TypeError when trying to run tests in parallel with spawn.

[Kevin Renskers]

After updating to Django 4.1 I can no longer run my tests in parallel. I get seemingly endless errors in my terminal.

(env) $ ./manage.py test --parallel
Found 124 test(s).
Creating test database for alias 'default'...
Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
System check identified no issues (0 silenced).
Process SpawnPoolWorker-7:
Process SpawnPoolWorker-2:
Process SpawnPoolWorker-6:
Process SpawnPoolWorker-3:
Process SpawnPoolWorker-1:
Process SpawnPoolWorker-8:
Process SpawnPoolWorker-5:
Traceback (most recent call last):
Traceback (most recent call last):
Traceback (most recent call last):
Traceback (most recent call last):
Traceback (most recent call last):
Traceback (most recent call last):
  File "/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/process.py", line 315, in _bootstrap
    self.run()
  File "/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/pool.py", line 109, in worker
    initializer(*initargs)
  File "/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/process.py", line 315, in _bootstrap
    self.run()
  File "/Users/kevin/Workspace/cn-django/env/lib/python3.10/site-packages/django/test/runner.py", line 420, in _init_worker
    process_setup(*process_setup_args)
  File "/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/pool.py", line 109, in worker
    initializer(*initargs)
  File "/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/process.py", line 315, in _bootstrap
    self.run()
  File "/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/lib/python3.10/multiprocessing/process.py", line 315, in _bootstrap
    self.run()
  File "/Users/kevin/Workspace/cn-django/env/lib/python3.10/site-packages/django/test/runner.py", line 420, in _init_worker
    process_setup(*process_setup_args)
Traceback (most recent call last):
TypeError: ParallelTestSuite.process_setup() missing 1 required positional argument: 'self'

That traceback and error then keeps repeating.

If I run the tests just with ./manage.py test, everything works fine.

[Mariusz Felisiak]

It looks that I overcomplicated 41c4cb253c137edf5a96b7408ea55d57d6e0602a, sorry. Does the following patch work for you?

django/test/runner.py

@@ -443 +443 @@
     return subsuite_index, result.events
 
 
+def _process_setup_stub(*args):
+    """Stub method to simplify run() implementation."""
+    pass
+
+
 class ParallelTestSuite(unittest.TestSuite):
     """
     Run a series of tests in parallel in several processes.
@@ -461 +466 @@
 
     # In case someone wants to modify these in a subclass.
     init_worker = _init_worker
+    process_setup = _process_setup_stub
     process_setup_args = ()
     run_subsuite = _run_subsuite
     runner_class = RemoteTestRunner
@@ -474 +480 @@
         self.serialized_contents = None
         super().__init__()
 
-    def process_setup(self, *args):
-        """
-        Stub method to simplify run() implementation. "self" is never actually
-        passed because a function implementing this method (__func__) is
-        always used, not the method itself.
-        """
-        pass
-
     def run(self, result):
         """
         Distribute test cases across workers.

[Mariusz Felisiak]

​PR

[GitHub <noreply@…>]

In d4db417c:

Fixed #33891 -- Fixed test command crash when running in parallel using spawn.

Thanks Kevin Renskers for the report.

Regression in 41c4cb253c137edf5a96b7408ea55d57d6e0602a.

[Mariusz Felisiak <felisiak.mariusz@…>]

In ab860d4e:

[4.1.x] Fixed #33891 -- Fixed test command crash when running in parallel using spawn.

Thanks Kevin Renskers for the report.

Regression in 41c4cb253c137edf5a96b7408ea55d57d6e0602a.
Backport of d4db417c8e6935222d198925dd4c5ac1ca737909 from main