Fix compute API version snafu

novaclient 2.27.0 introduced the API microversion discovery and client.Client
now wants an api_version argument to properly work out the correct API
version in use.  OSC needs to provide this when required.

Letting the compute client plugin do the version validity checking makes more
sense than encoding it into shell.py, so I've added a new OSC plugin interface
function check_api_version() that is called from shell.py if it exists.  If it
either does not exist or it returns False the previous version checking using
API_VERSIONS is still performed.

compute.client.check_api_version() conditionally imports the new
novaclient.api_versions module and uses it if successful.  Otherwise
check_api_version() returns False and the previous code path is resumed.

One side-effect of this is that it is now valid to use --os-compute-api-version
with any valid microversion supported by the installed python-novaclient.

Closes-Bug: #1492467
Change-Id: I4535b38a5639a03a9597bf83f6394f9bb45c2b9e

openstackclient/compute/client.py

@@ -15,6 +15,7 @@
 
 import logging
 
+from openstackclient.common import exceptions
 from openstackclient.common import utils
 
 LOG = logging.getLogger(__name__)
@@ -26,6 +27,9 @@ API_VERSIONS = {
     "2": "novaclient.client",
 }
 
+# Save the microversion if in use
+_compute_api_version = None
+
 
 def make_client(instance):
     """Returns a compute service client."""
@@ -51,6 +55,9 @@ def make_client(instance):
     # Remember interface only if it is set
     kwargs = utils.build_kwargs_dict('endpoint_type', instance._interface)
 
+    if _compute_api_version is not None:
+        kwargs.update({'api_version': _compute_api_version})
+
     client = compute_client(
         session=instance.session,
         extensions=extensions,
@@ -73,3 +80,45 @@ def build_option_parser(parser):
              DEFAULT_API_VERSION +
              ' (Env: OS_COMPUTE_API_VERSION)')
     return parser
+
+
+def check_api_version(check_version):
+    """Validate version supplied by user
+
+    Returns:
+    * True if version is OK
+    * False if the version has not been checked and the previous plugin
+      check should be performed
+    * throws an exception if the version is no good
+
+    TODO(dtroyer): make the exception thrown a version-related one
+    """
+
+    # Defer client imports until we actually need them
+    try:
+        from novaclient import api_versions
+    except ImportError:
+        # Retain previous behaviour
+        return False
+
+    import novaclient
+
+    global _compute_api_version
+
+    # Copy some logic from novaclient 2.27.0 for basic version detection
+    # NOTE(dtroyer): This is only enough to resume operations using API
+    #                version 2.0 or any valid version supplied by the user.
+    _compute_api_version = api_versions.get_api_version(check_version)
+
+    if _compute_api_version > api_versions.APIVersion("2.0"):
+        if not _compute_api_version.matches(
+            novaclient.API_MIN_VERSION,
+            novaclient.API_MAX_VERSION,
+        ):
+            raise exceptions.CommandError(
+                "versions supported by client: %s - %s" % (
+                    novaclient.API_MIN_VERSION.get_string(),
+                    novaclient.API_MAX_VERSION.get_string(),
+                ),
+            )
+    return True

openstackclient/shell.py

@@ -304,11 +304,23 @@ class OpenStackShell(app.App):
             if version_opt:
                 api = mod.API_NAME
                 self.api_version[api] = version_opt
-                if version_opt not in mod.API_VERSIONS:
-                    self.log.warning(
-                        "The %s version <%s> is not in supported versions <%s>"
-                        % (api, version_opt,
-                           ', '.join(mod.API_VERSIONS.keys())))
+
+                # Add a plugin interface to let the module validate the version
+                # requested by the user
+                skip_old_check = False
+                mod_check_api_version = getattr(mod, 'check_api_version', None)
+                if mod_check_api_version:
+                    # this throws an exception if invalid
+                    skip_old_check = mod_check_api_version(version_opt)
+
+                mod_versions = getattr(mod, 'API_VERSIONS', None)
+                if not skip_old_check and mod_versions:
+                    if version_opt not in mod_versions:
+                        self.log.warning(
+                            "%s version %s is not in supported versions %s"
+                            % (api, version_opt,
+                               ', '.join(mod.API_VERSIONS.keys())))
+
                 # Command groups deal only with major versions
                 version = '.v' + version_opt.replace('.', '_').split('_')[0]
                 cmd_group = 'openstack.' + api.replace('-', '_') + version