Fix interaction of spec literals that propagate variants with unify:false (#40789)

* Add tests to ensure variant propagation syntax can round-trip to/from string

* Add a regression test for the bug in 35298

* Reconstruct the spec constraints in the worker process

Specs do not preserve any information on propagation of variants
when round-tripping to/from JSON (which we use to pickle), but
preserve it when round-tripping to/from strings.

Therefore, we pass a spec literal to the worker and reconstruct
the Spec objects there.

2 files changed, 38 insertions, 0 deletions

diff --git a/var/spack/repos/builtin.mock/packages/client-not-foo/package.py b/var/spack/repos/builtin.mock/packages/client-not-foo/package.py
new file mode 100644
index 0000000000..03c9374b3a
--- /dev/null
+++ b/var/spack/repos/builtin.mock/packages/client-not-foo/package.py
@@ -0,0 +1,17 @@
+# Copyright 2013-2023 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)
+
+from spack.package import *
+
+
+class ClientNotFoo(Package):
+    """This package has a variant "foo", which is False by default."""
+
+    homepage = "http://www.example.com"
+    url = "http://www.example.com/c-1.0.tar.gz"
+
+    version("1.0", md5="0123456789abcdef0123456789abcdef")
+
+    variant("foo", default=False, description="")
diff --git a/var/spack/repos/builtin.mock/packages/parent-foo/package.py b/var/spack/repos/builtin.mock/packages/parent-foo/package.py
new file mode 100644
index 0000000000..61d15231f7
--- /dev/null
+++ b/var/spack/repos/builtin.mock/packages/parent-foo/package.py
@@ -0,0 +1,21 @@
+# Copyright 2013-2023 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)
+
+from spack.package import *
+
+
+class ParentFoo(Package):
+    """This package has a variant "foo", which is True by default, and depends on another
+    package which has the same variant defaulting to False.
+    """
+
+    homepage = "http://www.example.com"
+    url = "http://www.example.com/c-1.0.tar.gz"
+
+    version("1.0", md5="0123456789abcdef0123456789abcdef")
+
+    variant("foo", default=True, description="")
+
+    depends_on("client-not-foo")