nag: added external detection capabilities (#18153)

var/spack/repos/builtin/packages/nag/package.py

@@ -2,9 +2,11 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
-
-from spack import *
 import os
+import re
+
+import spack.compiler
+import llnl.util.tty as tty
 
 
 class Nag(Package):
@@ -41,3 +43,60 @@ def install(self, spec, prefix):
     def setup_run_environment(self, env):
         env.set('F77', self.prefix.bin.nagfor)
         env.set('FC',  self.prefix.bin.nagfor)
+
+    executables = ['^nagfor$']
+
+    @classmethod
+    def determine_version(cls, exe):
+        version_regex = re.compile(r'NAG Fortran Compiler Release ([0-9.]+)')
+        # NAG does not support a flag that would enable verbose output and
+        # compilation/linking at the same time (with either '-#' or '-dryrun'
+        # the compiler only prints the commands but does not run them).
+        # Therefore, the only thing we can do is to pass the '-v' argument to
+        # the underlying GCC. In order to get verbose output from the latter
+        # at both compile and linking stages, we need to call NAG with two
+        # additional flags: '-Wc,-v' and '-Wl,-v'. However, we return only
+        # '-Wl,-v' for the following reasons:
+        #   1) the interface of this method does not support multiple flags in
+        #      the return value and, at least currently, verbose output at the
+        #      linking stage has a higher priority for us;
+        #   2) NAG is usually mixed with GCC compiler, which also accepts
+        #      '-Wl,-v' and produces meaningful result with it: '-v' is passed
+        #      to the linker and the latter produces verbose output for the
+        #      linking stage ('-Wc,-v', however, would break the compilation
+        #      with a message from GCC that the flag is not recognized).
+        #
+        # This way, we at least enable the implicit rpath detection, which is
+        # based on compilation of a C file (see method
+        # spack.compiler._get_compiler_link_paths): in the case of a mixed
+        # NAG/GCC toolchain, the flag will be passed to g++ (e.g.
+        # 'g++ -Wl,-v ./main.c'), otherwise, the flag will be passed to nagfor
+        # (e.g. 'nagfor -Wl,-v ./main.c' - note that nagfor recognizes '.c'
+        # extension and treats the file accordingly). The list of detected
+        # rpaths will contain only GCC-related directories and rpaths to
+        # NAG-related directories are injected by nagfor anyway.
+        try:
+            output = spack.compiler.get_compiler_version_output(exe, '-Wl,-v')
+            match = version_regex.search(output)
+            if match:
+                return match.group(1)
+        except spack.util.executable.ProcessError:
+            pass
+        except Exception as e:
+            tty.debug(e)
+
+    @classmethod
+    def determine_variants(cls, exes, version_str):
+        compilers = {}
+        for exe in exes:
+            if 'nagfor' in exe:
+                compilers['fortran'] = exe
+        return '', {'compilers': compilers}
+
+    @property
+    def fortran(self):
+        msg = "cannot retrieve Fortran compiler [spec is not concrete]"
+        assert self.spec.concrete, msg
+        if self.spec.external:
+            return self.spec.extra_attributes['compilers'].get('fortran', None)
+        return str(self.spec.prefix.bin.nagfor)