Scope Variables In Unittest Template

Isolates the global variables in the unittest template into a function,
to prevent them from being imported.

Signed-off-by: Hassan Abouelela <hassan@hassanamr.com>

Author: HassanAbouelela

resources/unittest_template.py

@@ -2,15 +2,16 @@
 """This template is used inside snekbox to evaluate and test user code."""
 import ast
 import base64
+import functools
 import io
-import os
 import sys
 import traceback
+import typing
 import unittest
 from itertools import chain
 from types import ModuleType, SimpleNamespace
 from typing import NoReturn
-from unittest import mock
+
 
 ### USER CODE
 
@@ -20,9 +21,10 @@ class RunnerTestCase(unittest.IsolatedAsyncioTestCase):
 
 
 normal_exit = False
+_EXIT_WRAPPER_TYPE = typing.Callable[[int], None]
 
 
-def _exit_sandbox(code: int) -> NoReturn:
+def _exit_sandbox(code: int, stdout: io.StringIO, result_writer: io.StringIO) -> NoReturn:
     """
     Exit the sandbox by printing the result to the actual stdout and exit with the provided code.
 
@@ -34,64 +36,69 @@ def _exit_sandbox(code: int) -> NoReturn:
 
     137 can also be generated by NsJail when killing the process.
     """
-    print(RESULT.getvalue(), file=ORIGINAL_STDOUT, end="")
+    print(result_writer.getvalue(), file=stdout, end="")
     global normal_exit
     normal_exit = True
     sys.exit(code)
 
 
-def _load_user_module() -> ModuleType:
+def _load_user_module(result_writer, exit_wrapper: _EXIT_WRAPPER_TYPE) -> ModuleType:
     """Load the user code into a new module and return it."""
     code = base64.b64decode(USER_CODE).decode("utf8")
     try:
         ast.parse(code, "<input>")
     except SyntaxError:
-        RESULT.write("".join(traceback.format_exception(*sys.exc_info(), limit=0)))
-        _exit_sandbox(5)
+        result_writer.write("".join(traceback.format_exception(*sys.exc_info(), limit=0)))
+        exit_wrapper(5)
 
     _module = ModuleType("module")
     exec(code, _module.__dict__)
 
     return _module
 
 
-def _main() -> None:
+def _main(result_writer: io.StringIO, module: ModuleType, exit_wrapper: _EXIT_WRAPPER_TYPE) -> None:
     suite = unittest.defaultTestLoader.loadTestsFromTestCase(RunnerTestCase)
+    globals()["module"] = module
     result = suite.run(unittest.TestResult())
 
-    RESULT.write(str(int(result.wasSuccessful())))
+    result_writer.write(str(int(result.wasSuccessful())))
 
     if not result.wasSuccessful():
-        RESULT.write(
+        result_writer.write(
             ";".join(chain(
                 (error[0]._testMethodName.removeprefix("test_") for error in result.errors),
                 (failure[0]._testMethodName.removeprefix("test_") for failure in result.failures)
             ))
         )
 
-    _exit_sandbox(0)
+    exit_wrapper(0)
 
 
-try:
-    # Fake file object not writing anything
-    DEVNULL = SimpleNamespace(write=lambda *_: None, flush=lambda *_: None)
+def _entry():
+    result_writer = io.StringIO()
+    exit_wrapper = functools.partial(_exit_sandbox, stdout=sys.stdout, result_writer=result_writer)
 
-    RESULT = io.StringIO()
-    ORIGINAL_STDOUT = sys.__stdout__
+    try:
+        # Fake file object not writing anything
+        devnull = SimpleNamespace(write=lambda *_: None, flush=lambda *_: None)
 
-    # stdout/err is patched in order to control what is outputted by the runner
-    sys.__stdout__ = sys.stdout = DEVNULL
-    sys.__stderr__ = sys.stderr = DEVNULL
+        # stdout/err is patched in order to control what is outputted by the runner
+        sys.__stdout__ = sys.stdout = devnull
+        sys.__stderr__ = sys.stderr = devnull
 
-    # Load the user code as a global module variable
-    try:
-        module = _load_user_module()
+        # Load the user code as a global module variable
+        try:
+            module = _load_user_module(result_writer, exit_wrapper)
+        except BaseException as e:
+            result_writer.write(f"Uncaught exception while loading user code: {e}")
+            exit_wrapper(6)
+
+        _main(result_writer, module, exit_wrapper)
     except BaseException as e:
-        RESULT.write(f"Uncaught exception while loading user code: {e}")
-        _exit_sandbox(6)
-    _main()
-except BaseException as e:
-    if isinstance(e, SystemExit) and normal_exit:
-        raise e from None
-    RESULT.write(f"Uncaught exception inside runner: {e}")
-    _exit_sandbox(99)
+        if isinstance(e, SystemExit) and normal_exit:
+            raise e from None
+        result_writer.write(f"Uncaught exception inside runner: {e}")
+        exit_wrapper(99)
+
+_entry()