element.py: Add _can_query_cache() method

Keep the knowledge about which cache key is required for cache queries
within the Element class.

3 files changed, 13 insertions, 4 deletions

diff --git a/buildstream/_scheduler/fetchqueue.py b/buildstream/_scheduler/fetchqueue.py
index 6f4af018c..a99c3c9d7 100644
--- a/buildstream/_scheduler/fetchqueue.py
+++ b/buildstream/_scheduler/fetchqueue.py
@@ -49,8 +49,7 @@ class FetchQueue(Queue):
 
         # Optionally skip elements that are already in the artifact cache
         if self.skip_cached:
-            # cache cannot be queried until strict cache key is available
-            if element._get_strict_cache_key() is None:
+            if not element._can_query_cache():
                 return QueueStatus.WAIT
 
             if element._cached():
diff --git a/buildstream/_scheduler/pullqueue.py b/buildstream/_scheduler/pullqueue.py
index 458c65e92..3413d2783 100644
--- a/buildstream/_scheduler/pullqueue.py
+++ b/buildstream/_scheduler/pullqueue.py
@@ -39,8 +39,7 @@ class PullQueue(Queue):
         # state of dependencies may have changed, recalculate element state
         element._update_state()
 
-        # cache cannot be queried until strict cache key is available
-        if element._get_strict_cache_key() is None:
+        if not element._can_query_cache():
             return QueueStatus.WAIT
 
         if element._pull_pending():
diff --git a/buildstream/element.py b/buildstream/element.py
index c1f69947e..9bed99dc1 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -958,6 +958,17 @@ class Element(Plugin):
     def _get_strict_cache_key(self):
         return self.__strict_cache_key
 
+    # _can_query_cache():
+    #
+    # Returns whether the cache key required for cache queries is available.
+    #
+    # Returns:
+    #    (bool): True if cache can be queried
+    #
+    def _can_query_cache(self):
+        # cache cannot be queried until strict cache key is available
+        return self.__strict_cache_key is not None
+
     # _get_full_display_key():
     #
     # Returns cache keys for display purposes