version sniffing fix (#392)

Version sniffin are returning the Bolt Protocol Version for Bolt
Protocol 4.0+ the older versions are still using the ServerInfo.agen
string to determine the server version.

Author: martin-neotech

neo4j/__init__.py

@@ -348,18 +348,11 @@ def supports_multi_db(self):
         :return: Returns true if the server or cluster the driver connects to supports multi-databases, otherwise false.
         :rtype: bool
         """
-        from neo4j.io._bolt4x0 import Bolt4x0
-
-        multi_database = False
         cx = self._pool.acquire(access_mode=READ_ACCESS, timeout=self._pool.workspace_config.connection_acquisition_timeout, database=self._pool.workspace_config.database)
-
-        # TODO: This logic should be inside the Bolt subclasses, because it can change depending on Bolt Protocol Version.
-        if cx.PROTOCOL_VERSION >= Bolt4x0.PROTOCOL_VERSION and cx.server_info.version_info() >= Version(4, 0, 0):
-            multi_database = True
-
+        support = cx.supports_multiple_databases
         self._pool.release(cx)
 
-        return multi_database
+        return support
 
 
 class BoltDriver(Direct, Driver):

neo4j/api.py

@@ -23,6 +23,7 @@
     parse_qs,
 )
 from.exceptions import (
+    DriverError,
     ConfigurationError,
 )
 
@@ -149,12 +150,38 @@ def __init__(self, address, protocol_version):
 
     @property
     def agent(self):
+        """The server agent string the server responded with.
+
+        :return: Server agent string
+        :rtype: string
+        """
+        # Example "Neo4j/4.0.5"
+        # Example "Neo4j/4"
         return self.metadata.get("server")
 
     def version_info(self):
+        """Return the server version if available.
+
+        :return: Server Version or None
+        :rtype: tuple
+        """
         if not self.agent:
             return None
-        _, _, value = self.agent.partition("/")
+        # Note: Confirm that the server agent string begins with "Neo4j/" and fail gracefully if not.
+        # This is intended to help prevent drivers working for non-genuine Neo4j instances.
+
+        neo4j, _, value = self.agent.partition("/")
+        try:
+            assert neo4j == "Neo4j"
+        except AssertionError:
+            raise DriverError("Server name does not start with Neo4j/")
+
+        try:
+            if self.protocol_version >= (4, 0):
+                return self.protocol_version
+        except TypeError:
+            pass
+
         value = value.replace("-", ".").split(".")
         for i, v in enumerate(value):
             try:

neo4j/io/_bolt3.py

@@ -88,6 +88,7 @@ def __init__(self, unresolved_address, sock, max_connection_lifetime, *, auth=No
         self._max_connection_lifetime = max_connection_lifetime
         self._creation_timestamp = perf_counter()
         self.supports_multiple_results = False
+        self.supports_multiple_databases = False
         self._is_reset = True
 
         # Determine the user agent

neo4j/io/_bolt4x0.py

@@ -87,6 +87,7 @@ def __init__(self, unresolved_address, sock, max_connection_lifetime, *, auth=No
         self._max_connection_lifetime = max_connection_lifetime  # self.pool_config.max_connection_lifetime
         self._creation_timestamp = perf_counter()
         self.supports_multiple_results = True
+        self.supports_multiple_databases = True
         self._is_reset = True
 
         # Determine the user agent

tests/integration/test_bolt_driver.py

@@ -31,6 +31,7 @@
     unit_of_work,
     Transaction,
     Result,
+    ServerInfo,
 )
 from neo4j.exceptions import (
     ServiceUnavailable,
@@ -39,6 +40,7 @@
     ClientError,
 )
 from neo4j._exceptions import BoltHandshakeError
+from neo4j.io._bolt3 import Bolt3
 
 # python -m pytest tests/integration/test_bolt_driver.py -s -v
 
@@ -139,21 +141,28 @@ def test_supports_multi_db(bolt_uri, auth):
 
     with driver.session() as session:
         result = session.run("RETURN 1")
-        value = result.single().value()  # Consumes the result
+        _ = result.single().value()  # Consumes the result
         summary = result.consume()
         server_info = summary.server
 
+    assert isinstance(summary, ResultSummary)
+    assert isinstance(server_info, ServerInfo)
+    assert server_info.version_info() is not None
+    assert isinstance(server_info.protocol_version, Version)
+
     result = driver.supports_multi_db()
     driver.close()
 
-    if server_info.version_info() >= Version(4, 0, 0) and server_info.protocol_version >= Version(4, 0):
-        assert result is True
-        assert summary.database == "neo4j"  # This is the default database name if not set explicitly on the Neo4j Server
-        assert summary.query_type == "r"
-    else:
+    if server_info.protocol_version == Bolt3.PROTOCOL_VERSION:
         assert result is False
         assert summary.database is None
         assert summary.query_type == "r"
+    else:
+        assert result is True
+        assert server_info.version_info() >= Version(4, 0)
+        assert server_info.protocol_version >= Version(4, 0)
+        assert summary.database == "neo4j"  # This is the default database name if not set explicitly on the Neo4j Server
+        assert summary.query_type == "r"
 
 
 def test_test_multi_db_specify_database(bolt_uri, auth):

tests/integration/test_neo4j_driver.py

@@ -27,6 +27,7 @@
     Version,
     READ_ACCESS,
     ResultSummary,
+    ServerInfo,
 )
 from neo4j.exceptions import (
     ServiceUnavailable,
@@ -39,6 +40,7 @@
 from neo4j.conf import (
     RoutingConfig,
 )
+from neo4j.io._bolt3 import Bolt3
 
 # python -m pytest tests/integration/test_neo4j_driver.py -s -v
 
@@ -72,21 +74,28 @@ def test_supports_multi_db(neo4j_uri, auth, target):
 
     with driver.session() as session:
         result = session.run("RETURN 1")
-        value = result.single().value()   # Consumes the result
+        _ = result.single().value()   # Consumes the result
         summary = result.consume()
         server_info = summary.server
 
+    assert isinstance(summary, ResultSummary)
+    assert isinstance(server_info, ServerInfo)
+    assert server_info.version_info() is not None
+    assert isinstance(server_info.protocol_version, Version)
+
     result = driver.supports_multi_db()
     driver.close()
 
-    if server_info.version_info() >= Version(4, 0, 0) and server_info.protocol_version >= Version(4, 0):
-        assert result is True
-        assert summary.database == "neo4j"  # This is the default database name if not set explicitly on the Neo4j Server
-        assert summary.query_type == "r"
-    else:
+    if server_info.protocol_version == Bolt3.PROTOCOL_VERSION:
         assert result is False
         assert summary.database is None
         assert summary.query_type == "r"
+    else:
+        assert result is True
+        assert server_info.version_info() >= Version(4, 0)
+        assert server_info.protocol_version >= Version(4, 0)
+        assert summary.database == "neo4j"  # This is the default database name if not set explicitly on the Neo4j Server
+        assert summary.query_type == "r"
 
 
 def test_test_multi_db_specify_database(neo4j_uri, auth, target):