element.py: remove redundant `__defaults_set`

Use the conventional `None` value to indicate that the class variable
`__defaults` is not yet initialized. This lets us remove
`__defaults_set`.

1 files changed, 2 insertions, 4 deletions

diff --git a/buildstream/element.py b/buildstream/element.py
index 5d1f0622b..9ec65edaa 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -132,8 +132,7 @@ class Element(Plugin):
     All elements derive from this class, this interface defines how
     the core will be interacting with Elements.
     """
-    __defaults = {}               # The defaults from the yaml file and project
-    __defaults_set = False        # Flag, in case there are no defaults at all
+    __defaults = None             # The defaults from the yaml file and project
     __instantiated_elements = {}  # A hash of Element by MetaElement
     __redundant_source_refs = []  # A list of (source, ref) tuples which were redundantly specified
 
@@ -2371,7 +2370,7 @@ class Element(Plugin):
     def __init_defaults(self, plugin_conf):
         # Defaults are loaded once per class and then reused
         #
-        if not self.__defaults_set:
+        if self.__defaults is None:
             defaults = {}
 
             if plugin_conf is not None:
@@ -2399,7 +2398,6 @@ class Element(Plugin):
 
             # Set the data class wide
             type(self).__defaults = defaults
-            type(self).__defaults_set = True
 
     # This will resolve the final environment to be used when
     # creating sandboxes for this element