Fix GraalPy compatibility

[steve-s]

Fixes debugpy compatibility with GraalPy, an alternative Python implementation.

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[rchiodo]

GitHub cannot anchor PR review comments to unchanged lines in the diff. Falling back to a general PR comment for src/debugpy/server/api.py:L233.

📍 src/debugpy/server/api.py:222
GraalPy falls through both branches here: _CAN_DAEMONIZE is False yet os.name == "posix" is True, so neither if nor elif os.name != "posix" executes. Because the __main__.py change means the GraalPy adapter no longer double-forks, it is a long-lived direct child just like the Windows case and needs the same treatment. As written, GraalPy will miss returncode = 0 and re-emit the bpo-38890 "child still alive" warning. Fix: key the second branch on child lifetime, not OS name — use a plain else: (i.e. not _CAN_DAEMONIZE, covering Windows AND GraalPy) that sets returncode = 0.

[rchiodo]

📍 src/debugpy/launcher/debuggee.py:62
The process_group keyword for subprocess.Popen was only added in Python 3.11. A GraalPy build targeting a pre-3.11 stdlib (e.g. GraalPy 23.x → 3.10) will raise TypeError: got an unexpected keyword argument 'process_group', which is caught and surfaced as "Couldn't spawn debuggee" — making launch fail entirely rather than degrading. Guard it, e.g. if ... graalpy and sys.version_info >= (3, 11): kwargs.update(process_group=0), or wrap in try/except TypeError.

[steve-s]

This would also require adding another branch to kill so that we use os.kill and not os.killpg for older GraalPy versions. Moreover, support for current and older GraalPy releases depends on fabioz/PyDev.Debugger#325, and unless that's merged and propagated to debugpy I think it's better to keep the changes in this file simple - it will work on GraalPy master (and some future release) for which fixes in fabioz/PyDev.Debugger#325 aren't necessary.

[rchiodo]

Solid GraalPy compatibility work overall. The main blocker is the if _CAN_DAEMONIZE / elif os.name != "posix" structure in api.py, which silently drops GraalPy through both branches. Keying the second branch on child lifetime (else:) rather than OS name fixes it.

[steve-s]

Thank you for the review! I addressed the blocker in the last commit. I will have to figure out CLA with my company.

[rchiodo]

Small, well-scoped GraalPy compatibility fix. Note: the api.py daemonize change correctly routes GraalPy into the plain else branch (same path as Windows), so it still receives returncode = 0 and the don't-terminate registration — no missed-warning regression. Looks good to merge.

[rchiodo]

Approved via Review Center.

[rchiodo]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[rchiodo]

The extra variable outside of the if statement seems like overkill. Why not just have this:

if hasattr(os, "fork") and os.fork() != 0:

[rchiodo]

Same thing here. It would be

if os.name == "posix" and hasattr(os, "fork")

Makes for fewer code changes.