gh-93973: Add all_errors to asyncio.create_connection (#93974)

Co-authored-by: Oleg Iarygin <[email protected]>

Author: pamelafox

Doc/library/asyncio-eventloop.rst

@@ -377,7 +377,8 @@ Opening network connections
                           local_addr=None, server_hostname=None, \
                           ssl_handshake_timeout=None, \
                           ssl_shutdown_timeout=None, \
-                          happy_eyeballs_delay=None, interleave=None)
+                          happy_eyeballs_delay=None, interleave=None, \
+                          all_errors=False)
 
    Open a streaming transport connection to a given
    address specified by *host* and *port*.
@@ -468,6 +469,14 @@ Opening network connections
      to complete before aborting the connection. ``30.0`` seconds if ``None``
      (default).
 
+   * *all_errors* determines what exceptions are raised when a connection cannot
+     be created. By default, only a single ``Exception`` is raised: the first
+     exception if there is only one or all errors have same message, or a single
+     ``OSError`` with the error messages combined. When ``all_errors`` is ``True``,
+     an ``ExceptionGroup`` will be raised containing all exceptions (even if there
+     is only one).
+
+
    .. versionchanged:: 3.5
 
       Added support for SSL/TLS in :class:`ProactorEventLoop`.
@@ -500,6 +509,9 @@ Opening network connections
 
       Added the *ssl_shutdown_timeout* parameter.
 
+   .. versionchanged:: 3.12
+      *all_errors* was added.
+
    .. seealso::
 
       The :func:`open_connection` function is a high-level alternative

Lib/asyncio/base_events.py

@@ -980,7 +980,8 @@ async def create_connection(
             local_addr=None, server_hostname=None,
             ssl_handshake_timeout=None,
             ssl_shutdown_timeout=None,
-            happy_eyeballs_delay=None, interleave=None):
+            happy_eyeballs_delay=None, interleave=None,
+            all_errors=False):
         """Connect to a TCP server.
 
         Create a streaming transport connection to a given internet host and
@@ -1069,6 +1070,8 @@ async def create_connection(
 
             if sock is None:
                 exceptions = [exc for sub in exceptions for exc in sub]
+                if all_errors:
+                    raise ExceptionGroup("create_connection failed", exceptions)
                 if len(exceptions) == 1:
                     raise exceptions[0]
                 else:

Lib/test/test_asyncio/test_base_events.py

@@ -1109,6 +1109,15 @@ def _socket(*args, **kw):
 
         self.assertEqual(str(cm.exception), 'Multiple exceptions: err1, err2')
 
+        idx = -1
+        coro = self.loop.create_connection(MyProto, 'example.com', 80, all_errors=True)
+        with self.assertRaises(ExceptionGroup) as cm:
+            self.loop.run_until_complete(coro)
+
+        self.assertIsInstance(cm.exception, ExceptionGroup)
+        for e in cm.exception.exceptions:
+            self.assertIsInstance(e, OSError)
+
     @patch_socket
     def test_create_connection_timeout(self, m_socket):
         # Ensure that the socket is closed on timeout
@@ -1228,6 +1237,14 @@ def getaddrinfo_task(*args, **kwds):
         self.assertRaises(
             OSError, self.loop.run_until_complete, coro)
 
+        coro = self.loop.create_connection(MyProto, 'example.com', 80, all_errors=True)
+        with self.assertRaises(ExceptionGroup) as cm:
+            self.loop.run_until_complete(coro)
+
+        self.assertIsInstance(cm.exception, ExceptionGroup)
+        self.assertEqual(len(cm.exception.exceptions), 1)
+        self.assertIsInstance(cm.exception.exceptions[0], OSError)
+
     def test_create_connection_multiple(self):
         async def getaddrinfo(*args, **kw):
             return [(2, 1, 6, '', ('0.0.0.1', 80)),
@@ -1245,6 +1262,15 @@ def getaddrinfo_task(*args, **kwds):
         with self.assertRaises(OSError):
             self.loop.run_until_complete(coro)
 
+        coro = self.loop.create_connection(
+            MyProto, 'example.com', 80, family=socket.AF_INET, all_errors=True)
+        with self.assertRaises(ExceptionGroup) as cm:
+            self.loop.run_until_complete(coro)
+
+        self.assertIsInstance(cm.exception, ExceptionGroup)
+        for e in cm.exception.exceptions:
+            self.assertIsInstance(e, OSError)
+
     @patch_socket
     def test_create_connection_multiple_errors_local_addr(self, m_socket):
 
@@ -1276,6 +1302,16 @@ def getaddrinfo_task(*args, **kwds):
         self.assertTrue(str(cm.exception).startswith('Multiple exceptions: '))
         self.assertTrue(m_socket.socket.return_value.close.called)
 
+        coro = self.loop.create_connection(
+            MyProto, 'example.com', 80, family=socket.AF_INET,
+            local_addr=(None, 8080), all_errors=True)
+        with self.assertRaises(ExceptionGroup) as cm:
+            self.loop.run_until_complete(coro)
+
+        self.assertIsInstance(cm.exception, ExceptionGroup)
+        for e in cm.exception.exceptions:
+            self.assertIsInstance(e, OSError)
+
     def _test_create_connection_ip_addr(self, m_socket, allow_inet_pton):
         # Test the fallback code, even if this system has inet_pton.
         if not allow_inet_pton:

Misc/NEWS.d/next/Library/2022-06-18-15-06-54.gh-issue-93973.4y6UQT.rst

@@ -0,0 +1 @@
+Add keyword argument ``all_errors`` to ``asyncio.create_connection`` so that multiple connection errors can be raised as an ``ExceptionGroup``.