Simply use class names as option help

The justification for this is that 1) the options are
already documented in the API documentation and 2) the
class names are fairly self-explanatory, so adding short
descriptions doesn't add much.

In the future, however, we could add a short description
by simply using the first line or sentence of the docstring;
note that docstrings would have to be canonicalized, which
they aren't now.

bin/mn

@@ -26,12 +26,13 @@ from mininet.log import lg, LEVELS, info, debug, warn, error
 from mininet.net import Mininet, MininetWithControlNet, VERSION
 from mininet.node import ( Host, CPULimitedHost, Controller, OVSController,
                            Ryu, NOX, RemoteController, findController,
-                           DefaultController,
+                           DefaultController, NullController,
                            UserSwitch, OVSSwitch, OVSBridge,
                            IVSSwitch )
 from mininet.nodelib import LinuxBridge
 from mininet.link import Link, TCLink, OVSLink
-from mininet.topo import SingleSwitchTopo, LinearTopo, SingleSwitchReversedTopo
+from mininet.topo import ( SingleSwitchTopo, LinearTopo,
+                           SingleSwitchReversedTopo, MinimalTopo )
 from mininet.topolib import TreeTopo, TorusTopo
 from mininet.util import customClass, specialClass, splitArgs
 from mininet.util import buildTopo
@@ -49,7 +50,7 @@ PLACEMENT = { 'block': SwitchBinPlacer, 'random': RandomPlacer }
 
 # built in topologies, created only when run
 TOPODEF = 'minimal'
-TOPOS = { 'minimal': lambda: SingleSwitchTopo( k=2 ),
+TOPOS = { 'minimal': MinimalTopo,
           'linear': LinearTopo,
           'reversed': SingleSwitchReversedTopo,
           'single': SingleSwitchTopo,
@@ -65,13 +66,6 @@ SWITCHES = { 'user': UserSwitch,
              'ivs': IVSSwitch,
              'lxbr': LinuxBridge,
              'default': OVSSwitch }
-SWITCHESHELP = { 'user': 'OpenFlow reference user-space switch.',
-                 'ovs': 'Open vSwitch OpenFlow-compatible switch.',
-                 'ovsbr': 'Open vSwitch as an L2 MAC learning switch.',
-                 'ovsk': 'Same as the ovs type.',
-                 'ivs': 'Indigo Virtual Switch.',
-                 'lxbr': 'Linux Bridge.',
-                 'default': 'Open vSwitch OpenFlow-compatible switch.'}
 
 HOSTDEF = 'proc'
 HOSTS = { 'proc': Host,
@@ -79,13 +73,14 @@ HOSTS = { 'proc': Host,
           'cfs': specialClass( CPULimitedHost, defaults=dict( sched='cfs' ) ) }
 
 CONTROLLERDEF = 'default'
+
 CONTROLLERS = { 'ref': Controller,
                 'ovsc': OVSController,
                 'nox': NOX,
                 'remote': RemoteController,
                 'ryu': Ryu,
                 'default': DefaultController,  # Note: replaced below
-                'none': lambda name: None }
+                'none': NullController }
 
 LINKDEF = 'default'
 LINKS = { 'default': Link,
@@ -103,20 +98,18 @@ ALTSPELLING = { 'pingall': 'pingAll',
                 'iperfUDP': 'iperfUdp' }
 
 
-def addDictOption( opts, choicesDict, default, name, helpDict=None, **kwargs ):
+def addDictOption( opts, choicesDict, default, name, **kwargs ):
     """Convenience function to add choices dicts to OptionParser.
        opts: OptionParser instance
        choicesDict: dictionary of valid choices, must include default
        default: default choice key
        name: long option name
-       helpDict: dictionary describing choices
        kwargs: additional arguments to add_option"""
     helpStr = ( '|'.join( sorted( choicesDict.keys() ) ) +
                 '[,param=value...]' )
-    if helpDict:
+    helpList = [ '%s=%s' % ( k, v.__name__ )
-        helpList = [ k + "=" + helpDict[k] 
+                 for k, v in choicesDict.items() ]
-                     for k in sorted( helpDict.keys() ) ]
+    helpStr += ' ' + ( ' '.join( helpList ) )
-        helpStr += " " + ( ' '.join( helpList ) )
     params = dict( type='string', default=default, help=helpStr )
     params.update( **kwargs )
     opts.add_option( '--' + name, **params )
@@ -202,7 +195,7 @@ class MininetRunner( object ):
                   '(type %prog -h for details)' )
 
         opts = OptionParser( description=desc, usage=usage )
-        addDictOption( opts, SWITCHES, SWITCHDEF, 'switch', SWITCHESHELP )
+        addDictOption( opts, SWITCHES, SWITCHDEF, 'switch' )
         addDictOption( opts, HOSTS, HOSTDEF, 'host' )
         addDictOption( opts, CONTROLLERS, [], 'controller', action='append' )
         addDictOption( opts, LINKS, LINKDEF, 'link' )

mininet/node.py

@@ -1517,3 +1517,7 @@ def DefaultController( name, controllers=DefaultControllers, **kwargs ):
     if not controller:
         raise Exception( 'Could not find a default OpenFlow controller' )
     return controller( name, **kwargs )
+
+def NullController( *_args, **_kwargs ):
+    "Nonexistent controller - simply returns None"
+    return None

mininet/topo.py

@@ -318,6 +318,12 @@ class SingleSwitchReversedTopo( Topo ):
                           port1=0, port2=( k - h + 1 ) )
 
 
+class MinimalTopo( SingleSwitchTopo ):
+    "Minimal topology with two hosts and one switch"
+    def build( self ):
+        return SingleSwitchTopo.build( self, k=2 )
+
+
 class LinearTopo( Topo ):
     "Linear topology of k switches, with n hosts per switch."