Fix #1074: Use "startDebugging" request for subprocesses

Use the request if client advertises the "supportsStartDebuggingRequest" capability.

src/debugpy/adapter/clients.py

@@ -30,6 +30,7 @@ class Client(components.Component):
             "supportsRunInTerminalRequest": False,
             "supportsMemoryReferences": False,
             "supportsArgsCanBeInterpretedByShell": False,
+            "supportsStartDebuggingRequest": False,
         }
 
     class Expectations(components.Capabilities):
@@ -688,11 +689,10 @@ class Client(components.Component):
             self.known_subprocesses.add(conn)
             self.session.notify_changed()
 
-        for key in "processId", "listen", "preLaunchTask", "postDebugTask":
+        for key in "processId", "listen", "preLaunchTask", "postDebugTask", "request":
             body.pop(key, None)
 
         body["name"] = "Subprocess {0}".format(conn.pid)
-        body["request"] = "attach"
         body["subProcessId"] = conn.pid
 
         for key in "args", "processName", "pythonArgs":
@@ -709,7 +709,14 @@ class Client(components.Component):
                 _, port = listener.getsockname()
             body["connect"]["port"] = port
 
-        self.channel.send_event("debugpyAttach", body)
+        if self.capabilities["supportsStartDebuggingRequest"]:
+            self.channel.request("startDebugging", {
+                "request": "attach",
+                "configuration": body,
+            })
+        else:
+            body["request"] = "attach"
+            self.channel.send_event("debugpyAttach", body)
 
 
 def serve(host, port):

tests/debug/session.py

@@ -84,6 +84,18 @@ class Session(object):
 
         self.client_id = "vscode"
 
+        self.capabilities = {
+            "pathFormat": "path",
+            "clientID": self.client_id,
+            "adapterID": "test",
+            "linesStartAt1": True,
+            "columnsStartAt1": True,
+            "supportsVariableType": True,
+            "supportsRunInTerminalRequest": True,
+            "supportsArgsCanBeInterpretedByShell": True,
+            "supportsStartDebuggingRequest": False,
+        }
+
         self.debuggee = None
         """psutil.Popen instance for the debuggee process."""
 
@@ -502,6 +514,10 @@ class Session(object):
             except Exception as exc:
                 log.swallow_exception('"runInTerminal" failed:')
                 raise request.cant_handle(str(exc))
+        elif request.command == "startDebugging":
+            pid = request("configuration", dict)("subProcessId", int)
+            watchdog.register_spawn(pid, f"{self.debuggee_id}-subprocess-{pid}")
+            return {}
         else:
             raise request.isnt_valid("not supported")
 
@@ -551,19 +567,7 @@ class Session(object):
             )
         )
 
-        self.request(
-            "initialize",
-            {
-                "pathFormat": "path",
-                "clientID": self.client_id,
-                "adapterID": "test",
-                "linesStartAt1": True,
-                "columnsStartAt1": True,
-                "supportsVariableType": True,
-                "supportsRunInTerminalRequest": True,
-                "supportsArgsCanBeInterpretedByShell": True,
-            },
-        )
+        self.request("initialize", self.capabilities)
 
     def all_events(self, event, body=some.object):
         return [
@@ -783,7 +787,15 @@ class Session(object):
         return StopInfo(stopped, frames, tid, fid)
 
     def wait_for_next_subprocess(self):
-        return Session(self.wait_for_next_event("debugpyAttach"))
+        message = self.timeline.wait_for_next(timeline.Event("debugpyAttach") | timeline.Request("startDebugging"))
+        if isinstance(message, timeline.EventOccurrence):
+            config = message.body
+            assert "request" in config
+        elif isinstance(message, timeline.RequestOccurrence):
+            config = dict(message.body("configuration", dict))
+            assert "request" not in config
+            config["request"] = "attach"
+        return Session(config)
 
     def wait_for_disconnect(self):
         self.timeline.wait_until_realized(timeline.Mark("disconnect"), freeze=True)

tests/debugpy/test_multiproc.py

@@ -9,7 +9,7 @@ import sys
 
 import debugpy
 import tests
-from tests import debug, log
+from tests import debug, log, timeline
 from tests.debug import runners
 from tests.patterns import some
 
@@ -151,7 +151,8 @@ def test_multiprocessing(pyfile, target, run, start_method):
 
 
 @pytest.mark.parametrize("subProcess", [True, False, None])
-def test_subprocess(pyfile, target, run, subProcess):
+@pytest.mark.parametrize("method", ["startDebugging", "debugpyAttach", ""])
+def test_subprocess(pyfile, target, run, subProcess, method):
     @pyfile
     def child():
         import os
@@ -188,6 +189,8 @@ def test_subprocess(pyfile, target, run, subProcess):
     with debug.Session() as parent_session:
         backchannel = parent_session.open_backchannel()
 
+        if method:
+            parent_session.capabilities["supportsStartDebuggingRequest"] = (method == "startDebugging")
         parent_session.config["preLaunchTask"] = "doSomething"
         parent_session.config["postDebugTask"] = "doSomethingElse"
         if subProcess is not None:
@@ -200,9 +203,19 @@ def test_subprocess(pyfile, target, run, subProcess):
             return
 
         expected_child_config = expected_subprocess_config(parent_session)
-        child_config = parent_session.wait_for_next_event("debugpyAttach")
+        
+        if method == "startDebugging":
+            subprocess_request = parent_session.timeline.wait_for_next(timeline.Request("startDebugging"))
+            child_config = subprocess_request.arguments("configuration", dict)
+            del expected_child_config["request"]
+        else:
+            child_config = parent_session.wait_for_next_event("debugpyAttach")
+
+        child_config = dict(child_config)
         child_config.pop("isOutputRedirected", None)
         assert child_config == expected_child_config
+        child_config["request"] = "attach"
+
         parent_session.proceed()
 
         with debug.Session(child_config) as child_session: