Cargo (custom) runner can't execute python scripts on windows

[jschwe]

Problem

On windows cargo fails to execute a python script that is defined as a runner for a target in .cargo/config
This happens both when using cygwin and powershell to call cargo.
Here is a minimal example: https://github.com/jschwe/cargo_windows_python_test_runner_bug_example
The error produced by cargo is: could not execute process `C:\Users\jschw\CLionProjects\python_runner\tests/runner.py C:\Users\jschw\CLionProjects\python_runner\target\debug\dep s\integration_test-27f6506d67a39760.exe` (never executed)

The script contains a shebang which obviously works fine on unix, but it should work on windows too since .py files are registered to be executed by python. Calling the process printed in the error output directly from powershell works, on cygwin it works if you adjust the path to the cygwin path style.

Steps

1. Use windows
2. git clone https://github.com/jschwe/cargo_windows_python_test_runner_bug_example.git
3. cargo test or cargo test --test integration_test

Possible Solution(s)

I don't know how cargo currently invokes the runner so I have no idea if this is a simple fix or not.

Notes
Prepending 'python3' to the runner path (e.g. runner = "python3 tests/runner.py") doesn't work (currently) either, since then the path to my script would have to be absolute.
My use case is I'm using a python script as a wrapper to run the integration tests executable in qemu and possibly parse the output.

Output of cargo version:

cargo 1.45.0-nightly (9fcb8c1 2020-05-25)

[ehuss]

Windows doesn't have native support for shebang style executables. Cargo uses the normal command execution facilities, so it is not aware of file associations or anything like that.

Why doesn't using a runner like "python3 tests/runner.py" work for you? It shouldn't need an absolute path.

[jschwe]

Ah I'm sorry, it seems I confused some things and didn't look closely enough at the error message. python tests/runner.py actually does work, I just had an issue with my path since I didn't expect python3 to only be available under the python command.