variants: allow MultiValuedVariants to be constructed incrementally

lib/spack/spack/solver/asp.py

@@ -198,6 +198,11 @@ def spec_versions(self, spec):
             v for v in self.possible_versions[spec.name]
             if v.satisfies(spec.versions)
         ]
+
+        # don't bother restricting anything if all versions are allowed
+        if len(allowed_versions) == len(self.possible_versions[spec.name]):
+            return []
+
         predicates = [fn.version(spec.name, v) for v in allowed_versions]
 
         # conflict with any versions that do not satisfy the spec
@@ -288,9 +293,6 @@ def spec_clauses(self, spec):
         """
         clauses = []
 
-        if spec.name:
-            clauses.append(fn.node(spec.name))
-
         clauses.extend(self.spec_versions(spec))
 
         # seed architecture at the root (we'll propagate later)
@@ -428,8 +430,14 @@ def arch_target(self, pkg, target):
 
     def variant_value(self, pkg, name, value):
         pkg_class = spack.repo.path.get_pkg_class(pkg)
-        variant = pkg_class.variants[name].make_variant(value)
-        self._specs[pkg].variants[name] = variant
+
+        variant = self._specs[pkg].variants.get(name)
+        if variant:
+            # it's multi-valued
+            variant.append(value)
+        else:
+            variant = pkg_class.variants[name].make_variant(value)
+            self._specs[pkg].variants[name] = variant
 
     def version(self, pkg, version):
         self._specs[pkg].versions = ver([version])

lib/spack/spack/variant.py

@@ -389,6 +389,11 @@ def satisfies(self, other):
         return super_sat and (all(v in self.value for v in other.value) or
                               '*' in other or '*' in self)
 
+    def append(self, value):
+        """Add another value to this multi-valued variant."""
+        self._value = tuple(sorted((value,) + self._value))
+        self._original_value = ",".join(self._value)
+
 
 class SingleValuedVariant(AbstractVariant):
     """A variant that can hold multiple values, but one at a time."""