fix(server/debug): robust debugpy attach with bounded wait and tests update

server/tests/python_tests/test_debug_server.py

@@ -1,4 +1,5 @@
 import sys
+import threading
 from pathlib import Path
 
 import pytest
@@ -27,27 +28,46 @@ def test_debug_endpoint_rejects_invalid_port(monkeypatch, port):
         _debug_server._debug_endpoint()
 
 
-def test_connect_debugger_retries_until_adapter_is_ready(monkeypatch):
-    class FakeDebugpy:
-        def __init__(self):
-            self.connect_calls = 0
-            self.wait_calls = 0
+class FakeDebugpy:
+    def __init__(self, refuse=False, block_wait=False):
+        self.refuse = refuse
+        self.block_wait = block_wait
+        self.connect_calls = 0
+        self.wait_calls = 0
 
-        def connect(self, endpoint):
-            assert endpoint == ("127.0.0.1", 5678)
-            self.connect_calls += 1
-            if self.connect_calls < 3:
-                raise ConnectionRefusedError("listener is starting")
+    def connect(self, endpoint):
+        assert endpoint == ("127.0.0.1", 5678)
+        self.connect_calls += 1
+        if self.refuse:
+            raise ConnectionRefusedError("no listener")
 
-        def wait_for_client(self):
-            self.wait_calls += 1
+    def wait_for_client(self):
+        self.wait_calls += 1
+        if self.block_wait:
+            threading.Event().wait()
 
+
+def test_connect_debugger_connects_once_and_waits_for_client():
     fake_debugpy = FakeDebugpy()
-    monkeypatch.setattr(_debug_server.time, "sleep", lambda _seconds: None)
 
-    _debug_server._connect_debugger(
-        fake_debugpy, "127.0.0.1", 5678, timeout=1.0
-    )
+    _debug_server._connect_debugger(fake_debugpy, "127.0.0.1", 5678, timeout=1.0)
 
-    assert fake_debugpy.connect_calls == 3
+    assert fake_debugpy.connect_calls == 1
     assert fake_debugpy.wait_calls == 1
+
+
+def test_connect_debugger_does_not_retry_refused_connection():
+    # debugpy.connect() cannot be called a second time after a refused connection.
+    fake_debugpy = FakeDebugpy(refuse=True)
+
+    with pytest.raises(RuntimeError, match="No debugpy listener"):
+        _debug_server._connect_debugger(fake_debugpy, "127.0.0.1", 5678, timeout=1.0)
+
+    assert fake_debugpy.connect_calls == 1
+
+
+def test_connect_debugger_times_out_on_stale_adapter():
+    fake_debugpy = FakeDebugpy(block_wait=True)
+
+    with pytest.raises(RuntimeError, match="stale debugpy adapter"):
+        _debug_server._connect_debugger(fake_debugpy, "127.0.0.1", 5678, timeout=0.1)