bpo-41544: Add missing parameters to dummy.DummyProcess and dummy.Pool

Lib/multiprocessing/dummy/__init__.py

@@ -17,10 +17,11 @@
 # Imports
 #
 
-import threading
+import array
 import sys
+import threading
 import weakref
-import array
+import warnings
 
 from .connection import Pipe
 from threading import Lock, RLock, Semaphore, BoundedSemaphore
@@ -33,8 +34,8 @@
 
 class DummyProcess(threading.Thread):
 
-    def __init__(self, group=None, target=None, name=None, args=(), kwargs=None):
-        threading.Thread.__init__(self, group, target, name, args, kwargs)
+    def __init__(self, group=None, target=None, name=None, args=(), kwargs=None, daemon=None):
+        threading.Thread.__init__(self, group, target, name, args, kwargs, daemon=daemon)
         self._pid = None
         self._children = weakref.WeakKeyDictionary()
         self._start_called = False
@@ -119,7 +120,10 @@ def Manager():
 def shutdown():
     pass
 
-def Pool(processes=None, initializer=None, initargs=()):
+def Pool(processes=None, initializer=None, initargs=(), maxtasksperchild=None):
+    if maxtasksperchild is not None:
+        warnings.warn("maxtasksperchild makes no sense for a ThreadPool and is ignored")
+
     from ..pool import ThreadPool
     return ThreadPool(processes, initializer, initargs)
 

Lib/test/test_multiprocessing_dummy.py

@@ -0,0 +1,29 @@
+import inspect
+import multiprocessing
+import unittest
+from multiprocessing import dummy
+
+
+class TestMultiprocessingDummy(unittest.TestCase):
+    def test_signatures(self):
+        """Check that the signatures in multiprocessing.dummy match these of multiprocessing."""
+
+        common = set(dummy.__all__) & set(multiprocessing.__all__)
+
+        # Skip Locks (these have no parameters anyway)
+        common.remove("Lock")
+        common.remove("RLock")
+
+        for name in common:
+            print(name)
+
+            dummy_obj = getattr(dummy, name)
+            multiprocessing_obj = getattr(multiprocessing, name)
+
+            dummy_sig = inspect.signature(dummy_obj)
+            multiprocessing_sig = inspect.signature(multiprocessing_obj)
+
+            assert dummy_sig == multiprocessing_sig, f"{name}: {dummy_sig} != {multiprocessing_sig}"
+
+if __name__ == '__main__':
+    unittest.main()

Misc/NEWS.d/next/Library/2021-11-07-07-58-35.bpo-41544._0dD3w.rst

@@ -0,0 +1 @@
+Add missing parameters to multiprocessing.dummy.DummyProcess and multiprocessing.dummy.Pool in order to match the API of multiprocessing.