Fix callbacks accumulation when using mixins with builders (#43100)

fixes #43097

Before this PR the behavior of mixins used together with
builders was to mask completely the callbacks defined from
the class coming later in the MRO.

Here we fix the behavior by accumulating all callbacks,
and de-duplicating them later.

1 files changed, 32 insertions, 0 deletions

diff --git a/var/spack/repos/builder.test/packages/builder-and-mixins/package.py b/var/spack/repos/builder.test/packages/builder-and-mixins/package.py
new file mode 100644
index 0000000000..2e12b0e806
--- /dev/null
+++ b/var/spack/repos/builder.test/packages/builder-and-mixins/package.py
@@ -0,0 +1,32 @@
+# Copyright 2013-2024 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+import spack.builder
+from spack.build_systems import generic
+from spack.package import *
+
+
+class BuilderAndMixins(Package):
+    """This package defines a mixin for its builder"""
+
+    homepage = "http://www.example.com"
+    url = "http://www.example.com/a-1.0.tar.gz"
+
+    version("2.0", md5="abcdef0123456789abcdef0123456789")
+    version("1.0", md5="0123456789abcdef0123456789abcdef")
+
+
+class BuilderMixin(metaclass=spack.builder.PhaseCallbacksMeta):
+    @run_before("install")
+    def before_install(self):
+        pass
+
+    @run_after("install")
+    def after_install(self):
+        pass
+
+
+class GenericBuilder(BuilderMixin, generic.GenericBuilder):
+    def install(self, pkg, spec, prefix):
+        pass