source.py: Make initialisation more classy

Construction of the plugin defaults and the config construction
don't actually need access to the source instance, so make them
into classmethods ready for extraction into the loader.

Signed-off-by: Daniel Silverstone <daniel.silverstone@codethink.co.uk>

1 files changed, 9 insertions, 8 deletions

diff --git a/buildstream/source.py b/buildstream/source.py
index dd1dbd40a..fe94a15d7 100644
--- a/buildstream/source.py
+++ b/buildstream/source.py
@@ -319,7 +319,7 @@ class Source(Plugin):
 
         # Collect the composited element configuration and
         # ask the element to configure itself.
-        self.__init_defaults(meta)
+        self.__init_defaults(project, meta)
         self.__config = self.__extract_config(meta)
         self.__first_pass = meta.first_pass
 
@@ -1231,21 +1231,22 @@ class Source(Plugin):
                               reason="ensure-stage-dir-fail") from e
         return directory
 
-    def __init_defaults(self, meta):
-        if not self.__defaults_set:
-            project = self._get_project()
+    @classmethod
+    def __init_defaults(cls, project, meta):
+        if not cls.__defaults_set:
             if meta.first_pass:
                 sources = project.first_pass_config.source_overrides
             else:
                 sources = project.source_overrides
-            type(self).__defaults = _yaml.node_get(sources, Mapping, self.get_kind(), default_value={})
-            type(self).__defaults_set = True
+            cls.__defaults = _yaml.node_get(sources, Mapping, meta.kind, default_value={})
+            cls.__defaults_set = True
 
     # This will resolve the final configuration to be handed
     # off to source.configure()
     #
-    def __extract_config(self, meta):
-        config = _yaml.node_get(self.__defaults, Mapping, 'config', default_value={})
+    @classmethod
+    def __extract_config(cls, meta):
+        config = _yaml.node_get(cls.__defaults, Mapping, 'config', default_value={})
         config = _yaml.node_copy(config)
 
         _yaml.composite(config, meta.config)