bpo-38615: Add timeout parameter for IMAP4 and IMAP4_SSL constructor (GH-17203)

imaplib.IMAP4 and imaplib.IMAP4_SSL now have an optional *timeout* parameter for their constructors. Also, the imaplib.IMAP4.open() method now has an optional *timeout* parameter with this change. The overridden methods of imaplib.IMAP4_SSL and imaplib.IMAP4_stream were applied to this change.

Author: corona10

Doc/library/imaplib.rst

@@ -30,12 +30,14 @@ Three classes are provided by the :mod:`imaplib` module, :class:`IMAP4` is the
 base class:
 
 
-.. class:: IMAP4(host='', port=IMAP4_PORT)
+.. class:: IMAP4(host='', port=IMAP4_PORT, timeout=None)
 
  This class implements the actual IMAP4 protocol. The connection is created and
  protocol version (IMAP4 or IMAP4rev1) is determined when the instance is
  initialized. If *host* is not specified, ``''`` (the local host) is used. If
- *port* is omitted, the standard IMAP4 port (143) is used.
+ *port* is omitted, the standard IMAP4 port (143) is used. The optional *timeout*
+ parameter specifies a timeout in seconds for the connection attempt.
+ If timeout is not given or is None, the global default socket timeout is used.
 
  The :class:`IMAP4` class supports the :keyword:`with` statement. When used
  like this, the IMAP4 ``LOGOUT`` command is issued automatically when the
@@ -50,6 +52,9 @@ base class:
  .. versionchanged:: 3.5
  Support for the :keyword:`with` statement was added.
 
+ .. versionchanged:: 3.9
+ The optional *timeout* parameter was added.
+
 Three exceptions are defined as attributes of the :class:`IMAP4` class:
 
 
@@ -78,7 +83,7 @@ There's also a subclass for secure connections:
 
 
 .. class:: IMAP4_SSL(host='', port=IMAP4_SSL_PORT, keyfile=None, \
- certfile=None, ssl_context=None)
+ certfile=None, ssl_context=None, timeout=None)
 
  This is a subclass derived from :class:`IMAP4` that connects over an SSL
  encrypted socket (to use this class you need a socket module that was compiled
@@ -95,8 +100,12 @@ There's also a subclass for secure connections:
  mutually exclusive with *ssl_context*, a :class:`ValueError` is raised
  if *keyfile*/*certfile* is provided along with *ssl_context*.
 
+ The optional *timeout* parameter specifies a timeout in seconds for the
+ connection attempt. If timeout is not given or is None, the global default
+ socket timeout is used.
+
  .. versionchanged:: 3.3
- *ssl_context* parameter added.
+ *ssl_context* parameter was added.
 
  .. versionchanged:: 3.4
  The class now supports hostname check with
@@ -110,6 +119,8 @@ There's also a subclass for secure connections:
  :func:`ssl.create_default_context` select the system's trusted CA
  certificates for you.
 
+ .. versionchanged:: 3.9
+ The optional *timeout* parameter was added.
 
 The second subclass allows for connections created by a child process:
 
@@ -353,16 +364,22 @@ An :class:`IMAP4` instance has the following methods:
  Send ``NOOP`` to server.
 
 
-.. method:: IMAP4.open(host, port)
+.. method:: IMAP4.open(host, port, timeout=None)
 
- Opens socket to *port* at *host*. This method is implicitly called by
- the :class:`IMAP4` constructor. The connection objects established by this
- method will be used in the :meth:`IMAP4.read`, :meth:`IMAP4.readline`,
- :meth:`IMAP4.send`, and :meth:`IMAP4.shutdown` methods. You may override
- this method.
+ Opens socket to *port* at *host*. The optional *timeout* parameter
+ specifies a timeout in seconds for the connection attempt.
+ If timeout is not given or is None, the global default socket timeout
+ is used. Also note that if the *timeout* parameter is set to be zero,
+ it will raise a :class:`ValueError` to reject creating a non-blocking socket.
+ This method is implicitly called by the :class:`IMAP4` constructor.
+ The connection objects established by this method will be used in
+ the :meth:`IMAP4.read`, :meth:`IMAP4.readline`, :meth:`IMAP4.send`,
+ and :meth:`IMAP4.shutdown` methods. You may override this method.
 
  .. audit-event:: imaplib.open self,host,port imaplib.IMAP4.open
 
+ .. versionchanged:: 3.9
+ The *timeout* parameter was added.
 
 .. method:: IMAP4.partial(message_num, message_part, start, length)
 

Doc/whatsnew/3.9.rst

@@ -167,6 +167,16 @@ When the garbage collector makes a collection in which some objects resurrect
 been executed), do not block the collection of all objects that are still
 unreachable. (Contributed by Pablo Galindo and Tim Peters in :issue:`38379`.)
 
+imaplib
+-------
+
+:class:`~imaplib.IMAP4` and :class:`~imaplib.IMAP4_SSL` now have
+an optional *timeout* parameter for their constructors.
+Also, the :meth:`~imaplib.IMAP4.open` method now has an optional *timeout* parameter
+with this change. The overridden methods of :class:`~imaplib.IMAP4_SSL` and
+:class:`~imaplib.IMAP4_stream` were applied to this change.
+(Contributed by Dong-hee Na in :issue:`38615`.)
+
 os
 --
 

Lib/imaplib.py

@@ -135,10 +135,13 @@ class IMAP4:
 
  r"""IMAP4 client class.
 
- Instantiate with: IMAP4([host[, port]])
+ Instantiate with: IMAP4([host[, port[, timeout=None]]])
 
  host - host's name (default: localhost);
  port - port number (default: standard IMAP4 port).
+ timeout - socket timeout (default: None)
+ If timeout is not given or is None,
+ the global default socket timeout is used
 
  All IMAP4rev1 commands are supported by methods of the same
  name (in lower-case).
@@ -181,7 +184,7 @@ class error(Exception): pass # Logical errors - debug required
  class abort(error): pass # Service errors - close and retry
  class readonly(abort): pass # Mailbox status changed to READ-ONLY
 
- def __init__(self, host='', port=IMAP4_PORT):
+ def __init__(self, host='', port=IMAP4_PORT, timeout=None):
  self.debug = Debug
  self.state = 'LOGOUT'
  self.literal = None # A literal argument to a command
@@ -195,7 +198,7 @@ def __init__(self, host='', port=IMAP4_PORT):
 
  # Open socket to server.
 
- self.open(host, port)
+ self.open(host, port, timeout)
 
  try:
  self._connect()
@@ -284,23 +287,28 @@ def __exit__(self, *args):
  # Overridable methods
 
 
- def _create_socket(self):
+ def _create_socket(self, timeout):
  # Default value of IMAP4.host is '', but socket.getaddrinfo()
  # (which is used by socket.create_connection()) expects None
  # as a default value for host.
+ if timeout is not None and not timeout:
+ raise ValueError('Non-blocking socket (timeout=0) is not supported')
  host = None if not self.host else self.host
  sys.audit("imaplib.open", self, self.host, self.port)
- return socket.create_connection((host, self.port))
+ address = (host, self.port)
+ if timeout is not None:
+ return socket.create_connection(address, timeout)
+ return socket.create_connection(address)
 
- def open(self, host = '', port = IMAP4_PORT):
+ def open(self, host='', port=IMAP4_PORT, timeout=None):
  """Setup connection to remote server on "host:port"
  (default: localhost:standard IMAP4 port).
  This connection will be used by the routines:
  read, readline, send, shutdown.
  """
  self.host = host
  self.port = port
- self.sock = self._create_socket()
+ self.sock = self._create_socket(timeout)
  self.file = self.sock.makefile('rb')
 
 
@@ -1261,7 +1269,7 @@ class IMAP4_SSL(IMAP4):
 
  """IMAP4 client class over SSL connection
 
- Instantiate with: IMAP4_SSL([host[, port[, keyfile[, certfile[, ssl_context]]]]])
+ Instantiate with: IMAP4_SSL([host[, port[, keyfile[, certfile[, ssl_context[, timeout=None]]]]]])
 
  host - host's name (default: localhost);
  port - port number (default: standard IMAP4 SSL port);
@@ -1271,13 +1279,15 @@ class IMAP4_SSL(IMAP4):
  and private key (default: None)
  Note: if ssl_context is provided, then parameters keyfile or
  certfile should not be set otherwise ValueError is raised.
+ timeout - socket timeout (default: None) If timeout is not given or is None,
+ the global default socket timeout is used
 
  for more documentation see the docstring of the parent class IMAP4.
  """
 
 
  def __init__(self, host='', port=IMAP4_SSL_PORT, keyfile=None,
- certfile=None, ssl_context=None):
+ certfile=None, ssl_context=None, timeout=None):
  if ssl_context is not None and keyfile is not None:
  raise ValueError("ssl_context and keyfile arguments are mutually "
  "exclusive")
@@ -1294,20 +1304,20 @@ def __init__(self, host='', port=IMAP4_SSL_PORT, keyfile=None,
  ssl_context = ssl._create_stdlib_context(certfile=certfile,
  keyfile=keyfile)
  self.ssl_context = ssl_context
- IMAP4.__init__(self, host, port)
+ IMAP4.__init__(self, host, port, timeout)
 
- def _create_socket(self):
- sock = IMAP4._create_socket(self)
+ def _create_socket(self, timeout):
+ sock = IMAP4._create_socket(self, timeout)
  return self.ssl_context.wrap_socket(sock,
  server_hostname=self.host)
 
- def open(self, host='', port=IMAP4_SSL_PORT):
+ def open(self, host='', port=IMAP4_SSL_PORT, timeout=None):
  """Setup connection to remote server on "host:port".
  (default: localhost:standard IMAP4 SSL port).
  This connection will be used by the routines:
  read, readline, send, shutdown.
  """
- IMAP4.open(self, host, port)
+ IMAP4.open(self, host, port, timeout)
 
  __all__.append("IMAP4_SSL")
 
@@ -1329,7 +1339,7 @@ def __init__(self, command):
  IMAP4.__init__(self)
 
 
- def open(self, host = None, port = None):
+ def open(self, host=None, port=None, timeout=None):
  """Setup a stream connection.
  This connection will be used by the routines:
  read, readline, send, shutdown.

Lib/test/test_imaplib.py

@@ -440,6 +440,29 @@ def test_simple_with_statement(self):
  with self.imap_class(*server.server_address):
  pass
 
+ def test_imaplib_timeout_test(self):
+ _, server = self._setup(SimpleIMAPHandler)
+ addr = server.server_address[1]
+ client = self.imap_class("localhost", addr, timeout=None)
+ self.assertEqual(client.sock.timeout, None)
+ client.shutdown()
+ client = self.imap_class("localhost", addr, timeout=support.LOOPBACK_TIMEOUT)
+ self.assertEqual(client.sock.timeout, support.LOOPBACK_TIMEOUT)
+ client.shutdown()
+ with self.assertRaises(ValueError):
+ client = self.imap_class("localhost", addr, timeout=0)
+
+ def test_imaplib_timeout_functionality_test(self):
+ class TimeoutHandler(SimpleIMAPHandler):
+ def handle(self):
+ time.sleep(1)
+ SimpleIMAPHandler.handle(self)
+
+ _, server = self._setup(TimeoutHandler)
+ addr = server.server_address[1]
+ with self.assertRaises(socket.timeout):
+ client = self.imap_class("localhost", addr, timeout=0.001)
+
  def test_with_statement(self):
  _, server = self._setup(SimpleIMAPHandler, connect=False)
  with self.imap_class(*server.server_address) as imap:

Misc/NEWS.d/next/Library/2019-11-17-17-32-35.bpo-38615.OVyaNX.rst

@@ -0,0 +1,5 @@
+:class:`~imaplib.IMAP4` and :class:`~imaplib.IMAP4_SSL` now have an 
+optional *timeout* parameter for their constructors. 
+Also, the :meth:`~imaplib.IMAP4.open` method now has an optional *timeout* parameter
+with this change. The overridden methods of :class:`~imaplib.IMAP4_SSL` and
+:class:`~imaplib.IMAP4_stream` were applied to this change. Patch by Dong-hee Na.