Element.__init_defaults: init if no plugin_conf

Still initialize `Element.__defaults` as usual, even if a `plugin_conf`
is not specified.

As part of the work on !1101 to introduce `ArtifactElement`s, a special
case for `__init_defaults` was made, such that none of the usual
defaults would be loaded. This seems to be because it has no config and
none of the defaults are required by ArtifactElement, although they
don't seem to adversely affect it.

Instead, treat a 'None' `plugin_conf` in the same way as the existing
case of a missing file. This avoids the appearance of having
plugin-specific behaviour in the base-class, and is perhaps less
puzzling to new contributors.

1 files changed, 8 insertions, 10 deletions

diff --git a/buildstream/element.py b/buildstream/element.py
index 65b9694a7..491d8c699 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -2383,20 +2383,18 @@ class Element(Plugin):
         defaults['public'] = element_public
 
     def __init_defaults(self, plugin_conf):
-        if plugin_conf is None:
-            return
-
         # Defaults are loaded once per class and then reused
         #
         if not self.__defaults_set:
-
-            # Load the plugin's accompanying .yaml file if one was provided
             defaults = {}
-            try:
-                defaults = _yaml.load(plugin_conf, os.path.basename(plugin_conf))
-            except LoadError as e:
-                if e.reason != LoadErrorReason.MISSING_FILE:
-                    raise e
+
+            if plugin_conf is not None:
+                # Load the plugin's accompanying .yaml file if one was provided
+                try:
+                    defaults = _yaml.load(plugin_conf, os.path.basename(plugin_conf))
+                except LoadError as e:
+                    if e.reason != LoadErrorReason.MISSING_FILE:
+                        raise e
 
             # Special case; compose any element-wide split-rules declarations
             self.__compose_default_splits(defaults)