Obtains default modules from a clean subshell.

The list of default environment modules is obtained by calling

`module list -lt`

from a subshell with a wiped environment. This allows `/etc/profile` and other
init scripts to be fully sourced which should generally include loading the
default modules.

The list of default modules is then parsed for the first acceptable CPU target,
assumed to be the back_end target.

lib/spack/spack/platforms/cray.py

@@ -1,6 +1,7 @@
 import os
 import re
 import spack.config
+from spack.util.executable import which
 from spack.architecture import Platform, Target, NoPlatformError
 from spack.operating_systems.linux_distro import LinuxDistro
 from spack.operating_systems.cnl import Cnl
@@ -10,15 +11,35 @@
 NON_TARGETS = ('hugepages', 'network', 'target', 'accel', 'xtpe')
 
 
-def _target_from_init(name):
+def _target_from_clean_env(name):
-    matches = []
+    '''Return the default back_end target as loaded in a clean login session.
+
+    A bash subshell is launched with a wiped environment and the list of loaded
+    modules is parsed for the first acceptable CrayPE target.
+    '''
+    # Based on the incantation:
+    # echo "$(env - USER=$USER /bin/bash -l -c 'module list -lt')"
+    default_modules = []
+    targets = []
     if name != 'front_end':
+        env = which('env')
+        env.add_default_arg('-')
+        # CAUTION - $USER is generally needed to initialize the environment.
+        # There may be other variables needed for general success.
+        output = env('USER=%s' % os.environ['USER'],
+                    '/bin/bash', '-l', '-c', 'module list -lt',
+                    output=str, error=str)
         pattern = 'craype-(?!{0})(\S*)'.format('|'.join(NON_TARGETS))
-        with open('/etc/bash.bashrc.local', 'r') as conf:
+        for line in output.splitlines():
-            for line in conf:
+            if 'craype-' in line:
-                if re.search('^[^\#]*module[\s]*(?:add|load)', line):
+                targets.extend(re.findall(pattern, line))
-                    matches.extend(re.findall(pattern, line))
+            if len(line.split()) == 1:
-    return matches[0] if matches else None
+                default_modules.append(line)
+        # if default_modules:
+        #     print 'Found default modules:'
+        #     for defmod in default_modules:
+        #         print '    ', defmod
+    return targets[0] if targets else None
 
 
 class Cray(Platform):
@@ -45,7 +66,7 @@ def __init__(self):
             if _target is None:
                 _target = conf.get(name)
             if _target is None:
-                _target = _target_from_init(name)
+                _target = _target_from_clean_env(name)
             setattr(self, name, _target)
 
             if _target is not None: