Splice differing virtual packages (#27919)

Co-authored-by: Nathan Hanford <hanford1@llnl.gov>

var/spack/repos/builtin.mock/packages/splice-a/package.py

@@ -0,0 +1,30 @@
+# Copyright 2013-2021 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 import *
+
+
+class SpliceA(Package):
+    """Simple package with one optional dependency"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/splice-a-1.0.tar.gz"
+
+    version('1.0', '0123456789abcdef0123456789efghij')
+
+    variant('foo', default=False, description='nope')
+    variant('bar', default=False, description='nope')
+    variant('baz', default=False, description='nope')
+
+    depends_on('splice-z')
+    depends_on('splice-z+foo', when='+foo')
+
+    provides('something')
+    provides('somethingelse')
+
+    def install(self, spec, prefix):
+        with open(prefix.join('splice-a'), 'w') as f:
+            f.write('splice-a: {0}'.format(prefix))
+            f.write('splice-z: {0}'.format(spec['splice-z'].prefix))

var/spack/repos/builtin.mock/packages/splice-h/package.py

@@ -21,6 +21,9 @@ class SpliceH(Package):
     depends_on('splice-z')
     depends_on('splice-z+foo', when='+foo')
 
+    provides('something')
+    provides('somethingelse')
+
     def install(self, spec, prefix):
         with open(prefix.join('splice-h'), 'w') as f:
             f.write('splice-h: {0}'.format(prefix))

var/spack/repos/builtin.mock/packages/splice-vh/package.py

@@ -0,0 +1,29 @@
+# Copyright 2013-2022 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 import *
+
+
+class SpliceVh(Package):
+    """Simple package with one optional dependency"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/splice-vh-1.0.tar.gz"
+
+    version('1.0', '0123456789abcdef0123456789abcdef')
+
+    variant('foo', default=False, description='nope')
+    variant('bar', default=False, description='nope')
+    variant('baz', default=False, description='nope')
+
+    depends_on('splice-z')
+    depends_on('splice-z+foo', when='+foo')
+
+    provides('something')
+
+    def install(self, spec, prefix):
+        with open(prefix.join('splice-vh'), 'w') as f:
+            f.write('splice-vh: {0}'.format(prefix))
+            f.write('splice-z: {0}'.format(spec['splice-z'].prefix))