gh-122133: Rework pure Python socketpair tests to avoid use of importlib.reload. (#122493)

Co-authored-by: Gregory P. Smith <greg@krypto.org>

Lib/socket.py

@@ -592,30 +592,10 @@ if hasattr(_socket.socket, "share"):
         return socket(0, 0, 0, info)
     __all__.append("fromshare")
 
-if hasattr(_socket, "socketpair"):
-
-    def socketpair(family=None, type=SOCK_STREAM, proto=0):
-        """socketpair([family[, type[, proto]]]) -> (socket object, socket object)
-
-        Create a pair of socket objects from the sockets returned by the platform
-        socketpair() function.
-        The arguments are the same as for socket() except the default family is
-        AF_UNIX if defined on the platform; otherwise, the default is AF_INET.
-        """
-        if family is None:
-            try:
-                family = AF_UNIX
-            except NameError:
-                family = AF_INET
-        a, b = _socket.socketpair(family, type, proto)
-        a = socket(family, type, proto, a.detach())
-        b = socket(family, type, proto, b.detach())
-        return a, b
-
-else:
-
-    # Origin: https://gist.github.com/4325783, by Geert Jansen.  Public domain.
-    def socketpair(family=AF_INET, type=SOCK_STREAM, proto=0):
+# Origin: https://gist.github.com/4325783, by Geert Jansen.  Public domain.
+# This is used if _socket doesn't natively provide socketpair. It's
+# always defined so that it can be patched in for testing purposes.
+def _fallback_socketpair(family=AF_INET, type=SOCK_STREAM, proto=0):
     if family == AF_INET:
         host = _LOCALHOST
     elif family == AF_INET6:
@@ -668,6 +648,21 @@ else:
         raise
 
     return (ssock, csock)
+
+if hasattr(_socket, "socketpair"):
+    def socketpair(family=None, type=SOCK_STREAM, proto=0):
+        if family is None:
+            try:
+                family = AF_UNIX
+            except NameError:
+                family = AF_INET
+        a, b = _socket.socketpair(family, type, proto)
+        a = socket(family, type, proto, a.detach())
+        b = socket(family, type, proto, b.detach())
+        return a, b
+
+else:
+    socketpair = _fallback_socketpair
     __all__.append("socketpair")
 
 socketpair.__doc__ = """socketpair([family[, type[, proto]]]) -> (socket object, socket object)

Lib/test/test_socket.py

@@ -4861,7 +4861,6 @@ class BasicSocketPairTest(SocketPairTest):
 
 
 class PurePythonSocketPairTest(SocketPairTest):
-
     # Explicitly use socketpair AF_INET or AF_INET6 to ensure that is the
     # code path we're using regardless platform is the pure python one where
     # `_socket.socketpair` does not exist.  (AF_INET does not work with
@@ -4876,28 +4875,21 @@ class PurePythonSocketPairTest(SocketPairTest):
     # Local imports in this class make for easy security fix backporting.
 
     def setUp(self):
-        import _socket
-        self._orig_sp = getattr(_socket, 'socketpair', None)
-        if self._orig_sp is not None:
+        if hasattr(_socket, "socketpair"):
+            self._orig_sp = socket.socketpair
             # This forces the version using the non-OS provided socketpair
             # emulation via an AF_INET socket in Lib/socket.py.
-            del _socket.socketpair
-            import importlib
-            global socket
-            socket = importlib.reload(socket)
+            socket.socketpair = socket._fallback_socketpair
         else:
-            pass  # This platform already uses the non-OS provided version.
+            # This platform already uses the non-OS provided version.
+            self._orig_sp = None
         super().setUp()
 
     def tearDown(self):
         super().tearDown()
-        import _socket
         if self._orig_sp is not None:
             # Restore the default socket.socketpair definition.
-            _socket.socketpair = self._orig_sp
-            import importlib
-            global socket
-            socket = importlib.reload(socket)
+            socket.socketpair = self._orig_sp
 
     def test_recv(self):
         msg = self.serv.recv(1024)