bpo-32662: Implement Server.start_serving() and Server.serve_forever() (#5312)

* bpo-32662: Implement Server.start_serving() and Server.serve_forever()

New methods:

* Server.start_serving(),
* Server.serve_forever(), and
* Server.is_serving().

Add 'start_serving' keyword parameter to loop.create_server() and
loop.create_unix_server().

Lib/test/test_asyncio/test_server.py

@@ -0,0 +1,117 @@
+import asyncio
+import socket
+import threading
+import unittest
+
+from test.test_asyncio import utils as test_utils
+from test.test_asyncio import functional as func_tests
+
+
+class BaseStartServer(func_tests.FunctionalTestCaseMixin):
+
+    def new_loop(self):
+        raise NotImplementedError
+
+    def test_start_server_1(self):
+        HELLO_MSG = b'1' * 1024 * 5 + b'\n'
+
+        def client(sock, addr):
+            sock.connect(addr)
+            sock.send(HELLO_MSG)
+            sock.recv_all(1)
+            sock.close()
+
+        async def serve(reader, writer):
+            await reader.readline()
+            main_task.cancel()
+            writer.write(b'1')
+            writer.close()
+            await writer.wait_closed()
+
+        async def main(srv):
+            async with srv:
+                await srv.serve_forever()
+
+        srv = self.loop.run_until_complete(asyncio.start_server(
+            serve, '127.0.0.1', 0, loop=self.loop, start_serving=False))
+
+        self.assertFalse(srv.is_serving())
+
+        main_task = self.loop.create_task(main(srv))
+
+        addr = srv.sockets[0].getsockname()
+        with self.assertRaises(asyncio.CancelledError):
+            with self.tcp_client(lambda sock: client(sock, addr)):
+                self.loop.run_until_complete(main_task)
+
+        self.assertEqual(srv.sockets, [])
+
+        self.assertIsNone(srv._sockets)
+        self.assertIsNone(srv._waiters)
+        self.assertFalse(srv.is_serving())
+
+        with self.assertRaisesRegex(RuntimeError, r'is closed'):
+            self.loop.run_until_complete(srv.serve_forever())
+
+
+class SelectorStartServerTests(BaseStartServer, unittest.TestCase):
+
+    def new_loop(self):
+        return asyncio.SelectorEventLoop()
+
+    @unittest.skipUnless(hasattr(socket, 'AF_UNIX'), 'no Unix sockets')
+    def test_start_unix_server_1(self):
+        HELLO_MSG = b'1' * 1024 * 5 + b'\n'
+        started = threading.Event()
+
+        def client(sock, addr):
+            started.wait(5)
+            sock.connect(addr)
+            sock.send(HELLO_MSG)
+            sock.recv_all(1)
+            sock.close()
+
+        async def serve(reader, writer):
+            await reader.readline()
+            main_task.cancel()
+            writer.write(b'1')
+            writer.close()
+            await writer.wait_closed()
+
+        async def main(srv):
+            async with srv:
+                self.assertFalse(srv.is_serving())
+                await srv.start_serving()
+                self.assertTrue(srv.is_serving())
+                started.set()
+                await srv.serve_forever()
+
+        with test_utils.unix_socket_path() as addr:
+            srv = self.loop.run_until_complete(asyncio.start_unix_server(
+                serve, addr, loop=self.loop, start_serving=False))
+
+            main_task = self.loop.create_task(main(srv))
+
+            with self.assertRaises(asyncio.CancelledError):
+                with self.unix_client(lambda sock: client(sock, addr)):
+                    self.loop.run_until_complete(main_task)
+
+            self.assertEqual(srv.sockets, [])
+
+            self.assertIsNone(srv._sockets)
+            self.assertIsNone(srv._waiters)
+            self.assertFalse(srv.is_serving())
+
+            with self.assertRaisesRegex(RuntimeError, r'is closed'):
+                self.loop.run_until_complete(srv.serve_forever())
+
+
+@unittest.skipUnless(hasattr(asyncio, 'ProactorEventLoop'), 'Windows only')
+class ProactorStartServerTests(BaseStartServer, unittest.TestCase):
+
+    def new_loop(self):
+        return asyncio.ProactorEventLoop()
+
+
+if __name__ == '__main__':
+    unittest.main()