manager(script_info, config_mode=None, **kwargs):
    script_info.config_mode = config_mode


if __name__ == "__main__":
    manager()

$ python manage.py run -p 5001
 * Environment: development
 * Debug mode: on
2537498, <click.core.Context object at 0x104a98490>
 * Running on http://127.0.0.1:5001/ (Press CTRL+C to quit)
 * Restarting with stat
2537262, None
 * Debugger is active!
 * Debugger PIN: 271-523-819

Notice how after Restarting with stat, ctx is now None.

Since passing script_info to the app factory was deprecated, the work-a-round should also work on app restarts just like the deprecated workflow does.

Environment:

• Python version: 3.9.10
• Flask version: 2.0.3

[davidism]

I don't understand the issue being described. A restart restarts the entire process, state was never preserved between restarts. When opening an issue, be sure to include enough detail so that we can accurately understand and reproduce the issue.

[reubano]

To clarify, this is app reloading, not manual restarting.

[davidism]

Yes, app reloading restarts the process. Flask never attempted or enabled persisting state between reloads.

[reubano]

from click import get_current_context

def create_app(*args, **kwargs):
    ctx = get_current_context(silent=True)
    print(ctx)

python manage.py run -p 5001
 * Environment: development
 * Debug mode: on
<click.core.Context object at 0x104a98490>
 * Running on http://127.0.0.1:5001/ (Press CTRL+C to quit)
 * Restarting with stat
None
 * Debugger is active!
 * Debugger PIN: 271-523-819

Notice how after Restarting with stat, ctx is now None.

[reubano]

https://pypi.org/project/manage.py/.... basically Django style manage commands. I use manage instead of flask or python manage.py

[davidism]

That library was last released in 2015, and the GitHub repo it links to doesn't exist. It's not part of Flask.

[davidism]

This is because the app is lazy-loaded, which happens in a separate thread. Click's context is thread-local, so the thread that calls create_app doesn't have access to the context. You can continue using the context by disabling lazy loading, at the expense of the reloader not handling syntax errors. flask run --eager-loading

Part of the point of removing script_info is that it's essentially an internal part of the Flask CLI, not something that can be relied on, since it won't be available in production. If you find yourself needing it, reconsider the design of your app factory.