CMakePackage: convert variants to CMake arguments (#14376)

Add a 'define_from_variant` helper function to CMake-based Spack
packages to convert package variants into CMake arguments. For
example:

  args.append('-DFOO=%s' % ('ON' if '+foo' in self.spec else 'OFF'))

can be replaced with:

  args.append(self.define_from_variant('foo'))

The following conversions are handled automatically:

* Flag variants will be converted to CMake booleans
* Multivalued variants will be converted to semicolon-separated strings
* Other variant values are converted to CMake string arguments

This also adds a 'define' helper method to convert any variable to
a CMake argument. It has the same conversion rules as
'define_from_variant' (but operates directly on values rather than
requiring the user to supply the name of a package variant).

4 files changed, 161 insertions, 16 deletions

diff --git a/lib/spack/docs/build_systems/cmakepackage.rst b/lib/spack/docs/build_systems/cmakepackage.rst
index 0a771edad3..76e89c80b1 100644
--- a/lib/spack/docs/build_systems/cmakepackage.rst
+++ b/lib/spack/docs/build_systems/cmakepackage.rst
@@ -128,17 +128,20 @@ Adding flags to cmake
 ^^^^^^^^^^^^^^^^^^^^^
 
 To add additional flags to the ``cmake`` call, simply override the
-``cmake_args`` function:
+``cmake_args`` function. The following example defines values for the flags
+``WHATEVER``, ``ENABLE_BROKEN_FEATURE``, ``DETECT_HDF5``, and ``THREADS`` with
+and without the :py:meth:`~.CMakePackage.define` and
+:py:meth:`~.CMakePackage.define_from_variant` helper functions:
 
 .. code-block:: python
 
    def cmake_args(self):
-       args = []
-
-       if '+hdf5' in self.spec:
-           args.append('-DDETECT_HDF5=ON')
-       else:
-           args.append('-DDETECT_HDF5=OFF')
+       args = [
+           '-DWHATEVER:STRING=somevalue',
+           self.define('ENABLE_BROKEN_FEATURE', False),
+           self.define_from_variant('DETECT_HDF5', 'hdf5'),
+           self.define_from_variant('THREADS'), # True if +threads
+       ]
 
        return args
 
diff --git a/lib/spack/spack/build_systems/cmake.py b/lib/spack/spack/build_systems/cmake.py
index 14f33e94e6..d7da957a9d 100644
--- a/lib/spack/spack/build_systems/cmake.py
+++ b/lib/spack/spack/build_systems/cmake.py
@@ -147,33 +147,129 @@ class CMakePackage(PackageBase):
         except KeyError:
             build_type = 'RelWithDebInfo'
 
+        define = CMakePackage.define
         args = [
             '-G', generator,
-            '-DCMAKE_INSTALL_PREFIX:PATH={0}'.format(pkg.prefix),
-            '-DCMAKE_BUILD_TYPE:STRING={0}'.format(build_type),
+            define('CMAKE_INSTALL_PREFIX', pkg.prefix),
+            define('CMAKE_BUILD_TYPE', build_type),
         ]
 
         if primary_generator == 'Unix Makefiles':
-            args.append('-DCMAKE_VERBOSE_MAKEFILE:BOOL=ON')
+            args.append(define('CMAKE_VERBOSE_MAKEFILE', True))
 
         if platform.mac_ver()[0]:
             args.extend([
-                '-DCMAKE_FIND_FRAMEWORK:STRING=LAST',
-                '-DCMAKE_FIND_APPBUNDLE:STRING=LAST'
+                define('CMAKE_FIND_FRAMEWORK', "LAST"),
+                define('CMAKE_FIND_APPBUNDLE', "LAST"),
             ])
 
         # Set up CMake rpath
-        args.append('-DCMAKE_INSTALL_RPATH_USE_LINK_PATH:BOOL=FALSE')
-        rpaths = ';'.join(spack.build_environment.get_rpaths(pkg))
-        args.append('-DCMAKE_INSTALL_RPATH:STRING={0}'.format(rpaths))
+        args.extend([
+            define('CMAKE_INSTALL_RPATH_USE_LINK_PATH', False),
+            define('CMAKE_INSTALL_RPATH',
+                   spack.build_environment.get_rpaths(pkg)),
+        ])
         # CMake's find_package() looks in CMAKE_PREFIX_PATH first, help CMake
         # to find immediate link dependencies in right places:
         deps = [d.prefix for d in
                 pkg.spec.dependencies(deptype=('build', 'link'))]
         deps = filter_system_paths(deps)
-        args.append('-DCMAKE_PREFIX_PATH:STRING={0}'.format(';'.join(deps)))
+        args.append(define('CMAKE_PREFIX_PATH', deps))
         return args
 
+    @staticmethod
+    def define(cmake_var, value):
+        """Return a CMake command line argument that defines a variable.
+
+        The resulting argument will convert boolean values to OFF/ON
+        and lists/tuples to CMake semicolon-separated string lists. All other
+        values will be interpreted as strings.
+
+        Examples:
+
+            .. code-block:: python
+
+                [define('BUILD_SHARED_LIBS', True),
+                 define('CMAKE_CXX_STANDARD', 14),
+                 define('swr', ['avx', 'avx2'])]
+
+            will generate the following configuration options:
+
+            .. code-block:: console
+
+                ["-DBUILD_SHARED_LIBS:BOOL=ON",
+                 "-DCMAKE_CXX_STANDARD:STRING=14",
+                 "-DSWR:STRING=avx;avx2]
+
+        """
+        # Create a list of pairs. Each pair includes a configuration
+        # option and whether or not that option is activated
+        if isinstance(value, bool):
+            kind = 'BOOL'
+            value = "ON" if value else "OFF"
+        else:
+            kind = 'STRING'
+            if isinstance(value, (list, tuple)):
+                value = ";".join(str(v) for v in value)
+            else:
+                value = str(value)
+
+        return "".join(["-D", cmake_var, ":", kind, "=", value])
+
+    def define_from_variant(self, cmake_var, variant=None):
+        """Return a CMake command line argument from the given variant's value.
+
+        The optional ``variant`` argument defaults to the lower-case transform
+        of ``cmake_var``.
+
+        This utility function is similar to
+        :py:meth:`~.AutotoolsPackage.with_or_without`.
+
+        Examples:
+
+            Given a package with:
+
+            .. code-block:: python
+
+                variant('cxxstd', default='11', values=('11', '14'),
+                        multi=False, description='')
+                variant('shared', default=True, description='')
+                variant('swr', values=any_combination_of('avx', 'avx2'),
+                        description='')
+
+            calling this function like:
+
+            .. code-block:: python
+
+                [define_from_variant('BUILD_SHARED_LIBS', 'shared'),
+                 define_from_variant('CMAKE_CXX_STANDARD', 'cxxstd'),
+                 define_from_variant('SWR')]
+
+            will generate the following configuration options:
+
+            .. code-block:: console
+
+                ["-DBUILD_SHARED_LIBS:BOOL=ON",
+                 "-DCMAKE_CXX_STANDARD:STRING=14",
+                 "-DSWR:STRING=avx;avx2]
+
+            for ``<spec-name> cxxstd=14 +shared swr=avx,avx2``
+        """
+
+        if variant is None:
+            variant = cmake_var.lower()
+
+        if variant not in self.variants:
+            raise KeyError(
+                '"{0}" is not a variant of "{1}"'.format(variant, self.name))
+
+        value = self.spec.variants[variant].value
+        if isinstance(value, (tuple, list)):
+            # Sort multi-valued variants for reproducibility
+            value = sorted(value)
+
+        return self.define(cmake_var, value)
+
     def flags_to_build_system_args(self, flags):
         """Produces a list of all command line arguments to pass the specified
         compiler flags to cmake. Note CMAKE does not have a cppflags option,
diff --git a/lib/spack/spack/test/build_systems.py b/lib/spack/spack/test/build_systems.py
index 744821a04e..7ede78b7a5 100644
--- a/lib/spack/spack/test/build_systems.py
+++ b/lib/spack/spack/test/build_systems.py
@@ -181,3 +181,41 @@ class TestAutotoolsPackage(object):
         assert '--without-bar' in options
         assert '--without-baz' in options
         assert '--no-fee' in options
+
+
+@pytest.mark.usefixtures('config', 'mock_packages')
+class TestCMakePackage(object):
+
+    def test_define(self):
+        s = Spec('cmake-client')
+        s.concretize()
+        pkg = spack.repo.get(s)
+
+        for cls in (list, tuple):
+            arg = pkg.define('MULTI', cls(['right', 'up']))
+            assert arg == '-DMULTI:STRING=right;up'
+
+        arg = pkg.define('ENABLE_TRUTH', False)
+        assert arg == '-DENABLE_TRUTH:BOOL=OFF'
+        arg = pkg.define('ENABLE_TRUTH', True)
+        assert arg == '-DENABLE_TRUTH:BOOL=ON'
+
+        arg = pkg.define('SINGLE', 'red')
+        assert arg == '-DSINGLE:STRING=red'
+
+    def test_define_from_variant(self):
+        s = Spec('cmake-client multi=up,right ~truthy single=red')
+        s.concretize()
+        pkg = spack.repo.get(s)
+
+        arg = pkg.define_from_variant('MULTI')
+        assert arg == '-DMULTI:STRING=right;up'
+
+        arg = pkg.define_from_variant('ENABLE_TRUTH', 'truthy')
+        assert arg == '-DENABLE_TRUTH:BOOL=OFF'
+
+        arg = pkg.define_from_variant('SINGLE')
+        assert arg == '-DSINGLE:STRING=red'
+
+        with pytest.raises(KeyError, match="not a variant"):
+            pkg.define_from_variant('NONEXISTENT')
diff --git a/var/spack/repos/builtin.mock/packages/cmake-client/package.py b/var/spack/repos/builtin.mock/packages/cmake-client/package.py
index 286ee08086..2350259b22 100644
--- a/var/spack/repos/builtin.mock/packages/cmake-client/package.py
+++ b/var/spack/repos/builtin.mock/packages/cmake-client/package.py
@@ -21,6 +21,14 @@ class CmakeClient(CMakePackage):
 
     version('1.0', '4cb3ff35b2472aae70f542116d616e63')
 
+    variant(
+        'multi', description='',
+        values=any_combination_of('up', 'right', 'back').with_default('up')
+    )
+    variant('single', description='', default='blue',
+            values=('blue', 'red', 'green'), multi=False)
+    variant('truthy', description='', default=True)
+
     callback_counter = 0
 
     flipped = False