--help flag does not work with QUART_APP envvar and create_app factory

首先阅读 quart/cli.py 中 Quart CLI 的应用加载路径，尤其是它如何读取 QUART_APP 并处理顶层 --help 选项。使用通过 QUART_APP 选择的 create_app 工厂复现问题，然后与 --app 进行比较。当 QUART_APP=run quart --help 能在没有导入错误的情况下显示帮助，且报告中的子命令仍可正常运行时，即为完成。

When using a create_app() factory function, the --help flag does not work with QUART_APP envvar but does work with --app flag. All other quart subcommands work such as 'run'.

Minimal example

Layout

.
├── init.py
├── run.py
└── server.py

server.py

from quart import Quart

def create_app(mode='Development'):
    app = Quart(__name__)
    print("hello from create_app")
    return app

run.py

from .server import create_app

def main():
    app = create_app()
    app.run()


if __name__ == "__main__":
    app.run()

Expected behaviour

% quart --app=run --help
hello from create_app
Usage: quart [OPTIONS] COMMAND [ARGS]...

  A general utility script for Quart applications. An application to load must
  be given with the '--app' option, 'QUART_APP' environment variable, or with
  an 'app.py' file in the current directory.

Options:
  -e, --env-file FILE   Load environment variables from this file. python-
                        dotenv must be installed.
  -A, --app IMPORT      The QUART application or factory function to load, in
                        the form 'module:name'. Module can be a dotted import
                        or file path. Name is not required if it is 'app',
                        'application', 'create_app', or 'make_app', and can be
                        'name(args)' to pass arguments.
  --debug / --no-debug  Set 'app.debug' separately from '--env'.
  --version             Show the Quart version
  --help                Show this message and exit.

Commands:
  routes  Show the routes for the app.
  run     Run a development server.
  shell   Run a shell in the app context.

% quart --app=run run       
hello from create_app
 * Serving Quart app 'quarttest.server'
 * Debug mode: False
 * Please use an ASGI server (e.g. Hypercorn) directly in production
 * Running on http://127.0.0.1:5000 (CTRL + C to quit)

Incorrect behaviour

% QUART_APP=run quart --help
Error: While importing 'quarttest.app', an ImportError was raised:

Traceback (most recent call last):
  File "/Users/erikmelander/kod/quarttest/venv/lib/python3.11/site-packages/quart/cli.py", line 186, in locate_app
    module = import_module(module_name)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/[email protected]/3.11.4_1/Frameworks/Python.framework/Versions/3.11/lib/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap>", line 1204, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1176, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1140, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'quarttest.app'


Usage: quart [OPTIONS] COMMAND [ARGS]...

  A general utility script for Quart applications. An application to load must
  be given with the '--app' option, 'QUART_APP' environment variable, or with
  an 'app.py' file in the current directory.

Options:
  -e, --env-file FILE   Load environment variables from this file. python-
                        dotenv must be installed.
  -A, --app IMPORT      The QUART application or factory function to load, in
                        the form 'module:name'. Module can be a dotted import
                        or file path. Name is not required if it is 'app',
                        'application', 'create_app', or 'make_app', and can be
                        'name(args)' to pass arguments.
  --debug / --no-debug  Set 'app.debug' separately from '--env'.
  --version             Show the Quart version
  --help                Show this message and exit.

Commands:
  routes  Show the routes for the app.
  run     Run a development server.
  shell   Run a shell in the app context.

% QUART_APP=run quart run   
hello from create_app
 * Serving Quart app 'quarttest.server'
 * Debug mode: False
 * Please use an ASGI server (e.g. Hypercorn) directly in production
 * Running on http://127.0.0.1:5000 (CTRL + C to quit)

Environment:

• Python version: 3.11
• Quart version: 0.22.0