Change how configure gets compiler/mpilib/debug.

These are now passed in via environment variables, or set using the
machine default, rather than using a `--shell-opts` argument.

tools/configure

@@ -27,7 +27,13 @@ The pieces of information that will be written include:
 
 1. Machine-specific build settings (i.e. the "Macros" file).
 2. File-specific build settings (i.e. "Depends" files).
-3. Environment variable loads (i.e. the env_mach_specific file).
+3. Environment variable loads (i.e. the env_mach_specific files).
+
+The .env_mach_specific.sh and .env_mach_specific.csh files are specific to a
+given compiler, MPI library, and DEBUG setting. By default, these will be the
+machine's default compiler, the machine's default MPI library, and FALSE,
+respectively. These can be changed by setting the environment variables
+COMPILER, MPILIB, and DEBUG, respectively.
 """
     parser = argparse.ArgumentParser(description=description)
     CIME.utils.setup_standard_logging_options(parser)
@@ -51,30 +57,23 @@ The pieces of information that will be written include:
     parser.add_argument("--output-dir", default=os.getcwd(),
                         help="The directory to write files to. If not "
                         "specified, defaults to the current working directory.")
-    parser.add_argument("--shell-opts",
-                        help="Specification of the build configuration to "
-                        "generate env_mach_specific shell scripts for. This "
-                        "should be of the form COMPILER,MPILIB,DEBUG. "
-                        "For example, 'intel,mpich2,true' is a valid setting "
-                        "for this option, as long as ICC and MPICH2 are "
-                        "available on this machine. If this option is not "
-                        "specified, only the XML file is generated (mainly for "
-                        "documentation/testing), with no shell scripts.")
 
     args = parser.parse_args()
     CIME.utils.handle_standard_logging_options(args)
 
     opts = {}
     if args.machines_dir is not None:
         machines_file = os.path.join(args.machines_dir, "config_machines.xml")
-        opts['machobj'] = Machines(infile=machines_file, machine=args.machine)
+        machobj = Machines(infile=machines_file, machine=args.machine)
     else:
         if os.environ.get('CIME_MODEL') is not None:
-            opts['machobj'] = Machines(machine=args.machine)
+            machobj = Machines(machine=args.machine)
         else:
             expect(False, "Either --mach-dir or the CIME_MODEL environment "
                    "variable must be specified!")
 
+    opts['machobj'] = machobj
+
     if args.macros_format is None:
         opts['macros_format'] = []
     else:
@@ -85,23 +84,38 @@ The pieces of information that will be written include:
 
     opts['output_dir'] = args.output_dir
 
-    if args.shell_opts is not None:
-        compiler, mpilib, debug = tuple(args.shell_opts.split(","))
-        expect(opts['machobj'].is_valid_compiler(compiler),
-               "Invalid compiler vender passed in --shell-opts: %s" % compiler)
-        opts['compiler'] = compiler
-        expect(opts['machobj'].is_valid_MPIlib(mpilib),
-               "Invalid MPI library name passed in --shell-opts: %s" % mpilib)
-        opts['mpilib'] = mpilib
-        debug_normed = debug.lower()
-        if debug_normed == "true":
-            opts['debug'] = True
-        elif debug_normed == "false":
-            opts['debug'] = False
-        else:
-            expect(False,
-                   "Invalid DEBUG value passed in --shell-opts "
-                   "(must be true or false): %s" % debug)
+    # Set compiler.
+    if "COMPILER" in os.environ:
+        compiler = os.environ["COMPILER"]
+    else:
+        compiler = machobj.get_default_compiler()
+        os.environ["COMPILER"] = compiler
+    expect(opts['machobj'].is_valid_compiler(compiler),
+           "Invalid compiler vendor given in COMPILER environment variable: %s"
+           % compiler)
+    opts['compiler'] = compiler
+
+    # Set MPI library.
+    if "MPILIB" in os.environ:
+        mpilib = os.environ["MPILIB"]
+    else:
+        mpilib = machobj.get_default_MPIlib()
+        os.environ["MPILIB"] = mpilib
+    expect(opts['machobj'].is_valid_MPIlib(mpilib),
+           "Invalid MPI library name given in MPILIB environment variable: %s" %
+           mpilib)
+    opts['mpilib'] = mpilib
+
+    # Set DEBUG flag.
+    if "DEBUG" in os.environ:
+        expect(os.environ["DEBUG"].lower() in ('true', 'false'),
+               "Invalid DEBUG environment variable value (must be 'TRUE' or "
+               "'FALSE'): %s" % os.environ["DEBUG"])
+        debug = os.environ["DEBUG"].lower() == "true"
+    else:
+        debug = False
+        os.environ["DEBUG"] = "FALSE"
+    opts['debug'] = debug
 
     return opts
 
@@ -133,13 +147,15 @@ def _main():
             shutil.copy(compiler_depends, output_dir)
 
     # env_mach_specific generation.
+    ems_path = os.path.join(output_dir, "env_mach_specific.xml")
+    if os.path.exists(ems_path):
+        os.remove(ems_path)
     ems_file = EnvMachSpecific(output_dir)
     ems_file.populate(machobj)
     ems_file.write()
-    if 'compiler' in opts:
-        for shell in ('sh', 'csh'):
-            ems_file.make_env_mach_specific_file(opts['compiler'], opts['debug'],
-                                                 opts['mpilib'], shell)
+    for shell in ('sh', 'csh'):
+        ems_file.make_env_mach_specific_file(opts['compiler'], opts['debug'],
+                                             opts['mpilib'], shell)
 
 
 if __name__ == "__main__":