1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
|
# Authors:
# Jason Gerard DeRose <jderose@redhat.com>
#
# Copyright (C) 2008 Red Hat
# see file 'COPYING' for use and warranty information
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation; version 2 only
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""
Parameter system for command plugins.
"""
from types import NoneType
from plugable import ReadOnly, lock, check_name
from constants import NULLS, TYPE_ERROR, CALLABLE_ERROR
class DefaultFrom(ReadOnly):
"""
Derive a default value from other supplied values.
For example, say you wanted to create a default for the user's login from
the user's first and last names. It could be implemented like this:
>>> login = DefaultFrom(lambda first, last: first[0] + last)
>>> login(first='John', last='Doe')
'JDoe'
If you do not explicitly provide keys when you create a DefaultFrom
instance, the keys are implicitly derived from your callback by
inspecting ``callback.func_code.co_varnames``. The keys are available
through the ``DefaultFrom.keys`` instance attribute, like this:
>>> login.keys
('first', 'last')
The callback is available through the ``DefaultFrom.callback`` instance
attribute, like this:
>>> login.callback # doctest:+ELLIPSIS
<function <lambda> at 0x...>
>>> login.callback.func_code.co_varnames # The keys
('first', 'last')
The keys can be explicitly provided as optional positional arguments after
the callback. For example, this is equivalent to the ``login`` instance
above:
>>> login2 = DefaultFrom(lambda a, b: a[0] + b, 'first', 'last')
>>> login2.keys
('first', 'last')
>>> login2.callback.func_code.co_varnames # Not the keys
('a', 'b')
>>> login2(first='John', last='Doe')
'JDoe'
If any keys are missing when calling your DefaultFrom instance, your
callback is not called and None is returned. For example:
>>> login(first='John', lastname='Doe') is None
True
>>> login() is None
True
Any additional keys are simply ignored, like this:
>>> login(last='Doe', first='John', middle='Whatever')
'JDoe'
As above, because `DefaultFrom.__call__` takes only pure keyword
arguments, they can be supplied in any order.
Of course, the callback need not be a lambda expression. This third
example is equivalent to both the ``login`` and ``login2`` instances
above:
>>> def get_login(first, last):
... return first[0] + last
...
>>> login3 = DefaultFrom(get_login)
>>> login3.keys
('first', 'last')
>>> login3.callback.func_code.co_varnames
('first', 'last')
>>> login3(first='John', last='Doe')
'JDoe'
"""
def __init__(self, callback, *keys):
"""
:param callback: The callable to call when all keys are present.
:param keys: Optional keys used for source values.
"""
if not callable(callback):
raise TypeError(
CALLABLE_ERROR % ('callback', callback, type(callback))
)
self.callback = callback
if len(keys) == 0:
fc = callback.func_code
self.keys = fc.co_varnames[:fc.co_argcount]
else:
self.keys = keys
for key in self.keys:
if type(key) is not str:
raise TypeError(
TYPE_ERROR % ('keys', str, key, type(key))
)
lock(self)
def __call__(self, **kw):
"""
If all keys are present, calls the callback; otherwise returns None.
:param kw: The keyword arguments.
"""
vals = tuple(kw.get(k, None) for k in self.keys)
if None in vals:
return
try:
return self.callback(*vals)
except StandardError:
pass
def parse_param_spec(spec):
"""
Parse a param spec into to (name, kw).
The ``spec`` string determines the param name, whether the param is
required, and whether the param is multivalue according the following
syntax:
====== ===== ======== ==========
Spec Name Required Multivalue
====== ===== ======== ==========
'var' 'var' True False
'var?' 'var' False False
'var*' 'var' False True
'var+' 'var' True True
====== ===== ======== ==========
For example,
>>> parse_param_spec('login')
('login', {'required': True, 'multivalue': False})
>>> parse_param_spec('gecos?')
('gecos', {'required': False, 'multivalue': False})
>>> parse_param_spec('telephone_numbers*')
('telephone_numbers', {'required': False, 'multivalue': True})
>>> parse_param_spec('group+')
('group', {'required': True, 'multivalue': True})
:param spec: A spec string.
"""
if type(spec) is not str:
raise TypeError(
TYPE_ERROR % ('spec', str, spec, type(spec))
)
if len(spec) < 2:
raise ValueError(
'spec must be at least 2 characters; got %r' % spec
)
_map = {
'?': dict(required=False, multivalue=False),
'*': dict(required=False, multivalue=True),
'+': dict(required=True, multivalue=True),
}
end = spec[-1]
if end in _map:
return (spec[:-1], _map[end])
return (spec, dict(required=True, multivalue=False))
class Param(ReadOnly):
"""
Base class for all parameters.
"""
# This is a dummy type so that most of the functionality of Param can be
# unit tested directly without always creating a subclass; however, a real
# (direct) subclass must *always* override this class attribute:
type = NoneType # Ouch, this wont be very useful in the real world!
kwargs = (
('cli_name', str, None),
('doc', str, ''),
('required', bool, True),
('multivalue', bool, False),
('primary_key', bool, False),
('normalizer', callable, None),
('default_from', callable, None),
('flags', frozenset, frozenset()),
# The 'default' kwarg gets appended in Param.__init__():
# ('default', self.type, None),
)
def __init__(self, name, *rules, **kw):
# We keep these values to use in __repr__():
self.param_spec = name
self.__kw = dict(kw)
# Merge in kw from parse_param_spec():
if not ('required' in kw or 'multivalue' in kw):
(name, kw_from_spec) = parse_param_spec(name)
kw.update(kw_from_spec)
self.name = check_name(name)
self.nice = '%s(%r)' % (self.__class__.__name__, self.param_spec)
# Add 'default' to self.kwargs and makes sure no unknown kw were given:
assert type(self.type) is type
self.kwargs += (('default', self.type, None),)
if not set(t[0] for t in self.kwargs).issuperset(self.__kw):
extra = set(kw) - set(t[0] for t in self.kwargs)
raise TypeError(
'%s: takes no such kwargs: %s' % (self.nice,
', '.join(repr(k) for k in sorted(extra))
)
)
# Merge in default for 'cli_name' if not given:
if kw.get('cli_name', None) is None:
kw['cli_name'] = self.name
# Wrap 'default_from' in a DefaultFrom if not already:
df = kw.get('default_from', None)
if callable(df) and not isinstance(df, DefaultFrom):
kw['default_from'] = DefaultFrom(df)
# We keep this copy with merged values also to use when cloning:
self.__clonekw = kw
# Perform type validation on kw, add in class rules:
class_rules = []
for (key, kind, default) in self.kwargs:
value = kw.get(key, default)
if value is not None:
if kind is frozenset:
if type(value) in (list, tuple):
value = frozenset(value)
elif type(value) is str:
value = frozenset([value])
if (
type(kind) is type and type(value) is not kind
or
type(kind) is tuple and not isinstance(value, kind)
):
raise TypeError(
TYPE_ERROR % (key, kind, value, type(value))
)
elif kind is callable and not callable(value):
raise TypeError(
CALLABLE_ERROR % (key, value, type(value))
)
if hasattr(self, key):
raise ValueError('kwarg %r conflicts with attribute on %s' % (
key, self.__class__.__name__)
)
setattr(self, key, value)
rule_name = '_rule_%s' % key
if value is not None and hasattr(self, rule_name):
class_rules.append(getattr(self, rule_name))
check_name(self.cli_name)
# Check that all the rules are callable
self.class_rules = tuple(class_rules)
self.rules = rules
self.all_rules = self.class_rules + self.rules
for rule in self.all_rules:
if not callable(rule):
raise TypeError(
'%s: rules must be callable; got %r' % (self.nice, rule)
)
# And we're done.
lock(self)
def normalize(self, value):
"""
Normalize ``value`` using normalizer callback.
For example:
>>> param = Param('telephone',
... normalizer=lambda value: value.replace('.', '-')
... )
>>> param.normalize(u'800.123.4567')
u'800-123-4567'
If this `Param` instance was created with a normalizer callback and
``value`` is a unicode instance, the normalizer callback is called and
*its* return value is returned.
On the other hand, if this `Param` instance was *not* created with a
normalizer callback, if ``value`` is *not* a unicode instance, or if an
exception is caught when calling the normalizer callback, ``value`` is
returned unchanged.
:param value: A proposed value for this parameter.
"""
if self.normalizer is None:
return value
if self.multivalue:
if type(value) in (tuple, list):
return tuple(
self._normalize_scalar(v) for v in value
)
return (self._normalize_scalar(value),) # Return a tuple
return self._normalize_scalar(value)
def _normalize_scalar(self, value):
"""
Normalize a scalar value.
This method is called once for each value in a multivalue.
"""
if type(value) is not unicode:
return value
try:
return self.normalizer(value)
except StandardError:
return value
def convert(self, value):
"""
Convert ``value`` to the Python type required by this parameter.
For example:
>>> scalar = Str('my_scalar')
>>> scalar.type
<type 'unicode'>
>>> scalar.convert(43.2)
u'43.2'
(Note that `Str` is a subclass of `Param`.)
All values in `constants.NULLS` will be converted to None. For
example:
>>> scalar.convert(u'') is None # An empty string
True
>>> scalar.convert([]) is None # An empty list
True
Likewise, values in `constants.NULLS` will be filtered out of a
multivalue parameter. For example:
>>> multi = Str('my_multi', multivalue=True)
>>> multi.convert([True, '', 17, None, False])
(u'True', u'17', u'False')
>>> multi.convert([None, u'']) is None # Filters to an empty list
True
Lastly, multivalue parameters will always return a tuple (well,
assuming they don't return None as in the last example above).
For example:
>>> multi.convert(42) # Called with a scalar value
(u'42',)
>>> multi.convert([True, False]) # Called with a list value
(u'True', u'False')
Note that how values are converted (and from what types they will be
converted) completely depends upon how a subclass implements its
`Param._convert_scalar()` method. For example, see
`Str._convert_scalar()`.
:param value: A proposed value for this parameter.
"""
if value in NULLS:
return
if self.multivalue:
if type(value) not in (tuple, list):
value = (value,)
values = tuple(
self._convert_scalar(v, i) for (i, v) in filter(
lambda tup: tup[1] not in NULLS, enumerate(value)
)
)
if len(values) == 0:
return
return values
return self._convert_scalar(value)
def _convert_scalar(self, value, index=None):
"""
Implement in subclass.
"""
raise NotImplementedError(
'%s.%s()' % (self.__class__.__name__, '_convert_scalar')
)
class Bool(Param):
"""
"""
class Int(Param):
"""
"""
class Float(Param):
"""
"""
class Bytes(Param):
"""
"""
type = str
kwargs = Param.kwargs + (
('minlength', int, None),
('maxlength', int, None),
('length', int, None),
('pattern', str, None),
)
def __init__(self, name, **kw):
super(Bytes, self).__init__(name, **kw)
if not (
self.length is None or
(self.minlength is None and self.maxlength is None)
):
raise ValueError(
'%s: cannot mix length with minlength or maxlength' % self.nice
)
if self.minlength is not None and self.minlength < 1:
raise ValueError(
'%s: minlength must be >= 1; got %r' % (self.nice, self.minlength)
)
if self.maxlength is not None and self.maxlength < 1:
raise ValueError(
'%s: maxlength must be >= 1; got %r' % (self.nice, self.maxlength)
)
if None not in (self.minlength, self.maxlength):
if self.minlength > self.maxlength:
raise ValueError(
'%s: minlength > maxlength (minlength=%r, maxlength=%r)' % (
self.nice, self.minlength, self.maxlength)
)
elif self.minlength == self.maxlength:
raise ValueError(
'%s: minlength == maxlength; use length=%d instead' % (
self.nice, self.minlength)
)
def _rule_minlength(self, value):
"""
Check minlength constraint.
"""
if len(value) < self.minlength:
return 'Must be at least %(minlength)d bytes long.' % dict(
minlength=self.minlength,
)
def _rule_maxlength(self, value):
"""
Check maxlength constraint.
"""
if len(value) > self.maxlength:
return 'Can be at most %(maxlength)d bytes long.' % dict(
maxlength=self.maxlength,
)
def _rule_length(self, value):
"""
Check length constraint.
"""
if len(value) != self.length:
return 'Must be exactly %(length)d bytes long.' % dict(
length=self.length,
)
class Str(Bytes):
"""
"""
type = unicode
kwargs = Bytes.kwargs[:-1] + (
('pattern', unicode, None),
)
def __init__(self, name, **kw):
super(Str, self).__init__(name, **kw)
def _convert_scalar(self, value, index=None):
if type(value) in (self.type, int, float, bool):
return self.type(value)
raise TypeError(
'Can only implicitly convert int, float, or bool; got %r' % value
)
|