From bd28a29b858fc741ec866301976e358ab8a038c8 Mon Sep 17 00:00:00 2001
From: Christian Kellner <christian@kellner.me>
Date: Thu, 20 Jan 2022 13:28:30 +0000
Subject: [PATCH] pipeline: do not return tree from build_stages

In the previous data model the build pipelines were nested inside
the pipeline and thus we would recurse in `build_stages`. The
tree that was built was returned and potentially became the build
tree for the pipeline that invoked `build_stages`. In the new
model of a direct acyclic graph of pipelines the build tree can
be any previously built pipeline and we just get it via the store,
which now keeps track of all previously built pipelines even if
there are not committed to it. Thus there is no need to return
the trees from `build_stages` anymore.
Adjust the short code that does the short circuit check to use
`ObjectStore.contains` instead of `ObjectStore.get` since we
do not need to object anymore.
---
 osbuild/pipeline.py | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/osbuild/pipeline.py b/osbuild/pipeline.py
index 1682c41b..369b745a 100644
--- a/osbuild/pipeline.py
+++ b/osbuild/pipeline.py
@@ -287,17 +287,14 @@ class Pipeline:
         if not build_tree:
             raise AssertionError(f"build tree {self.build} not found")
 
-        # If there are no stages, just return a clean `tree`
+        # If there are no stages, just return here
         if not self.stages:
-            tree = object_store.new()
-            return results, tree
+            return results
 
         # Check if the tree that we are supposed to build does
         # already exist. If so, short-circuit here
-        tree = object_store.get(self.id)
-
-        if tree:
-            return results, tree
+        if object_store.contains(self.id):
+            return results
 
         # Not in the store yet, need to actually build it, but maybe
         # an intermediate checkpoint exists: Find the last stage that
@@ -336,7 +333,7 @@ class Pipeline:
             if not r.success:
                 cleanup(build_tree, tree)
                 results["success"] = False
-                return results, None
+                return results
 
             # The content of the tree now corresponds to the stage that
             # was build and this can can be identified via the id of it
@@ -345,7 +342,7 @@ class Pipeline:
             if stage.checkpoint:
                 object_store.commit(tree, stage.id)
 
-        return results, tree
+        return results
 
     def run(self, store, monitor, libdir, stage_timeout=None):
         results = {"success": True}
@@ -357,10 +354,10 @@ class Pipeline:
         # tree exists, we return it as well, but we do not care if it is
         # missing, since it is not a mandatory part of the result and would
         # usually be needless overhead.
-        obj = store.get(self.id)
+        have_object = store.contains(self.id)
 
-        if not obj:
-            results, obj = self.build_stages(store, monitor, libdir, stage_timeout)
+        if not have_object:
+            results = self.build_stages(store, monitor, libdir, stage_timeout)
 
             if not results["success"]:
                 return results