1 """The `command` module provides :class:`Command`\s and
2 :class:`Argument`\s for defining commands.
9 class CommandExit (Exception):
11 return self.__class__.__name__
13 class Success (CommandExit):
16 class Failure (CommandExit):
19 class Command (object):
20 """One-line command description here.
22 >>> c = Command(name='test', help='An example Command.')
23 >>> status = c.run(NullQueue(), PrintQueue(), help=True) # doctest: +REPORT_UDIFF
29 help BOOL (bool) Print a help message.
35 def __init__(self, name, aliases=None, arguments=[], help=''):
39 self.aliases = aliases
41 Argument(name='help', type='bool', default=False, count=1,
42 callback=StoreValue(True), help='Print a help message.'),
46 def run(self, inqueue=None, outqueue=None, **kwargs):
47 """`Normalize inputs and handle <Argument help> before punting
53 outqueue = NullQueue()
55 params = self.handle_arguments(inqueue, outqueue, kwargs)
56 if params['help'] == True:
57 outqueue.put(self.help())
59 self._run(inqueue, outqueue, params)
60 except CommandExit, e:
61 if isinstance(e, Failure):
68 def _run(self, inqueue, outqueue, params):
69 """This is where the command-specific magic will happen.
73 def handle_arguments(self, inqueue, outqueue, params):
74 """Normalize and validate input parameters (:class:`Argument` values).
76 for argument in self.arguments:
77 names = [argument.name] + argument.aliases
78 settings = [(name,v) for name,v in params.items() if name in names]
79 num_provided = len(settings)
81 if argument.optional == True or argument.count == 0:
82 settings = [(argument.name, argument.default)]
84 raise Failure('Required argument %s not set.'
87 raise Failure('Multiple settings for %s:\n %s'
89 '\n '.join(['%s: %s' % (name,value)
90 for name,value in sorted(settings)])))
91 name,value = settings[0]
92 if name != argument.name:
94 params[argument.name] = value
95 if argument.callback != None:
97 value = argument.callback(self, argument, value)
98 params[argument.name] = value
99 argument.validate(value)
102 def help(self, *args):
103 name_part = 'Command: %s' % self.name
104 if len(self.aliases) > 0:
105 name_part += ' (%s)' % ', '.join(self.aliases)
107 if len(self.arguments) > 0:
108 argument_part = ['Arguments:', '']
109 for a in self.arguments:
110 argument_part.append(textwrap.fill(
113 subsequent_indent=" "))
114 argument_part = '\n'.join(argument_part)
115 parts.append(argument_part)
116 parts.append(self._help) # help part
117 return '\n\n'.join(parts)
119 class Argument (object):
120 """Structured user input for :class:`Command`\s.
122 TODO: ranges for `count`?
124 def __init__(self, name, aliases=None, type='string', metavar=None,
125 default=None, optional=True, count=1,
126 completion_callback=None, callback=None, help=''):
130 self.aliases = aliases
133 metavar = type.upper()
134 self.metavar = metavar
135 self.default = default
136 self.optional = optional
138 self.completion_callback = completion_callback
139 self.callback = callback
143 return '<%s %s>' % (self.__class__.__name__, self.name)
146 return self.__str__()
149 parts = ['%s ' % self.name]
150 if self.metavar != None:
151 parts.append('%s ' % self.metavar)
152 parts.extend(['(%s) ' % self.type, self._help])
153 return ''.join(parts)
155 def validate(self, value):
156 """If `value` is not appropriate, raise `ValueError`.
158 pass # TODO: validation
160 # TODO: type conversion
162 # TODO: type extensions?
166 class StoreValue (object):
167 def __init__(self, value):
169 def __call__(self, command, argument, fragment=None):
172 class NullQueue (queue.Queue):
173 """The :class:`queue.Queue` equivalent of `/dev/null`.
175 This is a bottomless pit. Items go in, but never come out.
177 def get(self, block=True, timeout=None):
178 """Raise queue.Empty.
180 There's really no need to override the base Queue.get, but I
181 want to know if someone tries to read from a NullQueue. With
182 the default implementation they would just block silently
187 def put(self, item, block=True, timeout=None):
188 """Dump an item into the void.
190 Block and timeout are meaningless, because there is always a
191 free slot available in a bottomless pit.
195 class PrintQueue (NullQueue):
196 """Debugging :class:`NullQueue` that prints items before dropping
199 def put(self, item, block=True, timeout=None):
200 """Print `item` and then dump it into the void.
202 print 'ITEM:\n%s' % item