commandport

The contract between an application and "something that runs a process", and the check that keeps it that way. Standard library only; it imports no process, file or network module, so an application's core can depend on it.

• Types (commandport.domain): CaptureSpec / RunSpec / StreamSpec, ProcessSpec, their results with an explicit RunOutcome / LaunchMethod.
• Ports (commandport.ports): CommandCapturer, CommandStreamer, CommandRunner, LineStream, BackgroundLauncher, Supervisor. A use case takes one as an argument; an entrypoint chooses the implementation.
• Fakes (commandport.testing): FakeCommandRunner, FakeLauncher, FakeSupervisors: in-memory, no patching.
• Scan (commandport.scan): fails when code reaches for subprocess / os.system / ... outside the adapters. Configure it in pyproject.toml under [tool.commandport], run python -m commandport.scan, or call commandport.scan.assert_clean() from a test.

Implementations: lifecycle-runner (run / capture / stream) and proclaunch (detached services). Install launch-runner to get all three.

Guarantees every implementation of the contract gives: it never raises (a failure is a result with an outcome), never opens a console window on Windows, decodes text as UTF-8, closes stdin unless text is supplied, and on a timeout kills the whole process tree and reports what was printed so far.