gh-110147: test_msvcrt: run console I/O tests in new processes (#110268)

Author: aisk

Lib/test/test_msvcrt.py

@@ -1,17 +1,17 @@
 import os
+import subprocess
 import sys
 import unittest
+from textwrap import dedent
 
-from test.support import os_helper
+from test.support import os_helper, requires_resource
 from test.support.os_helper import TESTFN, TESTFN_ASCII
 
 if sys.platform != "win32":
     raise unittest.SkipTest("windows related tests")
 
 import _winapi
-import msvcrt;
-
-from _testconsole import write_input, flush_console_input_buffer
+import msvcrt
 
 
 class TestFileOperations(unittest.TestCase):
@@ -61,34 +61,45 @@ def test_get_osfhandle(self):
 
 
 class TestConsoleIO(unittest.TestCase):
+    # CREATE_NEW_CONSOLE creates a "popup" window.
+    @requires_resource('gui')
+    def run_in_separated_process(self, code):
+        # Run test in a seprated process to avoid stdin conflicts.
+        # See: gh-110147
+        cmd = [sys.executable, '-c', code]
+        subprocess.run(cmd, check=True, capture_output=True,
+                       creationflags=subprocess.CREATE_NEW_CONSOLE)
+
     def test_kbhit(self):
-        h = msvcrt.get_osfhandle(sys.stdin.fileno())
-        flush_console_input_buffer(h)
-        self.assertEqual(msvcrt.kbhit(), 0)
+        code = dedent('''
+            import msvcrt
+            assert msvcrt.kbhit() == 0
+        ''')
+        self.run_in_separated_process(code)
 
     def test_getch(self):
         msvcrt.ungetch(b'c')
         self.assertEqual(msvcrt.getch(), b'c')
 
-    def test_getwch(self):
-        with open('CONIN$', 'rb', buffering=0) as stdin:
-            h = msvcrt.get_osfhandle(stdin.fileno())
-            flush_console_input_buffer(h)
+    def check_getwch(self, funcname):
+        code = dedent(f'''
+            import msvcrt
+            from _testconsole import write_input
+            with open("CONIN$", "rb", buffering=0) as stdin:
+                write_input(stdin, {ascii(c_encoded)})
+                assert msvcrt.{funcname}() == "{c}"
+        ''')
+        self.run_in_separated_process(code)
 
-            write_input(stdin, c_encoded)
-            self.assertEqual(msvcrt.getwch(), c)
+    def test_getwch(self):
+        self.check_getwch('getwch')
 
     def test_getche(self):
         msvcrt.ungetch(b'c')
         self.assertEqual(msvcrt.getche(), b'c')
 
     def test_getwche(self):
-        with open('CONIN$', 'rb', buffering=0) as stdin:
-            h = msvcrt.get_osfhandle(stdin.fileno())
-            flush_console_input_buffer(h)
-
-            write_input(stdin, c_encoded)
-            self.assertEqual(msvcrt.getwche(), c)
+        self.check_getwch('getwche')
 
     def test_putch(self):
         msvcrt.putch(b'c')

PC/_testconsole.c

@@ -133,31 +133,12 @@ _testconsole_read_output_impl(PyObject *module, PyObject *file)
     Py_RETURN_NONE;
 }
 
-/*[clinic input]
-_testconsole.flush_console_input_buffer
-    handle: HANDLE
-
-Flushes the console input buffer.
-
-All input records currently in the input buffer are discarded.
-[clinic start generated code]*/
-
-static PyObject *
-_testconsole_flush_console_input_buffer_impl(PyObject *module, void *handle)
-/*[clinic end generated code: output=1f923a81331465ce input=be8203ae84a288f5]*/
-/*[clinic end generated code:]*/
-{
-    FlushConsoleInputBuffer(handle);
-
-    Py_RETURN_NONE;
-}
 
 #include "clinic\_testconsole.c.h"
 
 PyMethodDef testconsole_methods[] = {
     _TESTCONSOLE_WRITE_INPUT_METHODDEF
     _TESTCONSOLE_READ_OUTPUT_METHODDEF
-    _TESTCONSOLE_FLUSH_CONSOLE_INPUT_BUFFER_METHODDEF
     {NULL, NULL}
 };