Don't require FLASK_APP to have .py extension

[bcongdon]

Addresses #2377. The simplest way that I found to do this was to just patch the find_default_import_path method to check if there's a file with the .py extension.

Worked in all of my testing. 🙂

[davidism]

Thanks! This is sort of the opposite direction of what I was imagining though. For example, a package that's not installed still requires FLASK_APP=myapp/__init__ when it should be importable as myapp because the current directory is on the PYTHONPATH.

[bcongdon]

Ah, I see. I updated the method to append the sys path if the referenced FLASK_APP is a directory. That should cover both the case where FLASK_APP=myapp and FLASK_APP=/path/to/myapp (where myapp is a module that contains a Flask app)

[davidism]

A friend pointed out that FLASK_APP=module flask run already works without the .py. So now I'm trying to figure out why that's importable but FLASK_APP=package isn't.

[pachewise]

@davidism wouldn't it hinge on os.path.isfile() behavior? In that case, don't see how FLASK_APP=module would work unless os.path doesn't care about file extensions...

[davidism]

Because the current directory is already inserted into sys.path.

[davidism]

Thanks for working on this. I ended up fixing this in #2414 by dropping the .py requirement rather than handling directories differently.