Load artifact refs the same way we load element names

1 files changed, 49 insertions, 0 deletions

diff --git a/src/buildstream/_artifactelement.py b/src/buildstream/_artifactelement.py
index 35ef89574..cfd3c29c8 100644
--- a/src/buildstream/_artifactelement.py
+++ b/src/buildstream/_artifactelement.py
@@ -32,6 +32,9 @@ from .types import Scope
 #    ref (str): The artifact ref
 #
 class ArtifactElement(Element):
+
+    __instantiated_artifacts = {}  # A hash of ArtifactElement by ref
+
     def __init__(self, context, ref):
         _, element, key = verify_artifact_ref(ref)
 
@@ -44,6 +47,52 @@ class ArtifactElement(Element):
 
         super().__init__(context, project, meta, plugin_conf)
 
+    # _new_from_artifact_ref():
+    #
+    # Recursively instantiate a new ArtifactElement instance, and its
+    # dependencies from an artifact ref
+    #
+    # Args:
+    #    ref (String): The artifact ref
+    #    context (Context): The Context object
+    #    task (Task): A task object to report progress to
+    #
+    # Returns:
+    #    (ArtifactElement): A newly created Element instance
+    #
+    @classmethod
+    def _new_from_artifact_ref(cls, ref, context, task=None):
+
+        if ref in cls.__instantiated_artifacts:
+            return cls.__instantiated_artifacts[ref]
+
+        artifact_element = ArtifactElement(context, ref)
+        # XXX: We need to call update state as it is responsible for
+        # initialising an Element/ArtifactElement's Artifact (__artifact)
+        artifact_element._update_state()
+        cls.__instantiated_artifacts[ref] = artifact_element
+
+        for dep_ref in artifact_element.get_dependency_refs(Scope.BUILD):
+            dependency = ArtifactElement._new_from_artifact_ref(dep_ref, context, task)
+            artifact_element._add_build_dependency(dependency)
+
+        return artifact_element
+
+    # _clear_artifact_refs_cache()
+    #
+    # Clear the internal artifact refs cache
+    #
+    # When loading ArtifactElements from artifact refs, we cache already
+    # instantiated ArtifactElements in order to not have to load the same
+    # ArtifactElements twice. This clears the cache.
+    #
+    # It should be called whenever we are done loading all artifacts in order
+    # to save memory.
+    #
+    @classmethod
+    def _clear_artifact_refs_cache(cls):
+        cls.__instantiated_artifacts = {}
+
     # Override Element.get_artifact_name()
     def get_artifact_name(self, key=None):
         return self._ref