Fix microsoft/ptvsd#2108:

Debug multiprocess leads to AttributeError Can't get attribute on <module '__main__

Don't import multiprocessing before running user code.

Use bytes rather than unicode for __main__.__name__ on Python 2.7.

.vscode/launch.json

@@ -5,6 +5,7 @@
     "version": "0.2.0",
     "configurations": [
         {
+            "debugAdapterPath": "${workspaceFolder}/src/debugpy/adapter",
             "name": "Launch Python file",
             "type": "python",
             "request": "launch",
@@ -14,6 +15,7 @@
             "logToFile": true,
         },
         {
+            "debugAdapterPath": "${workspaceFolder}/src/debugpy/adapter",
             "name": "Attach: connect",
             "type": "python",
             "request": "attach",
@@ -24,6 +26,7 @@
             }
         },
         {
+            "debugAdapterPath": "${workspaceFolder}/src/debugpy/adapter",
             "name": "Attach: listen",
             "type": "python",
             "request": "attach",
@@ -34,12 +37,14 @@
             }
         },
         {
+            "debugAdapterPath": "${workspaceFolder}/src/debugpy/adapter",
             "name": "Attach: PID",
             "type": "python",
             "request": "attach",
             "processId": "${command:pickProcess}"
         },
         {
+            "debugAdapterPath": "${workspaceFolder}/src/debugpy/adapter",
             "name": "Debug Tests",
             "type": "python",
             "request": "test",

src/debugpy/common/log.py

@@ -281,7 +281,6 @@ def prefixed(format_string, *args, **kwargs):
 
 
 def describe_environment(header):
-    import multiprocessing
     import sysconfig
     import site  # noqa
 
@@ -321,7 +320,6 @@ def report_paths(get_paths, label=None):
 
             prefix = " " * len(prefix)
 
-    report("CPU count: {0}\n\n", multiprocessing.cpu_count())
     report("System paths:\n")
     report_paths("sys.prefix")
     report_paths("sys.base_prefix")

src/debugpy/server/cli.py

@@ -263,7 +263,7 @@ def run_file():
     log.describe_environment("Pre-launch environment:")
     log.info("Running file {0!r}", options.target)
 
-    runpy.run_path(options.target, run_name="__main__")
+    runpy.run_path(options.target, run_name=compat.force_str("__main__"))
 
 
 def run_module():

tests/debugpy/test_multiproc.py

@@ -39,6 +39,10 @@ def code_to_debug():
         import os
         import sys
 
+        # https://github.com/microsoft/ptvsd/issues/2108
+        class Foo(object):
+            pass
+
         def parent(q, a):
             from debuggee import backchannel
 
@@ -49,6 +53,10 @@ def parent(q, a):
             p.start()
             print("child spawned")
 
+            q.put("foo?")
+            foo = a.get()
+            assert isinstance(foo, Foo), repr(foo)
+
             q.put("child_pid?")
             what, child_pid = a.get()
             assert what == "child_pid"
@@ -65,6 +73,9 @@ def parent(q, a):
 
         def child(q, a):
             print("entering child")
+            assert q.get() == "foo?"
+            a.put(Foo())
+
             assert q.get() == "child_pid?"
             a.put(("child_pid", os.getpid()))