_loader/loade{r,lement}.py: Do not re-collect already collected elementsdanielsilverstone-ct/iterative-loader-bits

When multiple top level elements are specified we need to keep track
of whether we have completed the iterative collection process.

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

2 files changed, 12 insertions, 4 deletions

diff --git a/src/buildstream/_loader/loadelement.py b/src/buildstream/_loader/loadelement.py
index 684c32554..24b4e7293 100644
--- a/src/buildstream/_loader/loadelement.py
+++ b/src/buildstream/_loader/loadelement.py
@@ -62,10 +62,11 @@ class LoadElement():
         #
         # Public members
         #
-        self.node = node       # The YAML node
-        self.name = filename   # The element name
-        self.full_name = None  # The element full name (with associated junction)
-        self.deps = None       # The list of Dependency objects
+        self.node = node        # The YAML node
+        self.name = filename    # The element name
+        self.full_name = None   # The element full name (with associated junction)
+        self.deps = None        # The list of Dependency objects
+        self.meta_done = False  # If the MetaElement for this LoadElement is done
         self.node_id = next(self._counter)
 
         #
diff --git a/src/buildstream/_loader/loader.py b/src/buildstream/_loader/loader.py
index 161a8cc08..e279501ff 100644
--- a/src/buildstream/_loader/loader.py
+++ b/src/buildstream/_loader/loader.py
@@ -521,6 +521,11 @@ class Loader():
             element = element_queue.pop()
             meta_element = meta_element_queue.pop()
 
+            if element.meta_done:
+                # This can happen if there are multiple top level targets
+                # in which case, we simply skip over this element.
+                continue
+
             for dep in element.dependencies:
 
                 loader = dep.element._loader
@@ -538,6 +543,8 @@ class Loader():
                 if dep.dep_type != 'build':
                     meta_element.dependencies.append(meta_dep)
 
+            element.meta_done = True
+
         return self._meta_elements[top_element.name]
 
     # _get_loader():