Add compiler usage tracking to concretize

This commit adds usage tracking for compiler packages to the
`workspace concretize` action. Warnings are now printed if a compiler is
defined in an object, and not used in one of the specs within an
experiment.

These errors are harder to track, as the defined compiler can come from
any of the experiment's objects (modifiers, etc..). But the
software-definitions command can help identify the unused compiler when
a warning is printed.

Author: douglasjacobsen

lib/ramble/ramble/workspace/workspace.py

@@ -1481,6 +1481,7 @@ def concretize(self, force=False, quiet=False):
             if app_inst.package_manager is None:
                 continue
 
+            compiler_packages = {}
             compiler_dicts = [app_inst.compilers]
             for mod_inst in app_inst._modifier_instances:
                 compiler_dicts.append(mod_inst.compilers)
@@ -1510,6 +1511,7 @@ def concretize(self, force=False, quiet=False):
                                 newly_created_packages.add(comp)
                                 packages_dict[comp] = syaml.syaml_dict()
 
+                            compiler_packages[comp] = False
                             packages_dict[comp].update(info.to_dict(prefix=spec_prefix))
                             for conf in info.config_opts():
                                 ramble.config.add(conf, scope=self.ws_file_config_scope_name())
@@ -1549,6 +1551,10 @@ def concretize(self, force=False, quiet=False):
                             ):
                                 packages_dict[spec_name] = syaml.syaml_dict()
 
+                            # Check for usage of compilers
+                            if info.compiler in compiler_packages:
+                                compiler_packages[info.compiler] = True
+
                             packages_dict[spec_name].update(info.to_dict(prefix=spec_prefix))
 
                             if spec_name not in app_packages:
@@ -1560,6 +1566,18 @@ def concretize(self, force=False, quiet=False):
 
                 environments_dict[env_name][namespace.packages] = app_packages.copy()
 
+            # Ensure all compilers in this experiment are used.
+            comp_list = []
+            for name, used in compiler_packages.items():
+                if not used:
+                    comp_list.append(name)
+            if comp_list:
+                logger.warn(
+                    "Unused compiler(s) found in experiment: "
+                    + app_inst.expander.experiment_namespace
+                )
+                logger.warn(f"   {comp_list}")
+
         ramble.config.config.update_config(
             namespace.software, full_software_dict, scope=self.ws_file_config_scope_name()
         )