gh-107963: Fix set_forkserver_preload to check the type of given list (#107965)

gh-107963: Fix set_forkserver_preload to check the type of given list

Author: corona10

Lib/multiprocessing/forkserver.py

@@ -61,7 +61,7 @@ def _stop_unlocked(self):
 
     def set_forkserver_preload(self, modules_names):
         '''Set list of module names to try to load in forkserver process.'''
-        if not all(type(mod) is str for mod in self._preload_modules):
+        if not all(type(mod) is str for mod in modules_names):
             raise TypeError('module_names must be a list of strings')
         self._preload_modules = modules_names
 

Lib/test/_test_multiprocessing.py

@@ -5369,6 +5369,14 @@ def test_context(self):
             self.assertRaises(ValueError, ctx.set_start_method, None)
             self.check_context(ctx)
 
+    def test_context_check_module_types(self):
+        try:
+            ctx = multiprocessing.get_context('forkserver')
+        except ValueError:
+            raise unittest.SkipTest('forkserver should be available')
+        with self.assertRaisesRegex(TypeError, 'module_names must be a list of strings'):
+            ctx.set_forkserver_preload([1, 2, 3])
+
     def test_set_get(self):
         multiprocessing.set_forkserver_preload(PRELOAD)
         count = 0

Misc/NEWS.d/next/Library/2023-08-15-18-20-00.gh-issue-107963.20g5BG.rst

@@ -0,0 +1,2 @@
+Fix :func:`multiprocessing.set_forkserver_preload` to check the given list
+of modules names. Patch by Dong-hee Na.