1 """The `command` module provides :class:`Command`\s and
2 :class:`Argument`\s for defining commands.
8 class CommandExit (Exception):
10 return self.__class__.__name__
12 class Success (CommandExit):
15 class Failure (CommandExit):
18 class Command (object):
19 """One-line command description here.
21 >>> c = Command(name='test', help='An example Command.')
22 >>> status = c.run(NullQueue(), PrintQueue(), help=True) # doctest: +REPORT_UDIFF
27 help BOOL (bool) Print a help message.
33 def __init__(self, name, aliases=None, arguments=[], help=''):
37 self.aliases = aliases
39 Argument(name='help', type='bool', default=False, count=1,
40 callback=StoreValue(True), help='Print a help message.'),
44 def run(self, inqueue=None, outqueue=None, **kwargs):
45 """`Normalize inputs and handle <Argument help> before punting
51 outqueue = NullQueue()
53 params = self.handle_arguments(inqueue, outqueue, kwargs)
54 if params['help'] == True:
55 outqueue.put(self.help())
57 self._run(inqueue, outqueue, params)
58 except CommandExit, e:
59 if isinstance(e, Failure):
60 outqueue.put(e.message)
66 def _run(self, inqueue, outqueue, params):
67 """This is where the command-specific magic will happen.
71 def handle_arguments(self, inqueue, outqueue, params):
72 """Normalize and validate input parameters (:class:`Argument` values).
74 for argument in self.arguments:
75 names = [argument.name] + argument.aliases
76 settings = [(name,v) for name,v in params.items() if name in names]
77 if len(settings) == 0:
78 if argument.optional == True or argument.count == 0:
79 settings = [(argument.name, argument.default)]
81 raise Failure('Required argument %s not set.'
84 raise Failure('Multiple settings for %s:\n %s'
86 '\n '.join(['%s: %s' % (name,value)
87 for name,value in sorted(settings)])))
88 name,value = settings[0]
89 if name != argument.name:
91 params[argument.name] = value
92 if argument.callback != None:
93 value = argument.callback(self, argument, value)
94 params[argument.name] = value
95 argument.validate(value)
98 def help(self, *args):
99 name_part = 'Command: %s' % self.name
100 if len(self.aliases) > 0:
101 name_part += ' (%s)' % ', '.join(self.aliases)
102 argument_part = ['Arguments:'] + [a.help() for a in self.arguments]
103 argument_part = '\n'.join(argument_part)
104 help_part = self._help
105 return '\n\n'.join([name_part, argument_part, help_part])
107 class Argument (object):
108 """Structured user input for :class:`Command`\s.
110 TODO: ranges for `count`?
112 def __init__(self, name, aliases=None, type='string', metavar=None,
113 default=None, optional=True, count=1,
114 completion_callback=None, callback=None, help=''):
118 self.aliases = aliases
121 metavar = type.upper()
122 self.metavar = metavar
123 self.default = default
124 self.optional = optional
126 self.completion_callback = completion_callback
127 self.callback = callback
131 return '<%s %s>' % (self.__class__.__name__, self.name)
134 return self.__str__()
137 parts = ['%s ' % self.name]
138 if self.metavar != None:
139 parts.append('%s ' % self.metavar)
140 parts.extend(['(%s) ' % self.type, self._help])
141 return ''.join(parts)
143 def validate(self, value):
144 """If `value` is not appropriate, raise `ValueError`.
146 pass # TODO: validation
148 # TODO: type conversion
150 # TODO: type extensions?
154 class StoreValue (object):
155 def __init__(self, value):
157 def __call__(self, command, argument, fragment=None):
160 class NullQueue (queue.Queue):
161 """The :class:`queue.Queue` equivalent of `/dev/null`.
163 This is a bottomless pit. Items go in, but never come out.
165 def get(self, block=True, timeout=None):
166 """Raise queue.Empty.
168 There's really no need to override the base Queue.get, but I
169 want to know if someone tries to read from a NullQueue. With
170 the default implementation they would just block silently
175 def put(self, item, block=True, timeout=None):
176 """Dump an item into the void.
178 Block and timeout are meaningless, because there is always a
179 free slot available in a bottomless pit.
183 class PrintQueue (NullQueue):
184 """Debugging :class:`NullQueue` that prints items before dropping
187 def put(self, item, block=True, timeout=None):
188 """Print `item` and then dump it into the void.
190 print 'ITEM:\n%s' % item