Disallow creating projects with an app that starts with a number

[rmartin16]

Describe the bug

It is possible to create projects with an app that starts with a number but this is not valid.

❯ briefcase new -Q app_name=1hello --no-input && cd 1hello && briefcase dev

Using override value '1hello'

[1hello] Generating a new application 'Hello World'
Using app template: https://github.com/beeware/briefcase-template, branch v0.3.21
Template branch v0.3.21 not found; falling back to development template
Using existing template (sha af397117020084a0c284c65132c0e6c1019c1b65, updated Tue Dec 31 08:20:07 2024)

[1hello] Generated new application 'Hello World'

To run your application, type:

    $ cd 1hello
    $ briefcase dev


[1hello] Installing requirements...
Requirement already satisfied: toga-gtk~=0.4.7 in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (0.4.9.dev300+g1b7609dd8)
Requirement already satisfied: pytest in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (8.3.4)
Requirement already satisfied: pycairo>=1.17.0 in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (from toga-gtk~=0.4.7) (1.27.0)
Requirement already satisfied: pygobject>=3.50.0 in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (from toga-gtk~=0.4.7) (3.50.0)
Requirement already satisfied: toga-core==0.4.9.dev300+g1b7609dd8 in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (from toga-gtk~=0.4.7) (0.4.9.dev300+g1b7609dd8)
Requirement already satisfied: travertino>=0.3.0 in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (from toga-core==0.4.9.dev300+g1b7609dd8->toga-gtk~=0.4.7) (0.3.0)
Requirement already satisfied: exceptiongroup>=1.0.0rc8 in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (from pytest) (1.2.2)
Requirement already satisfied: iniconfig in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (from pytest) (2.0.0)
Requirement already satisfied: packaging in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (from pytest) (24.2)
Requirement already satisfied: pluggy<2,>=1.5 in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (from pytest) (1.5.0)
Requirement already satisfied: tomli>=1 in /home/russell/.pyenv/versions/3.10.15/envs/briefcase-3.10/lib/python3.10/site-packages (from pytest) (2.2.1)
Installing dev requirements... done

[1hello] Starting in dev mode...
===========================================================================
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/russell/.pyenv/versions/3.10.15/lib/python3.10/runpy.py", line 220, in run_module
    mod_name, mod_spec, code = _get_module_details(mod_name)
  File "/home/russell/.pyenv/versions/3.10.15/lib/python3.10/runpy.py", line 146, in _get_module_details
    return _get_module_details(pkg_main_name, error)
  File "/home/russell/.pyenv/versions/3.10.15/lib/python3.10/runpy.py", line 157, in _get_module_details
    code = loader.get_code(mod_name)
  File "<frozen importlib._bootstrap_external>", line 1017, in get_code
  File "<frozen importlib._bootstrap_external>", line 947, in source_to_code
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/home/russell/tmp/beeware/1hello/src/1hello/__main__.py", line 1
    from 1hello.app import main
         ^
SyntaxError: invalid decimal literal

Problem running app 1hello.

Steps to reproduce

Run briefcase new -Q app_name=1hello --no-input && cd 1hello && briefcase dev

Expected behavior

App names that begin with a number should not be allowed.

Screenshots

No response

Environment

• Operating System: pop os 22.04
• Python version: 3.10
• Software versions:
  • Briefcase: 0.3.21.dev125+gdced62d4

Logs

briefcase.2025_01_21-00_06_20.dev.log

Additional context

No response

[freakboy3742]

... huh.

I'm more than a little surprised by this one, honestly. I didn't know that PEP 508 allowed specifying a module name that isn't valid Python module... I guess it makes sense, though, as there's no hard requirement that the module installed by a PyPI package matches the name of the PyPI package.

[manognya-b]

Can I take up this issue? Will send out updates on progress and blockers if any!

[freakboy3742]

@manognya-b Absolutely! We don't formally assign bugs, so feel free to submit a fix (and an update for the existing test!)

[manognya-b]

Hello again, I've disallowed app names that begin with numbers and it is working as expected and rejecting both single and multiple character strings that begin with numbers. However, I noticed a phenomenon where app names that contain a "." character are being parsed incorrectly during the briefcase dev run.

@manognya-b ➜ /workspaces/briefcase (2127.bugfix.invalid-app-name) $ briefcase new -Q app_name=hello.1 --no-input && cd hello.1 && briefcase d
ev

Using override value 'hello.1'

[hello.1] Generating a new application 'Hello World'
Using app template: https://github.com/beeware/briefcase-template, branch v0.1
Template branch v0.1 not found; falling back to development template
Using existing template (sha af397117020084a0c284c65132c0e6c1019c1b65, updated Tue Dec 31 08:20:07 2024)

[hello.1] Generated new application 'Hello World'

To run your application, type:

    $ cd hello.1
    $ briefcase dev


Briefcase configuration error: Configuration for 'hello' is incomplete (missing 'description', 'sources')

As seen above, the app name hello.1 is being truncated to hello. A temporary fix for this would be to disallow . usages in app names, but as per PEP508 compliance rules, usage of a . as long it isn't the beginning or ending of the string seems legal.

Reference: https://peps.python.org/pep-0508/#:~:text=%5E(%5BA%2DZ0%2D9%5D%7C%5BA%2DZ0%2D9%5D%5BA%2DZ0%2D9._%2D%5D*%5BA%2DZ0%2D9%5D)%24

(Something interesting: the reference regex is allowing numbers to be used at the beginning of strings?)

Would this be a separate issue as it could be related to how briefcase is parsing app names? Thanks!

[freakboy3742]

Hello again, I've disallowed app names that begin with numbers and it is working as expected and rejecting both single and multiple character strings that begin with numbers. However, I noticed a phenomenon where app names that contain a "." character are being parsed incorrectly during the briefcase dev run.

Nice catch! I can confirm that's the behaviour I'm seeing as well.

As seen above, the app name hello.1 is being truncated to hello. A temporary fix for this would be to disallow . usages in app names, but as per PEP508 compliance rules, usage of a . as long it isn't the beginning or ending of the string seems legal.

I think this is pointing at the root of the problem - PEP508 compliance is clearly the wrong rule to be applying here. There are plenty of names that are valid PyPI package names, but have no meaningful way to be used as module names.

It looks like we actually need a strict subset of PEP 508 - identifiers that are valid PEP 508, but can also be converted into a valid identifier. Thankfully, the latter can be validated using str.isdentifier() in the standard library. We also need to allow for the hello-world case (because that's a valid PEP 508 name, but is converted by Briefcase into hello_world as a module name; so validating candidate.replace('-','_').isidentifier() should be sufficient. That should completely remove then need to check PEP 508, because any identifier that satisifies that check would also be PEP 508 compliant.

(of course, we then also need to update all the places in the documentation and help strings where we say "PEP 508" is the rule for app names...)