Add new condition: is-empty

Now, if operators want to check some attribute isn't specified,
they should use 'eq' condition with None, '', etc values:

    {'op': 'eq', 'field': 'inventory.bmc_addres', 'value': ''}

It would be useful to have condition plugin witch verify this case,
'is-empty' checks that field is empty string, list, dict or None value:

    {'op': 'is-empty', 'field': 'inventory.bmc_addres'}

Change-Id: I6596a067e769530092c3db34405e0f0917d2f052

doc/source/usage.rst

@@ -69,7 +69,10 @@ A condition is represented by an object with fields:
 
 * ``matches`` - requires a full match against a given regular expression;
 
-* ``contains`` - requires a value to contain a given regular expression.
+* ``contains`` - requires a value to contain a given regular expression;
+
+* ``is-empty`` - checks that field is an empty string, list, dict or
+  None value.
 
 ``field`` a `JSON path <http://goessner.net/articles/JsonPath/>`_ to the field
 in the introspection data to use in comparison.

ironic_inspector/plugins/rules.py

@@ -67,6 +67,13 @@ class NeCondition(SimpleCondition):
     op = operator.ne
 
 
+class EmptyCondition(base.RuleConditionPlugin):
+    REQUIRED_PARAMS = set()
+
+    def check(self, node_info, field, params, **kwargs):
+        return field in ('', None, [], {})
+
+
 class NetCondition(base.RuleConditionPlugin):
     def validate(self, params, **kwargs):
         super(NetCondition, self).validate(params, **kwargs)

ironic_inspector/test/functional.py

@@ -94,7 +94,8 @@ class Base(base.NodeTest):
                 'bmc_address': self.bmc_address
             },
             'root_disk': {'name': '/dev/sda', 'model': 'Big Data Disk',
-                          'size': 1000 * units.Gi},
+                          'size': 1000 * units.Gi,
+                          'wwn': None},
         }
         self.data_old_ramdisk = {
             'cpus': 4,
@@ -308,6 +309,7 @@ class Test(Base):
                     {'field': 'local_gb', 'op': 'lt', 'value': 1000},
                     {'field': 'local_gb', 'op': 'matches', 'value': '[0-9]+'},
                     {'field': 'cpu_arch', 'op': 'contains', 'value': '[0-9]+'},
+                    {'field': 'root_disk.wwn', 'op': 'is-empty'}
                 ],
                 'actions': [
                     {'action': 'set-attribute', 'path': '/extra/foo',

ironic_inspector/test/test_plugins_rules.py

@@ -115,6 +115,26 @@ class TestNetCondition(test_base.BaseTest):
                                          {'value': '192.0.2.1/24'}))
 
 
+class TestEmptyCondition(test_base.BaseTest):
+    cond = rules_plugins.EmptyCondition()
+
+    def test_check_none(self):
+        self.assertTrue(self.cond.check(None, None, {}))
+        self.assertFalse(self.cond.check(None, 0, {}))
+
+    def test_check_empty_string(self):
+        self.assertTrue(self.cond.check(None, '', {}))
+        self.assertFalse(self.cond.check(None, '16', {}))
+
+    def test_check_empty_list(self):
+        self.assertTrue(self.cond.check(None, [], {}))
+        self.assertFalse(self.cond.check(None, ['16'], {}))
+
+    def test_check_empty_dict(self):
+        self.assertTrue(self.cond.check(None, {}, {}))
+        self.assertFalse(self.cond.check(None, {'test': '16'}, {}))
+
+
 class TestFailAction(test_base.BaseTest):
     act = rules_plugins.FailAction()
 

releasenotes/notes/empty-condition-abc707b771be6be3.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  -  Added new condition plugin "is-empty", which allows to match
+     empty string, list, dictionary or None.

setup.cfg

@@ -45,6 +45,7 @@ ironic_inspector.rules.conditions =
     in-net = ironic_inspector.plugins.rules:NetCondition
     matches = ironic_inspector.plugins.rules:MatchesCondition
     contains = ironic_inspector.plugins.rules:ContainsCondition
+    is-empty = ironic_inspector.plugins.rules:EmptyCondition
 ironic_inspector.rules.actions =
     example = ironic_inspector.plugins.example:ExampleRuleAction
     fail = ironic_inspector.plugins.rules:FailAction