Temporarily make namespace arg optional

In order to fix the referenced bug, we need to register cli args on
the global config object. Unfortunately, that causes issues because
our consumers are re-calling the conf object in their enforcers due
to the way we used to handle cli args. Specifically, the conf call
in the consumer fails because the namespace arg from oslo.policy is
registered as required, but they don't pass it to the conf call.

Long-term we want to stop having consumers call the conf object at
all, but in the meantime we need to provide a migration path that
doesn't break them. This change registers the namespace arg as
optional on the conf object and temporarily moves the required check
to oslo.policy. This will allow us to maintain the existing behavior
for our cli tools while not breaking consumers who haven't migrated
to the new cli arg behavior.

Note that we do have unit test coverage of this behavior[0], so we
can be reasonably confident the explicit check is maintaining
compatibility.

Change-Id: I34ce1dd15c464bec319e51d3e217e26554f1a944
Closes-Bug: 1863637
Related-Bug: 1849518
0: 6e2fe38573/oslo_policy/tests/test_generator.py (L500)

oslo_policy/generator.py

@@ -31,7 +31,6 @@ GENERATOR_OPTS = [
 
 RULE_OPTS = [
     cfg.MultiStrOpt('namespace',
-                    required=True,
                     help='Option namespace(s) under "oslo.policy.policies" in '
                          'which to query for options.'),
     cfg.StrOpt('format',
@@ -42,7 +41,6 @@ RULE_OPTS = [
 
 ENFORCER_OPTS = [
     cfg.StrOpt('namespace',
-               required=True,
                help='Option namespace under "oslo.policy.enforcer" in '
                     'which to look for a policy.Enforcer.'),
 ]
@@ -334,6 +332,17 @@ def on_load_failure_callback(*args, **kwargs):
     raise
 
 
+def _check_for_namespace_opt(conf):
+    # NOTE(bnemec): This opt is required, but due to lp#1849518 we need to
+    # make it optional while our consumers migrate to the new method of
+    # parsing cli args. Making the arg itself optional and explicitly checking
+    # for it in the tools will allow us to migrate projects without breaking
+    # anything. Once everyone has migrated, we can make the arg required again
+    # and remove this check.
+    if conf.namespace is None:
+        raise cfg.RequiredOptError('namespace', 'DEFAULT')
+
+
 def generate_sample(args=None, conf=None):
     logging.basicConfig(level=logging.WARN)
     # Allow the caller to pass in a local conf object for unit testing
@@ -342,6 +351,7 @@ def generate_sample(args=None, conf=None):
     conf.register_cli_opts(GENERATOR_OPTS + RULE_OPTS)
     conf.register_opts(GENERATOR_OPTS + RULE_OPTS)
     conf(args)
+    _check_for_namespace_opt(conf)
     _generate_sample(conf.namespace, conf.output_file, conf.format)
 
 
@@ -351,6 +361,7 @@ def generate_policy(args=None):
     conf.register_cli_opts(GENERATOR_OPTS + ENFORCER_OPTS)
     conf.register_opts(GENERATOR_OPTS + ENFORCER_OPTS)
     conf(args)
+    _check_for_namespace_opt(conf)
     _generate_policy(conf.namespace, conf.output_file)
 
 
@@ -377,6 +388,7 @@ def upgrade_policy(args=None, conf=None):
     conf.register_cli_opts(GENERATOR_OPTS + RULE_OPTS + UPGRADE_OPTS)
     conf.register_opts(GENERATOR_OPTS + RULE_OPTS + UPGRADE_OPTS)
     conf(args)
+    _check_for_namespace_opt(conf)
     with open(conf.policy, 'r') as input_data:
         policies = policy.parse_file_contents(input_data.read())
     default_policies = get_policies_dict(conf.namespace)
@@ -404,4 +416,5 @@ def list_redundant(args=None):
     conf.register_cli_opts(ENFORCER_OPTS)
     conf.register_opts(ENFORCER_OPTS)
     conf(args)
+    _check_for_namespace_opt(conf)
     _list_redundant(conf.namespace)