PYTHON-2795 Improve host parsing and error messages

pymongo/mongo_client.py

@@ -650,7 +650,10 @@ class MongoClient(common.BaseObject):
         opts = common._CaseInsensitiveDictionary()
         fqdn = None
         for entity in host:
-            if "://" in entity:
+            # A hostname can only include a-z, 0-9, '-' and '.'. If we find a '/'
+            # it must be a URI,
+            # https://en.wikipedia.org/wiki/Hostname#Restrictions_on_valid_host_names
+            if "/" in entity:
                 # Determine connection timeout from kwargs.
                 timeout = keyword_opts.get("connecttimeoutms")
                 if timeout is not None:

pymongo/srv_resolver.py

@@ -14,6 +14,8 @@
 
 """Support for resolving hosts and options from mongodb+srv:// URIs."""
 
+import ipaddress
+
 try:
     from dns import resolver
     _HAVE_DNSPYTHON = True
@@ -40,6 +42,9 @@ def _resolve(*args, **kwargs):
     # dnspython 1.X
     return resolver.query(*args, **kwargs)
 
+_INVALID_HOST_MSG = (
+    "Invalid URI host: %s is not a valid hostname for 'mongodb+srv://'. "
+    "Did you mean to use 'mongodb://'?")
 
 class _SrvResolver(object):
     def __init__(self, fqdn, connect_timeout=None):
@@ -47,13 +52,19 @@ class _SrvResolver(object):
         self.__connect_timeout = connect_timeout or CONNECT_TIMEOUT
 
         # Validate the fully qualified domain name.
+        try:
+            ipaddress.ip_address(fqdn)
+            raise ConfigurationError(_INVALID_HOST_MSG % ("an IP address",))
+        except ValueError:
+            pass
+
         try:
             self.__plist = self.__fqdn.split(".")[1:]
         except Exception:
-            raise ConfigurationError("Invalid URI host: %s" % (fqdn,))
+            raise ConfigurationError(_INVALID_HOST_MSG % (fqdn,))
         self.__slen = len(self.__plist)
         if self.__slen < 2:
-            raise ConfigurationError("Invalid URI host: %s" % (fqdn,))
+            raise ConfigurationError(_INVALID_HOST_MSG % (fqdn,))
 
     def get_options(self):
         try:

test/test_client.py

@@ -166,6 +166,20 @@ class ClientUnitTest(unittest.TestCase):
         with self.assertRaises(ValueError):
             MongoClient(maxPoolSize=0)
 
+    def test_uri_detection(self):
+        self.assertRaises(
+            ConfigurationError,
+            MongoClient,
+            "/foo")
+        self.assertRaises(
+            ConfigurationError,
+            MongoClient,
+            "://")
+        self.assertRaises(
+            ConfigurationError,
+            MongoClient,
+            "foo/")
+
     def test_get_db(self):
         def make_db(base, name):
             return base[name]

test/test_dns.py

@@ -142,12 +142,20 @@ class TestParsingErrors(unittest.TestCase):
     def test_invalid_host(self):
         self.assertRaisesRegex(
             ConfigurationError,
-            "Invalid URI host: mongodb",
+            "Invalid URI host: mongodb is not",
             MongoClient, "mongodb+srv://mongodb")
         self.assertRaisesRegex(
             ConfigurationError,
-            "Invalid URI host: mongodb.com",
+            "Invalid URI host: mongodb.com is not",
             MongoClient, "mongodb+srv://mongodb.com")
+        self.assertRaisesRegex(
+            ConfigurationError,
+            "Invalid URI host: an IP address is not",
+            MongoClient, "mongodb+srv://127.0.0.1")
+        self.assertRaisesRegex(
+            ConfigurationError,
+            "Invalid URI host: an IP address is not",
+            MongoClient, "mongodb+srv://[::1]")
 
 
 if __name__ == '__main__':