Allow cache_timeout=0 to reach inv. cache plugins (#70977)

Change:
- Previously, `cache_timeout=0` was seen as falsey and not passed along
  to cache plugins as an option. Now only "nulley" values are not sent.

Test Plan:
- New integration tests

Tickets:
- Fixes #70702

Signed-off-by: Rick Elrod <rick@elrod.me>

lib/ansible/plugins/inventory/__init__.py

@@ -232,7 +232,7 @@ class BaseInventoryPlugin(AnsiblePlugin):
         self.set_options(direct=config)
         if 'cache' in self._options and self.get_option('cache'):
             cache_option_keys = [('_uri', 'cache_connection'), ('_timeout', 'cache_timeout'), ('_prefix', 'cache_prefix')]
-            cache_options = dict((opt[0], self.get_option(opt[1])) for opt in cache_option_keys if self.get_option(opt[1]))
+            cache_options = dict((opt[0], self.get_option(opt[1])) for opt in cache_option_keys if self.get_option(opt[1]) is not None)
             self._cache = get_cache_plugin(self.get_option('cache_plugin'), **cache_options)
 
         return config
@@ -320,7 +320,7 @@ class Cacheable(object):
     def load_cache_plugin(self):
         plugin_name = self.get_option('cache_plugin')
         cache_option_keys = [('_uri', 'cache_connection'), ('_timeout', 'cache_timeout'), ('_prefix', 'cache_prefix')]
-        cache_options = dict((opt[0], self.get_option(opt[1])) for opt in cache_option_keys if self.get_option(opt[1]))
+        cache_options = dict((opt[0], self.get_option(opt[1])) for opt in cache_option_keys if self.get_option(opt[1]) is not None)
         self._cache = get_cache_plugin(plugin_name, **cache_options)
 
     def get_cache_key(self, path):

test/integration/targets/plugin_config_for_inventory/cache_plugins/none.py

@@ -0,0 +1,62 @@
+# (c) 2014, Brian Coca, Josh Drake, et al
+# (c) 2017 Ansible Project
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+from ansible.plugins.cache import BaseCacheModule
+
+DOCUMENTATION = '''
+    cache: none
+    short_description: write-only cache (no cache)
+    description:
+        - No caching at all
+    version_added: historical
+    author: core team (@ansible-core)
+    options:
+      _timeout:
+        default: 86400
+        description: Expiration timeout for the cache plugin data
+        env:
+          - name: ANSIBLE_CACHE_PLUGIN_TIMEOUT
+        ini:
+          - key: fact_caching_timeout
+            section: defaults
+        type: integer
+'''
+
+
+class CacheModule(BaseCacheModule):
+    def __init__(self, *args, **kwargs):
+        super(CacheModule, self).__init__(*args, **kwargs)
+        self.empty = {}
+        self._timeout = self.get_option('_timeout')
+
+    def get(self, key):
+        return self.empty.get(key)
+
+    def set(self, key, value):
+        return value
+
+    def keys(self):
+        return self.empty.keys()
+
+    def contains(self, key):
+        return key in self.empty
+
+    def delete(self, key):
+        del self.emtpy[key]
+
+    def flush(self):
+        self.empty = {}
+
+    def copy(self):
+        return self.empty.copy()
+
+    def __getstate__(self):
+        return self.copy()
+
+    def __setstate__(self, data):
+        self.empty = data

test/integration/targets/plugin_config_for_inventory/config_with_parameter.yml

@@ -1,3 +1,5 @@
 plugin: test_inventory
 departments:
   - paris
+cache: yes
+cache_timeout: 0

test/integration/targets/plugin_config_for_inventory/runme.sh

@@ -14,3 +14,9 @@ ansible-inventory --list -i ./config_without_parameter.yml --export | \
 ansible-inventory --list -i ./config_with_parameter.yml --export | \
     env python -c "import json, sys; inv = json.loads(sys.stdin.read()); \
                    assert set(inv['_meta']['hostvars']['test_host']['departments']) == set(['paris'])"
+
+export ANSIBLE_CACHE_PLUGINS=cache_plugins/
+export ANSIBLE_CACHE_PLUGIN=none
+ansible-inventory --list -i ./config_with_parameter.yml --export | \
+    env python -c "import json, sys; inv = json.loads(sys.stdin.read()); \
+                   assert inv['_meta']['hostvars']['test_host']['given_timeout'] == inv['_meta']['hostvars']['test_host']['cache_timeout']"

test/integration/targets/plugin_config_for_inventory/test_inventory.py

@@ -18,6 +18,31 @@ DOCUMENTATION = '''
                 - seine-et-marne
                 - haute-garonne
             required: False
+        cache:
+            description: cache
+            type: bool
+            default: false
+            required: False
+        cache_plugin:
+            description: cache plugin
+            type: str
+            default: none
+            required: False
+        cache_timeout:
+            description: test cache parameter
+            type: integer
+            default: 7
+            required: False
+        cache_connection:
+            description: cache connection
+            type: str
+            default: /tmp/foo
+            required: False
+        cache_prefix:
+            description: cache prefix
+            type: str
+            default: prefix_
+            required: False
 '''
 
 EXAMPLES = '''
@@ -49,3 +74,10 @@ class InventoryModule(BaseInventoryPlugin):
         self.inventory.add_group(group)
         self.inventory.add_host(group=group, host=host)
         self.inventory.set_variable(host, 'departments', departments)
+
+        # Ensure the timeout we're given gets sent to the cache plugin
+        if self.get_option('cache'):
+            given_timeout = self.get_option('cache_timeout')
+            cache_timeout = self._cache._plugin.get_option('_timeout')
+            self.inventory.set_variable(host, 'given_timeout', given_timeout)
+            self.inventory.set_variable(host, 'cache_timeout', cache_timeout)