Use lru_cache directly as decorator

This was added in Python 3.8

python/nav/alertengine/base.py

@@ -163,7 +163,6 @@ def check_alerts(debug=False):
 @transaction.atomic()
 def handle_new_alerts(new_alerts):
     """Handles new alerts on the queue"""
-    memoized_check_alert = lru_cache()(check_alert_against_filtergroupcontents)
     _logger = logging.getLogger('nav.alertengine.handle_new_alerts')
     accounts = []
 
@@ -232,14 +231,13 @@ def subscription_sort_key(subscription):
                 alertsubscriptions,
                 dupemap,
                 _logger,
-                memoized_check_alert,
+                check_alert_against_filtergroupcontents,
                 permissions,
             )
             del alert
         del account
         del permissions
 
-    del memoized_check_alert
     del new_alerts
     gc.collect()
 
@@ -599,6 +597,7 @@ def alert_should_be_ignored(queued_alert, subscription, now):
     )
 
 
+@lru_cache
 def check_alert_against_filtergroupcontents(alert, filtergroupcontents, atype):
     """Checks a given alert against an array of filtergroupcontents"""
 

python/nav/metrics/lookup.py

@@ -26,7 +26,8 @@
 _reverse_handlers = []
 
 
-def _lookup(metric):
+@lru_cache(maxsize=200)
+def lookup(metric):
     """
     Looks up a NAV object from a metric path.
 
@@ -42,10 +43,6 @@ def _lookup(metric):
             return func(**match.groupdict())
 
 
-# pylint: disable=C0103
-lookup = lru_cache(maxsize=200)(_lookup)
-
-
 def reverses(pattern):
     """Decorator to map regex patterns to reverse lookup functions"""
     try:

python/nav/web/ipdevinfo/host_information.py

@@ -46,7 +46,8 @@ def reverse_lookup(addresses):
                 yield {'addr': addr, 'name': name}
 
 
-def _get_host_info(host):
+@lru_cache
+def get_host_info(host):
     """Returns a dictionary containing DNS information about the host"""
     if is_valid_ip(host, strict=True):
         addresses = list(reverse_lookup([host]))
@@ -61,6 +62,3 @@ def _get_host_info(host):
             addresses = list(reverse_lookup(addresses))
 
     return {'host': host, 'addresses': addresses}
-
-
-get_host_info = lru_cache()(_get_host_info)