Better exception handling when env vars are missing for flask CLI #2741
Description
Expected Behavior
As there is the support for lazy loading the app, when running flask CLI without providing the proper environment variables we must see a better warning instead of raw exception.
Tell us what should happen.
we should see a better warning or message pointing to the problem
# there is no FLASK_APP env var
$ flask --help
WARNING: You need to define the app e.g: `export FLASK_APP=app.py`Actual Behavior
Tell us what happens instead.
we see traceback before the help message
# there is no FLASK_APP env var
$ flask --help Sat 28 Apr 2018 01:25:50 PM -03
Traceback (most recent call last):
File "~Projects/personal/flasgger/venv/lib/python3.6/site-packages/flask/cli.py", line 235, in locate_app
__import__(module_name)
ModuleNotFoundError: No module named 'app'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "~/Projects/personal/flasgger/venv/lib/python3.6/site-packages/flask/cli.py", line 529, in list_commands
rv.update(info.load_app().cli.list_commands(ctx))
File "~/Projects/personal/flasgger/venv/lib/python3.6/site-packages/flask/cli.py", line 372, in load_app
app = locate_app(self, import_name, name)
File "~/Projects/personal/flasgger/venv/lib/python3.6/site-packages/flask/cli.py", line 246, in locate_app
'Could not import "{name}".'.format(name=module_name)
flask.cli.NoAppException: Could not import "app".
Usage: flask [OPTIONS] COMMAND [ARGS]...
A general utility script for Flask applications.
Provides commands from Flask, extensions, and the application. Loads the
application defined in the FLASK_APP environment variable, or from a
wsgi.py file. Setting the FLASK_ENV environment variable to 'development'
will enable debug mode.
$ export FLASK_APP=hello.py
$ export FLASK_ENV=development
$ flask run
Options:
--version Show the flask version
--help Show this message and exit.
Commands:
routes Show the routes for the app.
run Runs a development server.
shell Runs a shell in the app context.
The same happens to run
$ flask run 429ms Sat 28 Apr 2018 01:32:48 PM -03
* Serving Flask app "app.py"
* Environment: production
WARNING: Do not use the development server in a production environment.
Use a production WSGI server instead.
* Debug mode: off
Usage: flask run [OPTIONS]
Error: Could not import "app".The Error: Could not import "app". could include WARNING: You need to define the app e.g: export FLASK_APP=app.py
Suggestion
We could check the existence of FLASK_APP envvar before running any of the commands in the Group Cli, if FLASK_APP does not exist the dispatch of commands never happens.
Environment
- Python version: 3.6.0
- Flask version: Flask==1.0
- Werkzeug version: Werkzeug==0.14.1
- Click: click==6.7