Cookiecutter FailedHookException on new project creation

[blindcat97]

Describe the bug

When I attempt to run briefcase new (in .venv, in correct directory, following the instructions from the BeeWare tutorial to the T), I get the error cookiecutter.exceptions.FailedHookException: Hook script failed. The only file created was a log. The only way I could get the build to work was to get out of .venv and use the main Python install, and there were no issues. When I returned to .venv to run briefcase dev, it ran normally.

Steps to reproduce

1. Install briefcase in a .venv via python -m pip install briefcase
2. cd to project directory and activate .venv
3. Attempt to run briefcase new with all default values
4. See error

Expected behavior

I expected briefcase to build a new project structure and not produce errors.

Screenshots

No response

Environment

• Operating System: Windows 11
• Python version: Tested on both 3.12.6 and 3.13
• Software versions:
  • Briefcase: 0.3.26
  • Toga: 0.5.3
  • Cookiecutter: 2.6.0

Logs

briefcase.2025_12_07-14_55_03.new.log

Additional context

No response

[rmartin16]

Thank you for reporting this, @blindcat97.

I haven't been able to replicate this. Cookiecutter is ostensibly failing on executing the pre_gen_project.py script....but it doesn't seem to be failing because the script is returning 1; otherwise, I think I would expect to see the print() statement somewhere in the log.

A couple questions @blindcat97:

1. Do you see this printed in your console where this failure happens?

   ERROR: `helloworld` is not a valid Python package name!
   

2. Are you able to upload the log with this error from running this command please?

   briefcase new --log -vvv
   

[blindcat97]

1. I don't see that printed anywhere. The most useful information I see is, immediately after selecting a GUI framework, the following lines appear. Note that I used helloworld2 so as not to interfere with my tutorial package.

[helloworld2] Generating a new application 'Hello World'
Using app template: https://github.com/beeware/briefcase-template, branch v0.3.26
Using existing template (sha e16f77d8521be0db2a03e71db27a387cbed466bf, updated Sun Nov 30 18:49:06 2025)
'C:\Users\blind\Documents\' is not recognized as an internal or external command,
operable program or batch file.
Stopping generation because pre_gen_project hook script didn't exit successfully

Following this is the traceback.
2. The attached log is after running that command.

briefcase.2025_12_07-17_58_31.new.log

[rmartin16]

'C:\Users\blind\Documents\' is not recognized as an internal or external command,
operable program or batch file.

Interesting. This is suspiciously close to the comma in your file path to the project:

C:\Users\blind\Documents\,Python\Projects\BeeWare_tutorial\helloworld2

I think this may be a bug in the way that Cookiecutter is running Python in new processes.

Cookiecutter is running Python via subprocess in a shell; so, the command line gets converted to a string and sent to cmd.exe. So, I think the command isn't getting parsed correctly and the pre_gen_project.py hook run fails....without ever actually running.

This also aligns with the fact you said this works if you use a Python located elsewhere.

[rmartin16]

Yep; I can reproduce if I ensure the virtual environment has a comma in its parent file path. Need to investigate if Cookiecutter just needs to escape these values first....or if Python's subprocess module should handle this better.

[blindcat97]

I was able to build and package for Windows just fine, but the same kind of error happens when I try to build for Android.

Downloading the Android emulator...
[=======================================] 100% Unzipping... platform-tools/sqlit                                                                                                                       

'C:\Users\blind\Documents\' is not recognized as an internal or external command,                                                                                                                      
operable program or batch file.
Building... errored
                                                                                                                                                                                                       
Error while building project.

I've attached the verbose log for that as well, in case it's useful.

briefcase.2025_12_07-18_54_19.build.log