Proper error message when no subcommand is provided

On Python 3, invoking `pubs` would display a stacktrace, because
the subparser was not required.

This commit also simplifies the parser code by using .set_default()
to specify which command should be run.

This prompted changes in the plugin code. The code is still not
functioning, but many fixes in this commit bring the code closer
to a working state.

pubs/plugins.py

@@ -28,13 +28,13 @@ class PapersPlugin(object):
             raise RuntimeError("{} instance not created".format(cls.__name__))
 
 
-def load_plugins(ui, names):
+def load_plugins(conf, ui):
     """Imports the modules for a sequence of plugin names. Each name
     must be the name of a Python module under the "PLUGIN_NAMESPACE" namespace
     package in sys.path; the module indicated should contain the
     PapersPlugin subclasses desired.
     """
-    for name in names:
+    for name in conf['plugins']['active']:
         modname = '%s.%s.%s.%s' % ('pubs', PLUGIN_NAMESPACE, name, name)
         try:
             namespace = importlib.import_module(modname)
@@ -49,7 +49,7 @@ def load_plugins(ui, names):
                 if isinstance(obj, type) and issubclass(obj, PapersPlugin) \
                         and obj != PapersPlugin:
                     _classes.append(obj)
-                    _instances[obj] = obj()
+                    _instances[obj] = obj(conf)
 
 
 def get_plugins():

pubs/plugs/alias/alias.py

@@ -18,7 +18,7 @@ class Alias(object):
         p.add_argument('arguments', nargs='*',
                 help="arguments to be passed to the user defined command")
 
-    def run(self, args):
+    def command(self, conf, args):
         raise NotImplementedError
 
     @classmethod
@@ -35,7 +35,7 @@ class CommandAlias(Alias):
     - other arguments are passed to the command
     """
 
-    def run(self, args):
+    def command(self, conf, args):
         raw_args = ([args.prog]
                     + shlex.split(self.definition
                     + ' '
@@ -45,7 +45,7 @@ class CommandAlias(Alias):
 
 class ShellAlias(Alias):
 
-    def run(self, args):
+    def command(self, conf, args):
         """Uses a shell function so that arguments can be used in the command
         as shell arguments.
         """
@@ -59,12 +59,13 @@ class AliasPlugin(PapersPlugin):
 
     name = 'alias'
 
-    def __init__(self):
+    def __init__(self, conf):
         self.aliases = []
-        for name, definition in config('alias').items():
+        for name, definition in conf['alias'].items():
             self.aliases.append(Alias.create_alias(name, definition))
 
-    def get_commands(self, parser):
-        for a in self.aliases:
-            a.parser(parser)
-        return [(a.name, a.run) for a in self.aliases]
+    def update_parser(self, subparsers):
+        """Add subcommand to the provided subparser"""
+        for alias in self.aliases:
+            alias_parser = alias.parser(parser)
+            alias_parser.set_defaults(func=alias.command)

pubs/pubs_cmd.py

@@ -42,7 +42,7 @@ def execute(raw_args=sys.argv):
     else:
         conf_path = config.get_confpath(verify=False)  # will be checked on load
 
-    # loading config
+    # Loading config
     if len(remaining_args) > 0 and remaining_args[0] != 'init':
         try:
             conf = config.load_conf(path=conf_path, check=False)
@@ -63,19 +63,18 @@ def execute(raw_args=sys.argv):
                                      prog="pubs", add_help=True)
     parser.add_argument('--version', action='version', version=__version__)
     subparsers = parser.add_subparsers(title="valid commands", dest="command")
-    cmd_funcs = collections.OrderedDict()
+    subparsers.required = True
+
+    # Populate the parser with core commands
     for cmd_name, cmd_mod in CORE_CMDS.items():
-        cmd_mod.parser(subparsers)
-        cmd_funcs[cmd_name] = cmd_mod.command
+        cmd_parser = cmd_mod.parser(subparsers)
+        cmd_parser.set_defaults(func=cmd_mod.command)
 
     # Extend with plugin commands
-    plugins.load_plugins(ui, conf['plugins']['active'])
+    plugins.load_plugins(conf, ui)
     for p in plugins.get_plugins().values():
-        cmd_funcs.update(p.get_commands(subparsers))
+        p.update_parser(subparsers)
 
+    # Parse and run appropriate command
     args = parser.parse_args(remaining_args)
-    args.prog = parser.prog  # Hack: there might be a better way...
-    cmd = args.command
-    del args.command
-
-    cmd_funcs[cmd](conf, args)
+    args.func(conf, args)