What is the recommended way to distinguish between dev and test without FLASK_ENV?

[jace]

Since FLASK_ENV is now deprecated, the three environments it previously supported, production, development and testing, have reduced to two: debug mode (with FLASK_DEBUG=1 or --debug/--debugger) and non-debug mode.

There doesn't seem to be a way to signal a test environment apart from setting app.config['TESTING'] = True in an app fixture, which happens during pytest runtime rather than import and init.

Is there a recommended way to signal a test environment from env vars?

[davidism]

The tutorial describes the application factory pattern https://flask.palletsprojects.com/en/2.2.x/tutorial/factory/ and how it's used in tests https://flask.palletsprojects.com/en/2.2.x/tutorial/tests/.

[jace]

This is a runtime flag though. My apps dropped the factory init pattern back in 2017 because it was so much pain fighting the extension ecosystem. For example, we had to write a wrapper for Flask-Alembic (which predated Flask-Migrate) to add an additional CLI parameter for specifying the environment, but it wouldn't reflect in the CLI documentation and had to be explained in the README.

Using FLASK_ENV has been great because the environment is well established at module import time. The interim fix for our code appears to be replacing FLASK_ENV with something like an APP_ENV so that Flask stops complaining about it. I don't like this because it will cause another drift from convention and future pain.

It'll be nice to have an unambiguous indicator of a testing environment at startup that the Flask ecosystem agrees on, the way FLASK_DEBUG now exists for the debugging environment.