uv does not recognize __main__.py?

[seppzer0]

I have a Python project that I run directly from source. Dependencies are stored within a uv-managed .venv in the project directory.

When I attempt to launch it as I normally would with PYTHONPATH=$(pwd) python3 builder/ via my system installation, I get an error:

$ PYTHONPATH=$(pwd) uv run ./builder
error: Failed to spawn: `./builder`
  Caused by: Access is denied. (os error 5)

However, if I just add the __main__.py in my command:

$ PYTHONPATH=$(pwd) uv run ./builder/__main__.py 
usage: __main__.py [-h] [--clean] {kernel,assets,bundle} ...

A custom builder for the zero kernel.

positional arguments:
  {kernel,assets,bundle}
    kernel              build the kernel
    assets              collect assets
    bundle              build the kernel + collect assets

options:
  -h, --help            show this help message and exit
  --clean               clean the root directory

..it runs successfully.

Would this be an intended behaviour or is this a bug?

[charliermarsh]

Does uv run python ./builder work as expected?

[seppzer0]

Interestingly, it does. I don't understand the difference yet, but adding python works.

[zanieb]

In the error case, we've attempted to run a directory as though it were an executable. In the latter, you've invoked Python to run the module.

We should probably special case directories with __main__.py though (and support what you attempted to do)