Refactor module list command

CHANGELOG.md

@@ -1,6 +1,12 @@
 # Change Log
 All notable changes to this project will be documented in this file.
 
+## [Unreleased]
+### Added
+- Added command line argument --list-modules which will list modules
+  and exit. It can be followed by "essential" or "optional" to only
+  list those modules.
+
 ## [0.12.0] - 2016-12-08
 ### Added
 - Added screenshots to Readme.
@@ -163,6 +169,7 @@ All notable changes to this project will be documented in this file.
 - Fixed issue that could allow someone to start a module setup process
   without being logged in to Plinth.
 
+[Unreleased]: https://github.com/freedombox/Plinth/compare/v0.12.0...HEAD
 [0.12.0]: https://github.com/freedombox/Plinth/compare/v0.11.0...v0.12.0
 [0.11.0]: https://github.com/freedombox/Plinth/compare/v0.10.0...v0.11.0
 [0.10.0]: https://github.com/freedombox/Plinth/compare/v0.9.4...v0.10.0

plinth/__main__.py

@@ -65,7 +65,7 @@ def parse_arguments():
         help='list package dependencies for essential modules')
     parser.add_argument(
         '--list-modules', default=False, nargs='*',
-        help='list of enabled modules')
+        help='list modules')
 
     global arguments
     arguments = parser.parse_args()
@@ -288,20 +288,18 @@ def list_dependencies(module_list):
     sys.exit(error_code)
 
 
-def list_modules(modules_type) :
-    """List all enabled modules"""
+def list_modules(modules_type):
+    """List all/essential/optional modules and exit."""
     for module_name, module in module_loader.loaded_modules.items():
-        if modules_type:
-            if 'essential' in modules_type :
-                if getattr(module, 'is_essential', False) is True :
-                    print('{module_name}'.format(module_name=module_name))
-            else:
-                if getattr(module, 'is_essential', False) is False :
-                    print('{module_name}'.format(module_name=module_name))
-        else:
-            print('{module_name}'.format(module_name=module_name))
+        module_is_essential = getattr(module, 'is_essential', False)
+        if 'essential' in modules_type and not module_is_essential:
+            continue
+        elif 'optional' in modules_type and module_is_essential:
+            continue
+        print('{module_name}'.format(module_name=module_name))
     sys.exit()
 
+
 def run_diagnostics_and_exit():
     """Run diagostics on all modules and exit."""
     module = importlib.import_module('plinth.modules.diagnostics.diagnostics')
@@ -353,7 +351,6 @@ def main():
     if arguments.diagnose:
         run_diagnostics_and_exit()
 
-
     setup_server()
 
     cherrypy.engine.start()