commit 19e1b07da0712ec99383f679069d63eff7011bfc
author Maksim Ivanov <emaxx@chromium.org> Fri Jul 28 03:12:00 2023 +0000
committer Chromeos LUCI <chromeos-scoped@luci-project-accounts.iam.gserviceaccount.com> Fri Jul 28 19:14:23 2023 +0000
tree b5de1e4dfbc897fb151dffe610ef088beac4dae7
parent 3606d518db03446ecc03e5dcc0aee3d9ae4a339d

Fix ordering of eclass paths in Alchemy

Eclass search paths should be the inverse of the overlay's "masters"
order, to respect the intended semantics:

  "The masters list is in reverse priority order: later entries take
  precedence."

This commit fixes the divergence of the Alchemy's eclass inheritance
simulation from the real Portage's one. Note that it only makes
difference for same-named eclasses located in different places, which in
practice only means the fix is relevant for "toolchain-funcs.eclass"
(for the correct selection between its portage-stable and
chromiumos-overlay implementations).

BUG=b:293522502
TEST=add debug logging about inherited eclasses paths, build chromeos-base/chromeos-config-bsp, verify "chromiumos-overlay/eclass/toolchain-funcs.eclass" is used (and not "portage-stable/eclass/toolchain-funcs.eclass")

Change-Id: I6b33030fc1c3d66d592f51bff4c4155ecf790f47
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/bazel/+/4729041
Tested-by: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

portage/bin/alchemist/src/ebuild/ebuild_prelude.sh

diff --git a/portage/bin/alchemist/src/ebuild/ebuild_prelude.sh b/portage/bin/alchemist/src/ebuild/ebuild_prelude.sh
index 3ba11f9..2f7137c 100644
--- a/portage/bin/alchemist/src/ebuild/ebuild_prelude.sh
+++ b/portage/bin/alchemist/src/ebuild/ebuild_prelude.sh
@@ -171,15 +171,17 @@
 
 __xbuild_find_eclass() {
   local name="$1"
-  local eclass_dir path
+  local eclass_dir path result
+  # In case of multiple matches, proceed with the latest one as the eclass dirs
+  # are in the order from the least-preferred to the most-preferred ones.
   for eclass_dir in "${__xbuild_eclass_dirs[@]}"; do
     path="${eclass_dir}/${name}.eclass"
     if [[ -f "${path}" ]]; then
-      echo -n "${path}"
-      return
+      result="${path}"
     fi
   done
-  die "${name}.eclass not found"
+  [[ -z "${result}" ]] && die "${name}.eclass not found"
+  echo -n "${result}"
 }
 
 __xbuild_source_eclass() {

portage/bin/alchemist/src/repository.rs

diff --git a/portage/bin/alchemist/src/repository.rs b/portage/bin/alchemist/src/repository.rs
index e552436..b719358 100644
--- a/portage/bin/alchemist/src/repository.rs
+++ b/portage/bin/alchemist/src/repository.rs
@@ -123,6 +123,8 @@
 pub struct Repository {
     name: String,
     location: RepositoryLocation,
+    /// The list of parent repository locations (aka "masters"), in the order
+    /// from the least to the most preferred one.
     parents: Vec<RepositoryLocation>,
 }
 
@@ -158,12 +160,17 @@
         &self.location.base_dir
     }
 
+    /// Returns directories to be used for searching eclass files.
+    ///
+    /// Returned paths are sorted so that a lower-priority eclass directory
+    /// comes before a higher-priority one.
     pub fn eclass_dirs(&self) -> impl Iterator<Item = &Path> {
-        iter::once(self.location.eclass_dir.borrow()).chain(
-            self.parents
-                .iter()
-                .map(|location| location.eclass_dir.borrow()),
-        )
+        // Note the "parents" field ("masters" in the overlay layout) is already
+        // ordered in the "later entries take precedence" order.
+        self.parents
+            .iter()
+            .map(|location| location.eclass_dir.borrow())
+            .chain(iter::once(self.location.eclass_dir.borrow()))
     }
 
     pub fn profiles_dir(&self) -> &Path {