spectrum-mpi: external support, compiler detection (#18055)

* spectrum-mpi: adding external support.

* Package is tested, works on LLNL lassen

* Spectrum external now detects the correct compiler

* Changing code to not output all compilers

Done per becker33's request on #18055

var/spack/repos/builtin/packages/spectrum-mpi/package.py

@@ -2,7 +2,8 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
-import os.path
+import os
+import re
 
 
 class SpectrumMpi(Package):
@@ -12,6 +13,82 @@ class SpectrumMpi(Package):
 
     provides('mpi')
 
+    executables = ['^ompi_info$']
+
+    @classmethod
+    def determine_version(cls, exe):
+        output = Executable(exe)(output=str, error=str)
+        match = re.search(r'Spectrum MPI: (\S+)', output)
+        if not match:
+            return None
+        version = match.group(1)
+        return version
+
+    @classmethod
+    def determine_variants(cls, exes, version):
+        compiler_suites = {
+            'xl': {'cc': 'mpixlc',
+                   'cxx': 'mpixlC',
+                   'f77': 'mpixlf',
+                   'fc': 'mpixlf'},
+            'pgi': {'cc': 'mpipgicc',
+                    'cxx': 'mpipgic++',
+                    'f77': 'mpipgifort',
+                    'fc': 'mpipgifort'},
+            'default': {'cc': 'mpicc',
+                        'cxx': 'mpicxx',
+                        'f77': 'mpif77',
+                        'fc': 'mpif90'}}
+
+        def get_host_compiler(exe):
+            output = Executable(exe)("--showme", output=str, error=str)
+            match = re.search(r'^(\S+)', output)
+            return match.group(1) if match else None
+
+        def get_spack_compiler_spec(compilers_found):
+            # check using cc for now, as everyone should have that defined.
+            path = os.path.dirname(compilers_found['cc'])
+            spack_compilers = spack.compilers.find_compilers([path])
+            actual_compiler = None
+            # check if the compiler actually matches the one we want
+            for spack_compiler in spack_compilers:
+                if os.path.dirname(spack_compiler.cc) == path:
+                    actual_compiler = spack_compiler
+                    break
+            return actual_compiler.spec if actual_compiler else None
+
+        results = []
+        for exe in exes:
+            dirname = os.path.dirname(exe)
+            siblings = os.listdir(dirname)
+            compilers_found = {}
+            for compiler_suite in compiler_suites.values():
+                for (compiler_class, compiler_name) in compiler_suite.items():
+                    if compiler_name in siblings:
+                        # Get the real name of the compiler
+                        full_exe = os.path.join(dirname, compiler_name)
+                        host_exe = get_host_compiler(full_exe)
+                        if host_exe:
+                            compilers_found[compiler_class] = host_exe
+                if compilers_found:
+                    break
+            if compilers_found:
+                compiler_spec = get_spack_compiler_spec(compilers_found)
+                if compiler_spec:
+                    variant = "%" + str(compiler_spec)
+                else:
+                    variant = ''
+                # Use this variant when you need to define the
+                # compilers explicitly
+                #
+                # results.append((variant, {'compilers': compilers_found}))
+                #
+                # Otherwise, use this simpler attribute
+                results.append(variant)
+            else:
+                results.append('')
+        return results
+
     def install(self, spec, prefix):
         raise InstallError('IBM MPI is not installable; it is vendor supplied')