Add fake proxy generator

As I47312f4036a0b389cd3689466ab220ba558aa39a already did for Resource,
start supporting fake Proxy class generation. This requires the user
provide a ServiceDescription implementation and will autospec the
corresponding proxy class for the API version provided (or the only API
version, if only one is supported).

Change-Id: Ibc5698ea36d30960d2a6fddef7d9c33187a5b3ca
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

openstack/test/fakes.py

@@ -22,10 +22,17 @@ valid attributes and methods for both :class:`~openstack.resource.Resource` and
 
 import inspect
 import random
+from typing import (
+    Optional,
+    Type,
+)
+from unittest import mock
 import uuid
 
 from openstack import format as _format
+from openstack import proxy
 from openstack import resource
+from openstack import service_description
 
 
 def generate_fake_resource(resource_type, **attrs):
@@ -147,3 +154,81 @@ def generate_fake_resources(resource_type, count=1, attrs=None):
         attrs = {}
     for _ in range(count):
         yield generate_fake_resource(resource_type, **attrs)
+
+
+# TODO(stephenfin): It would be helpful to generate fake resources for the
+# various proxy methods also, but doing so requires deep code introspection or
+# (better) type annotations
+def generate_fake_proxy(
+    service: Type[service_description.ServiceDescription],
+    api_version: Optional[int] = None,
+) -> proxy.Proxy:
+    """Generate a fake proxy for the given service type
+
+    Example usage:
+
+    .. code-block:: python
+
+        >>> import functools
+        >>> from openstack.compute import compute_service
+        >>> from openstack.compute.v2 import server
+        >>> from openstack.test import fakes
+        >>> # create the fake proxy
+        >>> fake_compute_proxy = fakes.generate_fake_proxy(
+        ...    compute_service.ComputeService,
+        ... )
+        >>> # configure return values for various proxy APIs
+        >>> # note that this will generate new fake resources on each invocation
+        >>> fake_compute_proxy.get_server.side_effect = functools.partial(
+        ...     fakes.generate_fake_resource,
+        ...     server.Server,
+        ... )
+        >>> fake_compute_proxy.servers.side_effect = functools.partial(
+        ...     fakes.generate_fake_resources,
+        ...     server.Server,
+        ... )
+        >>> fake_compute_proxy.servers()
+        <generator object generate_fake_resources at 0x7f92768dc040>
+        >>> fake_compute_proxy.serverssss()
+        Traceback (most recent call last):
+          File "<stdin>", line 1, in <module>
+          File "/usr/lib64/python3.11/unittest/mock.py", line 653, in __getattr__
+            raise AttributeError("Mock object has no attribute %r" % name)
+        AttributeError: Mock object has no attribute 'serverssss'. Did you mean: 'server_ips'?
+
+    :param service: The service to generate the fake proxy for.
+    :type service: :class:`~openstack.service_description.ServiceDescription`
+    :param api_version: The API version to generate the fake proxy for.
+        This should be a major version must be supported by openstacksdk, as
+        specified in the ``supported_versions`` attribute of the provided
+        ``service``. This is only required if openstacksdk supports multiple
+        API versions for the given service.
+    :type api_version: int or None
+    :raises ValueError: if the ``service`` is not a valid
+        :class:`~openstack.service_description.ServiceDescription` or if
+        ``api_version`` is not supported
+    :returns: An autospecced mock of the :class:`~openstack.proxy.Proxy`
+        implementation for the specified service type and API version
+    """
+    if not issubclass(service, service_description.ServiceDescription):
+        raise ValueError(
+            f"Service {service.__name__} is not a valid ServiceDescription"
+        )
+
+    supported_versions = service.supported_versions
+
+    if api_version is None:
+        if len(supported_versions) > 1:
+            raise ValueError(
+                f"api_version was not provided but service {service.__name__} "
+                f"provides multiple API versions"
+            )
+        else:
+            api_version = list(supported_versions)[0]
+    elif str(api_version) not in supported_versions:
+        raise ValueError(
+            f"API version {api_version} is not supported by openstacksdk. "
+            f"Supported API versions are: {', '.join(supported_versions)}"
+        )
+
+    return mock.create_autospec(supported_versions[str(api_version)])