ASP-based solver: variants set from cli are considered as defaults (#23542)

Variants explicitly set in an abstract root spec are considered
as defaults for the package they refer to, and they override
what is in packages.yaml and in package.py. This is relevant
only for multi-valued variants, where a constraint may extend
an already default value.

lib/spack/spack/solver/asp.py

@@ -1393,7 +1393,10 @@ def setup(self, driver, specs, tests=False):
             )
             for clause in self.spec_clauses(spec):
                 self.gen.fact(clause)
-
+                if clause.name == 'variant_set':
+                    self.gen.fact(fn.variant_default_value_from_cli(
+                        *clause.args
+                    ))
         self.gen.h1("Variant Values defined in specs")
         self.define_variant_values()
 

lib/spack/spack/solver/concretize.lp

@@ -403,14 +403,23 @@ variant_not_default(Package, Variant, Value, 0)
     external_with_variant_set(Package, Variant, Value),
     node(Package).
 
-% The default value for a variant in a package is what is written
+% The default value for a variant in a package is what is prescribed:
-% in the package.py file, unless some preference is set in packages.yaml
+%
+% 1. On the command line
+% 2. In packages.yaml (if there's no command line settings)
+% 3. In the package.py file (if there are no settings in
+%    packages.yaml and the command line)
+%
 variant_default_value(Package, Variant, Value)
  :- variant_default_value_from_package_py(Package, Variant, Value),
-    not variant_default_value_from_packages_yaml(Package, Variant, _).
+    not variant_default_value_from_packages_yaml(Package, Variant, _),
+    not variant_default_value_from_cli(Package, Variant, _).
 
 variant_default_value(Package, Variant, Value)
- :- variant_default_value_from_packages_yaml(Package, Variant, Value).
+ :- variant_default_value_from_packages_yaml(Package, Variant, Value),
+    not variant_default_value_from_cli(Package, Variant, _).
+
+variant_default_value(Package, Variant, Value) :- variant_default_value_from_cli(Package, Variant, Value).
 
 % Treat 'none' in a special way - it cannot be combined with other
 % values even if the variant is multi-valued
@@ -435,6 +444,7 @@ variant_single_value(Package, "dev_path")
 #defined variant_single_value/2.
 #defined variant_default_value/3.
 #defined variant_possible_value/3.
+#defined variant_default_value_from_cli/3.
 #defined variant_default_value_from_packages_yaml/3.
 #defined variant_default_value_from_package_py/3.
 #defined variant_value_from_disjoint_sets/4.
@@ -704,7 +714,7 @@ opt_criterion(14, "number of non-default variants (roots)").
 % If the value is a multivalued variant there could be multiple
 % values set as default. Since a default value has a weight of 0 we
 % need to maximize their number below to ensure they're all set
-opt_criterion(13, "multi-valued variants + preferred providers for roots").
+opt_criterion(13, "multi-valued variants").
 #minimize{ 0@13 : #true }.
 #maximize {
     1@13,Package,Variant,Value
@@ -712,8 +722,10 @@ opt_criterion(13, "multi-valued variants + preferred providers for roots").
     not variant_single_value(Package, Variant),
     root(Package)
 }.
+opt_criterion(12, "preferred providers for roots").
+#minimize{ 0@12 : #true }.
 #minimize{
-    Weight@13,Provider
+    Weight@12,Provider
     : provider_weight(Provider, Weight), root(Provider)
 }.
 

lib/spack/spack/test/concretize.py

@@ -1210,3 +1210,21 @@ def test_compiler_is_unique(self, spec_str, expected_compiler):
 
         for node in s.traverse():
             assert node.satisfies(expected_compiler)
+
+    @pytest.mark.parametrize('spec_str,expected_dict', [
+        # Check the defaults from the package (libs=shared)
+        ('multivalue-variant', {
+            'libs=shared': True,
+            'libs=static': False
+        }),
+        # Check that libs=static doesn't extend the default
+        ('multivalue-variant libs=static', {
+            'libs=shared': False,
+            'libs=static': True
+        }),
+    ])
+    def test_multivalued_variants_from_cli(self, spec_str, expected_dict):
+        s = Spec(spec_str).concretized()
+
+        for constraint, value in expected_dict.items():
+            assert s.satisfies(constraint) == value

var/spack/repos/builtin.mock/packages/multivalue-variant/package.py

@@ -29,6 +29,11 @@ class MultivalueVariant(Package):
         multi=False
     )
 
+    variant(
+        'libs', default='shared', values=('shared', 'static'), multi=True,
+        description='Type of libraries to install'
+    )
+
     depends_on('mpi')
     depends_on('callpath')
     depends_on('a')