smtplib: store the server name in ._host in .connect()

Original patch by gigaplastik, extended with a few more tests.

Addresses:
#70039
BPO 25852

Author: nmartensen

Lib/smtplib.py

@@ -244,7 +244,6 @@ def __init__(self, host='', port=0, local_hostname=None,
         will be used.
 
         """
-        self._host = host
         self.timeout = timeout
         self.esmtp_features = {}
         self.command_encoding = 'ascii'
@@ -335,6 +334,7 @@ def connect(self, host='localhost', port=0, source_address=None):
                     port = int(port)
                 except ValueError:
                     raise OSError("nonnumeric port")
+        self._host = host
         if not port:
             port = self.default_port
         sys.audit("smtplib.connect", self, host, port)

Lib/test/test_smtplib.py

@@ -158,6 +158,32 @@ def test_debuglevel_2(self):
                               re.MULTILINE)
         self.assertRegex(stderr.getvalue(), expected)
 
+    def test_host_port_host(self):
+        mock_socket.reply_with(b"220 Hello world")
+        # create instance without arguments
+        smtp = smtplib.SMTP(f"{HOST}:{self.port}")
+        # .connect must set ._host since it is used by .starttls
+        self.assertEqual(smtp._host, HOST)
+        smtp.close()
+
+    def test_explicit_connect(self):
+        mock_socket.reply_with(b"220 Hello world")
+        # create instance without arguments
+        smtp = smtplib.SMTP()
+        # .connect must set ._host since it is used by .starttls
+        smtp.connect(HOST, self.port)
+        self.assertEqual(smtp._host, HOST)
+        smtp.close()
+
+    def test_explicit_connect_host_port(self):
+        mock_socket.reply_with(b"220 Hello world")
+        # create instance without arguments
+        smtp = smtplib.SMTP()
+        # .connect must set ._host since it is used by .starttls
+        smtp.connect(f"{HOST}:{self.port}")
+        self.assertEqual(smtp._host, HOST)
+        smtp.close()
+
 
 class SMTPGeneralTests(GeneralTests, unittest.TestCase):
 

Lib/test/test_smtpnet.py

@@ -42,6 +42,59 @@ def test_connect_starttls(self):
             server.ehlo()
             server.quit()
 
+    def test_connect2_starttls(self):
+        support.get_attribute(smtplib, 'SMTP_SSL')
+        context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        context.check_hostname = False
+        context.verify_mode = ssl.CERT_NONE
+        with socket_helper.transient_internet(self.testServer):
+            server = smtplib.SMTP(f'{self.testServer}:{self.remotePort}')
+            try:
+                server.starttls(context=context)
+            except smtplib.SMTPException as e:
+                if e.args[0] == 'STARTTLS extension not supported by server.':
+                    unittest.skip(e.args[0])
+                else:
+                    raise
+            server.ehlo()
+            server.quit()
+
+    def test_connect3_starttls(self):
+        support.get_attribute(smtplib, 'SMTP_SSL')
+        context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        context.check_hostname = False
+        context.verify_mode = ssl.CERT_NONE
+        with socket_helper.transient_internet(self.testServer):
+            server = smtplib.SMTP()
+            server.connect(self.testServer, self.remotePort)
+            try:
+                server.starttls(context=context)
+            except smtplib.SMTPException as e:
+                if e.args[0] == 'STARTTLS extension not supported by server.':
+                    unittest.skip(e.args[0])
+                else:
+                    raise
+            server.ehlo()
+            server.quit()
+
+    def test_connect4_starttls(self):
+        support.get_attribute(smtplib, 'SMTP_SSL')
+        context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        context.check_hostname = False
+        context.verify_mode = ssl.CERT_NONE
+        with socket_helper.transient_internet(self.testServer):
+            server = smtplib.SMTP()
+            server.connect(f'{self.testServer}:{self.remotePort}')
+            try:
+                server.starttls(context=context)
+            except smtplib.SMTPException as e:
+                if e.args[0] == 'STARTTLS extension not supported by server.':
+                    unittest.skip(e.args[0])
+                else:
+                    raise
+            server.ehlo()
+            server.quit()
+
 
 class SmtpSSLTest(unittest.TestCase):
     testServer = 'smtp.gmail.com'