Return the endpoint from listen() with the in-process adapter

[karandhaodiyal28-hash]

debugpy.listen() is documented to return the (host, port) it ends up listening on, and it does — except when you pass in_process_debug_adapter=True, where it returns None:

host, port = debugpy.listen(5678, in_process_debug_adapter=True)
# TypeError: cannot unpack non-iterable NoneType object

The out-of-process path returns client_host, client_port at the end, but the in-process branch just did a bare return. This is especially annoying when you pass port 0, because there's then no way to find out which port was actually chosen.

This returns the endpoint from the in-process branch as well, and sets listen.called so both branches behave the same way with respect to the "listen already called" guard.

I added a small regression test that stubs out _settrace and checks the return value.

Fixes #1656.

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.

[rchiodo]

🔒 Automated review in progress — @rchiodo is auto-reviewing this PR.

[rchiodo]

Issue · Please address or respond

port is still the requested input value here, so listen(0, in_process_debug_adapter=True) now returns (host, 0) rather than the OS-assigned port. This does not meet the documented endpoint contract or the PR's stated port-0 motivation. Please obtain and return pydevd's bound port, or narrow the change and its description to explicitly document this limitation.

[verified]

[rchiodo]

Warning · Non-blocking recommendation

The fixed-port, no-op _settrace test only verifies that the input endpoint is echoed back; it cannot catch the port=0 contract gap. Add coverage that establishes whether the in-process path returns the resolved bound port for port 0.

[verified]