Only delete zipapps cache on the main process

test_utils.py

@@ -791,6 +791,55 @@ def test_uvx_zipapps():
     assert b"app.pyz" in output, output.decode("utf-8", "replace")
 
 
+if hasattr(os, "fork"):
+    def test_multiprocessing():
+        """
+        Test deleting the cache with a multiprocessing app.
+
+        When the app forks, the cache directory should only be cleared if the main process exits.
+        """
+        _clean_paths(root=False)
+
+        secret = "XXXXXXXXXXXXX"
+        unzip_path = (test_path / "multiprocessing_test" / "cache").absolute()
+
+        Path("test.so").touch()
+
+        mock_main = Path("mock_main.py")
+        mock_main.touch()
+        mock_main.write_text(
+            f"def main():\n"
+            f"   import os, sys, os.path\n"
+            f"   is_parent = os.fork()\n"
+            f"   print({secret!r}, file=sys.stderr if is_parent else sys.stdout)\n"
+            f"   if not is_parent: return\n"
+            f"   import time; time.sleep(1)\n"
+            f"   print(os.path.isdir({str(unzip_path)!r}))\n"
+        )
+        app_path = create_app(
+            includes="mock_main.py",
+            main="mock_main:main",
+            unzip="test.so",
+            clear_zipapps_cache=True,
+            unzip_path=str(unzip_path),
+        )
+        stdout_output, stderr_output = subprocess.Popen(
+            [sys.executable, str(app_path)],
+            stderr=subprocess.PIPE,
+            stdout=subprocess.PIPE,
+            text=True,
+        ).communicate()
+
+        assert not unzip_path.exists(), "Cache dir should be deleted"
+
+        secret += "\n"
+        # Test that the child printed the string successfully and no errors got raised
+        assert stderr_output == secret, f"unexpected stderr: {stderr_output!r}"
+        # Test that the main process prints the string sucessfully
+        # and that the cache directory still exists after the child exits
+        assert stdout_output == (secret + "True\n"), f"unexpected stdout: {stdout_output!r}"
+
+
 def main():
     """
     test all cases

zipapps/ensure_zipapps.py.template

@@ -141,7 +141,11 @@ def prepare_path():
         if clear_zipapps_cache:
             import atexit
 
+            main_pid = os.getpid()
+
             def _remove_cache_folder():
+                if main_pid != os.getpid():
+                    return  # only remove folders when the main process exits
                 rm_dir_or_file(_cache_folder_path)
                 if not any(_cache_folder_path_parent.iterdir()):
                     rm_dir_or_file(_cache_folder_path_parent)