Fix microsoft#1706: Multiprocessing via debug adapter

.vscode/launch.json

@@ -17,10 +17,10 @@
 
         // For these, ptvsd.adapter must be started first via the above configuration.
         {
+            //"debugServer": 8765,
             "name": "Launch Python file [debugServer]",
             "type": "python",
             "request": "launch",
-            "debugServer": 8765,
             //"console": "internalConsole",
             "console": "integratedTerminal",
             //"console": "externalTerminal",
@@ -30,12 +30,21 @@
             //"ptvsdArgs": ["--log-stderr"],
         },
         {
+            //"debugServer": 8765,
             "name": "Attach [debugServer]",
             "type": "python",
             "request": "attach",
-            "debugServer": 8765,
             "host": "localhost",
             "port": 5678,
         },
+        {
+            //"debugServer": 8765,
+            "name": "Attach Child Process [debugServer]",
+            "type": "python",
+            "request": "attach",
+            "host": "localhost",
+            "port": 5678,
+            "subProcessId": 00000,
+        },
     ]
 }

src/ptvsd/_vendored/pydevd/_pydevd_bundle/pydevd_defaults.py

@@ -1,8 +1,8 @@
 '''
 This module holds the customization settings for the debugger.
 '''
-from _pydevd_bundle.pydevd_constants import QUOTED_LINE_PROTOCOL
+from _pydevd_bundle.pydevd_constants import HTTP_JSON_PROTOCOL
 
 
 class PydevdCustomization(object):
-    DEFAULT_PROTOCOL = QUOTED_LINE_PROTOCOL
+    DEFAULT_PROTOCOL = HTTP_JSON_PROTOCOL

src/ptvsd/adapter/__main__.py

@@ -19,7 +19,7 @@
 
 def main(args):
     from ptvsd.common import log, options as common_options
-    from ptvsd.adapter import session, options as adapter_options
+    from ptvsd.adapter import ide, server, session, options as adapter_options
 
     if args.log_stderr:
         log.stderr.levels |= set(log.LEVELS)
@@ -30,30 +30,31 @@ def main(args):
     log.to_file(prefix="ptvsd.adapter")
     log.describe_environment("ptvsd.adapter startup environment:")
 
-    session = session.Session()
+    if args.for_enable_attach and args.port is None:
+        log.error("--for-enable-attach requires --port")
+        sys.exit(64)
+
+    server_host, server_port = server.listen()
+    ide_host, ide_port = ide.listen(port=args.port)
+
+    if args.for_enable_attach:
+        endpoints = {
+            "ide": {"host": ide_host, "port": ide_port},
+            "server": {"host": server_host, "port": server_port}
+        }
+        log.info("Sending endpoints to stdout: {0!r}", endpoints)
+        json.dump(endpoints, sys.stdout)
+        sys.stdout.write("\n")
+        sys.stdout.flush()
+
     if args.port is None:
-        session.connect_to_ide()
-    else:
-        if args.for_enable_attach:
-            # Users may want the adapter to choose the port for them, by setting port==0.
-            # For example, the Python Data Science extension uses this mode in enable_attach.
-            # Let enable_attach know the port that users should use to connect to the adapter.
-            with session.accept_connection_from_ide((args.host, args.port)) as (adapter_host, adapter_port):
-                # This mode is used only for enable_attach. Here, we always connect to
-                # adapter from the debug server as client. Adapter needs to start a listener
-                # and provide that port to debug server.
-                with session.accept_connection_from_server() as (server_host, server_port):
-                    connection_details = {
-                        "adapter": {"host": adapter_host, "port": adapter_port},
-                        "server": {"host": server_host, "port": server_port}
-                    }
-                    log.info("Writing to stdout for enable_attach: {0!r}", connection_details)
-                    print(json.dumps(connection_details))
-                    sys.stdout.flush()
-        else:
-            with session.accept_connection_from_ide((args.host, args.port)) as (_, adapter_port):
-                pass
-    session.wait_for_completion()
+        ide.IDE("stdio")
+
+    server.wait_until_disconnected()
+    log.info("All debug servers disconnected; waiting for remaining sessions...")
+
+    session.wait_until_ended()
+    log.info("All debug sessions have ended; exiting.")
 
 
 def _parse_argv(argv):

src/ptvsd/adapter/components.py

@@ -34,19 +34,29 @@ class Component(util.Observable):
     to wait_for() a change caused by another component.
     """
 
-    def __init__(self, session, stream):
+    def __init__(self, session, stream=None, channel=None):
+        assert (stream is None) ^ (channel is None)
         super(Component, self).__init__()
 
         self.session = session
-        stream.name = str(self)
-        self.channel = messaging.JsonMessageChannel(stream, self)
-        self.is_connected = True
-
-        self.observers += [lambda *_: session.notify_changed()]
-        self.channel.start()
+        with session:
+            # Hold the session lock to prevent message handlers from running while
+            # we're still initializing the session.
+            if channel is None:
+                stream.name = str(self)
+                channel = messaging.JsonMessageChannel(stream, self)
+                channel.start()
+            else:
+                channel.name = channel.stream.name = str(self)
+                channel.handlers = self
+
+            self.channel = channel
+            self.is_connected = True
+
+            self.observers += [lambda *_: session.notify_changed()]
 
     def __str__(self):
-        return fmt("{0}-{1}", type(self).__name__, self.session.id)
+        return fmt("{0}[{1}]", type(self).__name__, self.session.id)
 
     @property
     def ide(self):