Allow for packages with multiple build-systems (#30738)

This commit extends the DSL that can be used in packages
to allow declaring that a package uses different build-systems
under different conditions.

It requires each spec to have a `build_system` single valued
variant. The variant can be used in many context to query, manipulate
or select the build system associated with a concrete spec.

The knowledge to build a package has been moved out of the
PackageBase hierarchy, into a new Builder hierarchy. Customization
of the default behavior for a given builder can be obtained by
coding a new derived builder in package.py.

The "run_after" and "run_before" decorators are now applied to
methods on the builder. They can also incorporate a "when="
argument to specify that a method is run only when certain
conditions apply.

For packages that do not define their own builder, forwarding logic
is added between the builder and package (methods not found in one
will be retrieved from the other); this PR is expected to be fully
backwards compatible with unmodified packages that use a single
build system.

1 files changed, 27 insertions, 28 deletions

diff --git a/var/spack/repos/builtin/packages/quantum-espresso/package.py b/var/spack/repos/builtin/packages/quantum-espresso/package.py
index acc07692cf..47fb80e6f9 100644
--- a/var/spack/repos/builtin/packages/quantum-espresso/package.py
+++ b/var/spack/repos/builtin/packages/quantum-espresso/package.py
@@ -2,11 +2,12 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
-
+import spack.build_systems.cmake
+import spack.build_systems.generic
 from spack.package import *
 
 
-class QuantumEspresso(CMakePackage):
+class QuantumEspresso(CMakePackage, Package):
     """Quantum ESPRESSO is an integrated suite of Open-Source computer codes
     for electronic-structure calculations and materials modeling at the
     nanoscale. It is based on density-functional theory, plane waves, and
@@ -19,6 +20,8 @@ class QuantumEspresso(CMakePackage):
 
     maintainers = ["ye-luo", "danielecesarini", "bellenlau"]
 
+    build_system(conditional("cmake", when="@6.8:"), "generic", default="cmake")
+
     version("develop", branch="develop")
     version("7.1", sha256="d56dea096635808843bd5a9be2dee3d1f60407c01dbeeda03f8256a3bcfc4eb6")
     version("7.0", sha256="85beceb1aaa1678a49e774c085866d4612d9d64108e0ac49b23152c8622880ee")
@@ -56,10 +59,8 @@ class QuantumEspresso(CMakePackage):
         destination=".",
     )
 
-    variant("cmake", default=True, description="Builds via CMake")
-    with when("+cmake"):
+    with when("build_system=cmake"):
         depends_on("cmake@3.14.0:", type="build")
-        conflicts("@:6.7", msg="+cmake works since QE v6.8")
 
     variant("libxc", default=False, description="Uses libxc")
     depends_on("libxc@5.1.2:", when="+libxc")
@@ -93,7 +94,7 @@ class QuantumEspresso(CMakePackage):
                     msg="bugs with NVHPCSDK from v21.11 to v22.3, OpenMP and GPU",
                 )
             # only cmake is supported
-            conflicts("~cmake", msg="Only CMake supported for GPU-enabled version")
+            conflicts("build_system=generic", msg="Only CMake supported for GPU-enabled version")
 
     # NVTX variant for profiling
     # requires linking to CUDA runtime APIs , handled by CMake
@@ -121,9 +122,10 @@ class QuantumEspresso(CMakePackage):
 
     with when("+elpa"):
         # CMake builds only support elpa without openmp
-        depends_on("elpa~openmp", when="+cmake")
-        depends_on("elpa+openmp", when="+openmp~cmake")
-        depends_on("elpa~openmp", when="~openmp~cmake")
+        depends_on("elpa~openmp", when="build_system=cmake")
+        with when("build_system=generic"):
+            depends_on("elpa+openmp", when="+openmp")
+            depends_on("elpa~openmp", when="~openmp")
         # Elpa is formally supported by @:5.4.0, but QE configure searches
         # for it in the wrong folders (or tries to download it within
         # the build directory). Instead of patching Elpa to provide the
@@ -181,12 +183,14 @@ class QuantumEspresso(CMakePackage):
         with when("@7.0.1:"):
             # when QE doesn't use hdf5 library, the converter plugin still needs it
             depends_on("hdf5@1.8.16:+hl~mpi", when="hdf5=none")
-            conflicts("~cmake", msg="QE-to-QMCPACK wave function converter requires cmake")
+            conflicts(
+                "build_system=generic", msg="QE-to-QMCPACK wave function converter requires cmake"
+            )
 
     # Enables building Electron-phonon Wannier 'epw.x' executable
     # http://epw.org.uk/Main/About
-    variant("epw", default=False, description="Builds Electron-phonon Wannier executable")
-    conflicts("~epw", when="+cmake", msg="epw cannot be turned off when using CMake")
+    variant("epw", default=True, description="Builds Electron-phonon Wannier executable")
+    conflicts("~epw", when="build_system=cmake", msg="epw cannot be turned off when using CMake")
 
     with when("+epw"):
         # The first version of Q-E to feature integrated EPW is 6.0.0,
@@ -198,8 +202,10 @@ class QuantumEspresso(CMakePackage):
         # Constraints may be relaxed as successful reports
         # of different compiler+mpi combinations arrive
 
-        # TODO: enable building EPW when ~mpi and ~cmake
-        conflicts("~mpi", when="~cmake", msg="EPW needs MPI when ~cmake")
+        # TODO: enable building EPW when ~mpi and build_system=generic
+        conflicts(
+            "~mpi", when="build_system=generic", msg="EPW needs MPI when build_system=generic"
+        )
 
         # EPW doesn't gets along well with OpenMPI 2.x.x
         conflicts("^openmpi@2.0.0:2", msg="OpenMPI version incompatible with EPW")
@@ -212,19 +218,19 @@ class QuantumEspresso(CMakePackage):
     variant(
         "environ",
         default=False,
+        when="build_system=generic",
         description="Enables support for introducing environment effects "
         "into atomistic first-principles simulations."
         "See http://quantum-environ.org/about.html",
     )
-    conflicts("+environ", when="+cmake", msg="environ doesn't work with CMake")
 
     variant(
         "gipaw",
         default=False,
+        when="build_system=generic",
         description="Builds Gauge-Including Projector Augmented-Waves executable",
     )
     with when("+gipaw"):
-        conflicts("+cmake", msg="gipaw doesn't work with CMake")
         conflicts(
             "@:6.3", msg="gipaw standard support available for QE 6.3 or grater version only"
         )
@@ -370,6 +376,8 @@ class QuantumEspresso(CMakePackage):
     # extlibs_makefile updated to work with fujitsu compilers
     patch("fj-fox.patch", when="+patch %fj")
 
+
+class CMakeBuilder(spack.build_systems.cmake.CMakeBuilder):
     def cmake_args(self):
         spec = self.spec
 
@@ -400,18 +408,9 @@ class QuantumEspresso(CMakePackage):
 
         return cmake_args
 
-    @when("~cmake")
-    def cmake(self, spec, prefix):
-        print("Bypass cmake stage when building via configure")
-
-    @when("~cmake")
-    def build(self, spec, prefix):
-        print("Bypass build stage when building via configure")
-
-    @when("~cmake")
-    def install(self, spec, prefix):
-        print("Override install stage when building via configure")
 
+class GenericBuilder(spack.build_systems.generic.GenericBuilder):
+    def install(self, pkg, spec, prefix):
         prefix_path = prefix.bin if "@:5.4.0" in spec else prefix
         options = ["-prefix={0}".format(prefix_path)]
 
@@ -577,7 +576,7 @@ class QuantumEspresso(CMakePackage):
         # can't be applied to the '+qmcpack' variant
         if spec.variants["hdf5"].value != "none":
             if spec.satisfies("@6.1.0:6.4.0") or (spec.satisfies("@6.4.1") and "+qmcpack" in spec):
-                make_inc = join_path(self.stage.source_path, "make.inc")
+                make_inc = join_path(self.pkg.stage.source_path, "make.inc")
                 zlib_libs = spec["zlib"].prefix.lib + " -lz"
                 filter_file(zlib_libs, format(spec["zlib"].libs.ld_flags), make_inc)