Added class-method protocol_handlers

Protocol handlers returns a dictionary where keys are the version and
value is the protocol handler for that version. This is the same
behaviour as in the aio part.

Author: martin-neotech

neo4j/io/__init__.py

@@ -94,6 +94,42 @@ class Bolt:
 
     PROTOCOL_VERSION = None
 
+    @classmethod
+    def protocol_handlers(cls, protocol_version=None):
+        """ Return a dictionary of available Bolt protocol handlers,
+        keyed by version tuple. If an explicit protocol version is
+        provided, the dictionary will contain either zero or one items,
+        depending on whether that version is supported. If no protocol
+        version is provided, all available versions will be returned.
+
+        :param protocol_version: tuple identifying a specific protocol
+            version (e.g. (3, 5)) or None
+        :return: dictionary of version tuple to handler class for all
+            relevant and supported protocol versions
+        :raise TypeError: if protocol version is not passed in a tuple
+        """
+
+        # Carry out subclass imports locally to avoid circular
+        # dependency issues.
+        from neo4j.io._bolt3 import Bolt3
+        from neo4j.io._bolt4x0 import Bolt4x0
+
+        handlers = {
+            Bolt3.PROTOCOL_VERSION: Bolt3,
+            Bolt4x0.PROTOCOL_VERSION: Bolt4x0
+        }
+
+        if protocol_version is None:
+            return handlers
+
+        if not isinstance(protocol_version, tuple):
+            raise TypeError("Protocol version must be specified as a tuple")
+
+        if protocol_version in handlers:
+            return {protocol_version: handlers[protocol_version]}
+
+        return {}
+
     @classmethod
     def ping(cls, address, *, timeout=None, **config):
         """ Attempt to establish a Bolt connection, returning the

tests/unit/io/test_class_bolt.py

@@ -0,0 +1,50 @@
+#!/usr/bin/env python
+# -*- encoding: utf-8 -*-
+
+# Copyright (c) 2002-2020 "Neo4j,"
+# Neo4j Sweden AB [http://neo4j.com]
+#
+# This file is part of Neo4j.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import pytest
+from neo4j.io import Bolt
+
+# python -m pytest tests/unit/io/test_class_bolt.py -s -v
+
+
+def test_class_method_protocol_handlers():
+    # python -m pytest tests/unit/io/test_class_bolt.py -s -v -k test_class_method_protocol_handlers
+    protocol_handlers = Bolt.protocol_handlers()
+    assert len(protocol_handlers) == 2
+
+
+@pytest.mark.parametrize(
+    "test_input, expected",
+    [
+        ((0, 0), 0),
+        ((4, 0), 1),
+    ]
+)
+def test_class_method_protocol_handlers_with_protocol_version(test_input, expected):
+    # python -m pytest tests/unit/io/test_class_bolt.py -s -v -k test_class_method_protocol_handlers_with_protocol_version
+    protocol_handlers = Bolt.protocol_handlers(protocol_version=test_input)
+    assert len(protocol_handlers) == expected
+
+
+def test_class_method_protocol_handlers_with_invalid_protocol_version():
+    # python -m pytest tests/unit/io/test_class_bolt.py -s -v -k test_class_method_protocol_handlers_with_invalid_protocol_version
+    with pytest.raises(TypeError):
+        Bolt.protocol_handlers(protocol_version=2)