Reloader doesn't add ".exe" to file on Windows

[peppobon]

if I run a flask app under 0.15.5 with
FLASK_ENV=development
the dev server throws an error.

With FLASK_ENV=production the server starts ok

After reinstalling 0.15.4 the same app works ok (both in dev and prod mode).

Windows/py3.6.7/pipenv

Kind regards

[ad-65]

Same issue using Flask 1.1.1/Werkzeug 0.15.5 on Windows 10, python 2.7.16, in a virtual environment. Looks like this: pallets/flask#1829 but it was fixed a long time ago.

[Foknetics]

Noticed this with the release of 0.15.5 as well with an application factory pattern, executing from Windows 10, Python 3.6.2, Flask 1.0.3, via Powershell. Created an example repo here. The change seems to be caused by the function _get_args_for_reloading() in _reloader.py

in 0.15.4 pymodule (line 108) gets set to .flask from the += "." + name which strips down to just flask in rv.

in 0.15.5 pymodule (line 109) gets set to C:\Users\conno\Desktop\werk_ex\venv\Scripts\flask, which strips to the same thing in rv
if os.path.isfile(py_script): (line 100) evaluating to false is really what causes the change from an execution perspective between the two versions.

[davidism]

I can't reproduce this. I have Flask 1.1.1 and Werkzeug 0.15.5, and tried flask run with the reloader in cmd and powershell, and both worked as expected.

[ad-65]

I tried this again on another Windows 10 machine with a system install of Python 2.7.15 (32-bit) and Python 3.7.2 (32-bit). The following steps (in powershell) reproduce the behavior for me. FLASK_ENV=production works fine, FLASK_ENV=development causes the error.

mkdir C:\Temp\flask_error
cd C:\Temp\flask_error
py -2 -m virtualenv env
.\env\Scripts\activate
pip install flask
echo $null >> hello.py

# Add content to hello.py, see below.

$env:FLASK_APP = "hello.py"
$env:FLASK_ENV = "development"
flask run

 * Serving Flask app "hello.py" (lazy loading)
 * Environment: development
 * Debug mode: on
 * Restarting with stat
c:\temp\flask_error\env\scripts\python.exe: No module named C:\Temp\flask_error\env\Scripts\flask

$env:FLASK_ENV = "production"
flask run

 * Serving Flask app "hello.py"
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

The contents of hello.py are from the flask tutorial:

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

[davidism]

I've been discussing this on Discord too, and no matter what I try, everything works for me. I'm doing the same thing everyone else is to set up an env and run it. I'm going to have a hard time fixing this if I can't observe the behavior to debug it. Someone who has the issue is going to need to debug _get_args_for_reloader() and see what values it's getting along the way and figure out where they're coming from.

[davidism]

If someone can do git bisect to find the responsible commit that would help too.

[asottile]

here's the argv / executable for that:

$ FLASK_ENV=development flask run
 * Environment: development
 * Debug mode: on
 * Restarting with stat
> c:\users\anthony\appdata\local\temp\x\venv\lib\site-packages\werkzeug\_reloader.py(68)_get_args_for_reloading()
-> rv = [sys.executable]
(Pdb) p sys.executable
'c:\\users\\anthony\\appdata\\local\\temp\\x\\venv\\scripts\\python.exe'
(Pdb) p sys.argv
['C:\\Users\\Anthony\\AppData\\Local\\Temp\\x\\venv\\Scripts\\flask', 'run']

if I use -m flask run I get this:

$ FLASK_ENV=development python -m flask run
 * Environment: development
 * Debug mode: on
 * Restarting with stat
> c:\users\anthony\appdata\local\temp\x\venv\lib\site-packages\werkzeug\_reloade
r.py(68)_get_args_for_reloading()
-> rv = [sys.executable]
(Pdb) p sys.executable
'C:\\Users\\Anthony\\AppData\\Local\\Temp\\x\\venv\\Scripts\\python.exe'
(Pdb) p sys.argv
['C:\\Users\\Anthony\\AppData\\Local\\Temp\\x\\venv\\lib\\site-packages\\flask\\
__main__.py', 'run']
(Pdb) c
 * Debugger is active!
 * Debugger PIN: 132-133-383
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

[asottile]

oops pressed enter too quickly, I have more info to post

[davidism]

It's expected that flask and -m flask will produce different args. The problem is that for flask you should be getting flask.exe, and the code around that shouldn't have changed.

[asottile]

reverting e686ae7 fixes the issue

here's where things appear to go wrong:

$ FLASK_ENV=development flask run
 * Environment: development
 * Debug mode: on
 * Restarting with stat
> c:\users\anthony\appdata\local\temp\x\werkzeug\src\werkzeug\_reloader.py(95)_get_args_for_reloading()
-> if sys.argv[0] == "-m":
(Pdb) n
> c:\users\anthony\appdata\local\temp\x\werkzeug\src\werkzeug\_reloader.py(101)_get_args_for_reloading()
-> if os.path.isfile(py_script):
(Pdb) py_script
'C:\\Users\\Anthony\\AppData\\Local\\Temp\\x\\venv\\Scripts\\flask'
(Pdb) os.path.isfile(py_script)
False
(Pdb) list
 96                 # Flask works around previous behavior by putting
 97                 # "-m flask" in sys.argv.
 98                 # TODO remove this once Flask no longer misbehaves
 99                 args = sys.argv
100             else:
101  ->             if os.path.isfile(py_script):
102                     # Rewritten by Python from "-m script" to "/path/to/script.py".
103                     py_module = __main__.__package__
104                     name = os.path.splitext(os.path.basename(py_script))[0]
105
106                     if name != "__main__":