Fix BaseFileCacheModule#keys to respect prefix (#72789)

* Fix BaseFileCacheModule#keys to respect prefix

Change:
- Previously BaseFileCacheModule#keys would return keys with the cache
  prefix. These keys are impossible to retrieve from the cache without
  removing the prefix or using the cache without a prefix.
  Now it removes the prefix from the key and only returns keys that
  share the same prefix as the cache.

Test Plan:
- New unit tests

* Add explicit BaseFileCacheModule#keys test

Test that files that do not match the cache prefix are ignored.
Test that the prefix is removed from the cache key.

changelogs/fragments/ansible-test-cache-plugin.yml

@@ -0,0 +1,3 @@
+bugfixes:
+  - Fix ``keys()`` implementation of ``BaseFileCacheModule`` to strip the prefix
+    from the key and only return keys that share the same prefix as the cache.

lib/ansible/plugins/cache/__init__.py

@@ -190,10 +190,20 @@ class BaseFileCacheModule(BaseCacheModule):
         return True
 
     def keys(self):
+        # When using a prefix we must remove it from the key name before
+        # checking the expiry and returning it to the caller. Keys that do not
+        # share the same prefix cannot be fetched from the cache.
+        prefix = self.get_option('_prefix')
+        prefix_length = len(prefix)
         keys = []
         for k in os.listdir(self._cache_dir):
-            if not (k.startswith('.') or self.has_expired(k)):
+            if k.startswith('.') or not k.startswith(prefix):
+                continue
+
+            k = k[prefix_length:]
+            if not self.has_expired(k):
                 keys.append(k)
+
         return keys
 
     def contains(self, key):

test/units/plugins/cache/test_cache.py

@@ -19,6 +19,10 @@
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
+import os
+import shutil
+import tempfile
+
 from units.compat import unittest, mock
 from ansible.errors import AnsibleError
 from ansible.plugins.cache import CachePluginAdjudicator
@@ -60,14 +64,14 @@ class TestCachePluginAdjudicator(unittest.TestCase):
         assert self.cache.get('foo') is None
 
     def test___getitem__(self):
-        with pytest.raises(KeyError) as err:
+        with pytest.raises(KeyError):
             self.cache['foo']
 
     def test_pop_with_default(self):
         assert self.cache.pop('foo', 'bar') == 'bar'
 
     def test_pop_without_default(self):
-        with pytest.raises(KeyError) as err:
+        with pytest.raises(KeyError):
             assert self.cache.pop('foo')
 
     def test_pop(self):
@@ -79,6 +83,15 @@ class TestCachePluginAdjudicator(unittest.TestCase):
         self.cache.update({'cache_key': {'key2': 'updatedvalue'}})
         assert self.cache['cache_key']['key2'] == 'updatedvalue'
 
+    def test_update_cache_if_changed(self):
+        # Changes are stored in the CachePluginAdjudicator and will be
+        # persisted to the plugin when calling update_cache_if_changed()
+        # The exception is flush which flushes the plugin immediately.
+        assert len(self.cache.keys()) == 2
+        assert len(self.cache._plugin.keys()) == 0
+        self.cache.update_cache_if_changed()
+        assert len(self.cache._plugin.keys()) == 2
+
     def test_flush(self):
         # Fake that the cache already has some data in it but the adjudicator
         # hasn't loaded it in.
@@ -87,18 +100,70 @@ class TestCachePluginAdjudicator(unittest.TestCase):
         self.cache._plugin.set('another wolf', 'another animal')
 
         # The adjudicator does't know about the new entries
-        assert len(self.cache) == 2
+        assert len(self.cache.keys()) == 2
         # But the cache itself does
-        assert len(self.cache._plugin._cache) == 3
+        assert len(self.cache._plugin.keys()) == 3
 
         # If we call flush, both the adjudicator and the cache should flush
         self.cache.flush()
-        assert len(self.cache) == 0
+        assert len(self.cache.keys()) == 0
-        assert len(self.cache._plugin._cache) == 0
+        assert len(self.cache._plugin.keys()) == 0
 
 
-class TestFactCache(unittest.TestCase):
+class TestJsonFileCache(TestCachePluginAdjudicator):
+    cache_prefix = ''
+
+    def setUp(self):
+        self.cache_dir = tempfile.mkdtemp(prefix='ansible-plugins-cache-')
+        self.cache = CachePluginAdjudicator(
+            plugin_name='jsonfile', _uri=self.cache_dir,
+            _prefix=self.cache_prefix)
+        self.cache['cache_key'] = {'key1': 'value1', 'key2': 'value2'}
+        self.cache['cache_key_2'] = {'key': 'value'}
+
+    def test_keys(self):
+        # A cache without a prefix will consider all files in the cache
+        # directory as valid cache entries.
+        self.cache._plugin._dump(
+            'no prefix', os.path.join(self.cache_dir, 'no_prefix'))
+        self.cache._plugin._dump(
+            'special cache', os.path.join(self.cache_dir, 'special_test'))
+
+        # The plugin does not know the CachePluginAdjudicator entries.
+        assert sorted(self.cache._plugin.keys()) == [
+            'no_prefix', 'special_test']
+
+        assert 'no_prefix' in self.cache
+        assert 'special_test' in self.cache
+        assert 'test' not in self.cache
+        assert self.cache['no_prefix'] == 'no prefix'
+        assert self.cache['special_test'] == 'special cache'
+
+    def tearDown(self):
+        shutil.rmtree(self.cache_dir)
+
+
+class TestJsonFileCachePrefix(TestJsonFileCache):
+    cache_prefix = 'special_'
+
+    def test_keys(self):
+        # For caches with a prefix only files that match the prefix are
+        # considered. The prefix is removed from the key name.
+        self.cache._plugin._dump(
+            'no prefix', os.path.join(self.cache_dir, 'no_prefix'))
+        self.cache._plugin._dump(
+            'special cache', os.path.join(self.cache_dir, 'special_test'))
+
+        # The plugin does not know the CachePluginAdjudicator entries.
+        assert sorted(self.cache._plugin.keys()) == ['test']
+
+        assert 'no_prefix' not in self.cache
+        assert 'special_test' not in self.cache
+        assert 'test' in self.cache
+        assert self.cache['test'] == 'special cache'
 
+
+class TestFactCache(unittest.TestCase):
     def setUp(self):
         with mock.patch('ansible.constants.CACHE_PLUGIN', 'memory'):
             self.cache = FactCache()
@@ -110,6 +175,12 @@ class TestFactCache(unittest.TestCase):
         self.assertEqual(type(a_copy), dict)
         self.assertEqual(a_copy, dict(avocado='fruit', daisy='flower'))
 
+    def test_flush(self):
+        self.cache['motorcycle'] = 'vehicle'
+        self.cache['sock'] = 'clothing'
+        self.cache.flush()
+        assert len(self.cache.keys()) == 0
+
     def test_plugin_load_failure(self):
         # See https://github.com/ansible/ansible/issues/18751
         # Note no fact_connection config set, so this will fail