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
|
# -*- coding: utf-8 -*-
# Copyright (c) 2010 Mark Sandstrom
# Copyright (c) 2011-2015 Raphaël Barrois
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import logging
logger = logging.getLogger(__name__)
from . import declarations
from . import errors
from . import utils
class LazyStub(object):
"""A generic container that only allows getting attributes.
Attributes are set at instantiation time, values are computed lazily.
Attributes:
__initialized (bool): whether this object's __init__ as run. If set,
setting any attribute will be prevented.
__attrs (dict): maps attribute name to their declaration
__values (dict): maps attribute name to computed value
__pending (str list): names of the attributes whose value is being
computed. This allows to detect cyclic lazy attribute definition.
__containers (LazyStub list): "parents" of the LazyStub being built.
This allows to have the field of a field depend on the value of
another field
__model_class (type): the model class to build.
"""
__initialized = False
def __init__(self, attrs, containers=(), model_class=object, log_ctx=None):
self.__attrs = attrs
self.__values = {}
self.__pending = []
self.__containers = containers
self.__model_class = model_class
self.__log_ctx = log_ctx or '%s.%s' % (model_class.__module__, model_class.__name__)
self.factory_parent = containers[0] if containers else None
self.__initialized = True
def __repr__(self):
return '<LazyStub for %s.%s>' % (self.__model_class.__module__, self.__model_class.__name__)
def __str__(self):
return '<LazyStub for %s with %s>' % (
self.__model_class.__name__, list(self.__attrs.keys()))
def __fill__(self):
"""Fill this LazyStub, computing values of all defined attributes.
Retunrs:
dict: map of attribute name => computed value
"""
res = {}
logger.debug("LazyStub: Computing values for %s(%s)",
self.__log_ctx, utils.log_pprint(kwargs=self.__attrs),
)
for attr in self.__attrs:
res[attr] = getattr(self, attr)
logger.debug("LazyStub: Computed values, got %s(%s)",
self.__log_ctx, utils.log_pprint(kwargs=res),
)
return res
def __getattr__(self, name):
"""Retrieve an attribute's value.
This will compute it if needed, unless it is already on the list of
attributes being computed.
"""
if name in self.__pending:
raise errors.CyclicDefinitionError(
"Cyclic lazy attribute definition for %s; cycle found in %r." %
(name, self.__pending))
elif name in self.__values:
return self.__values[name]
elif name in self.__attrs:
val = self.__attrs[name]
if isinstance(val, LazyValue):
self.__pending.append(name)
val = val.evaluate(self, self.__containers)
last = self.__pending.pop()
assert name == last
self.__values[name] = val
return val
else:
raise AttributeError(
"The parameter %s is unknown. Evaluated attributes are %r, "
"definitions are %r." % (name, self.__values, self.__attrs))
def __setattr__(self, name, value):
"""Prevent setting attributes once __init__ is done."""
if not self.__initialized:
return super(LazyStub, self).__setattr__(name, value)
else:
raise AttributeError('Setting of object attributes is not allowed')
class LazyValue(object):
"""Some kind of "lazy evaluating" object."""
def evaluate(self, obj, containers=()): # pragma: no cover
"""Compute the value, using the given object."""
raise NotImplementedError("This is an abstract method.")
class OrderedDeclarationWrapper(LazyValue):
"""Lazy wrapper around an OrderedDeclaration.
Attributes:
declaration (declarations.OrderedDeclaration): the OrderedDeclaration
being wrapped
sequence (int): the sequence counter to use when evaluatin the
declaration
"""
def __init__(self, declaration, sequence, create, extra=None, **kwargs):
super(OrderedDeclarationWrapper, self).__init__(**kwargs)
self.declaration = declaration
self.sequence = sequence
self.create = create
self.extra = extra
def evaluate(self, obj, containers=()):
"""Lazily evaluate the attached OrderedDeclaration.
Args:
obj (LazyStub): the object being built
containers (object list): the chain of containers of the object
being built, its immediate holder being first.
"""
return self.declaration.evaluate(self.sequence, obj,
create=self.create,
extra=self.extra,
containers=containers,
)
def __repr__(self):
return '<%s for %r>' % (self.__class__.__name__, self.declaration)
class AttributeBuilder(object):
"""Builds attributes from a factory and extra data.
Attributes:
factory (base.Factory): the Factory for which attributes are being
built
_attrs (DeclarationDict): the attribute declarations for the factory
_subfields (dict): dict mapping an attribute name to a dict of
overridden default values for the related SubFactory.
"""
def __init__(self, factory, extra=None, log_ctx=None, **kwargs):
super(AttributeBuilder, self).__init__(**kwargs)
if not extra:
extra = {}
self.factory = factory
self._containers = extra.pop('__containers', ())
self._attrs = factory.declarations(extra)
self._log_ctx = log_ctx
initial_declarations = factory.declarations({})
attrs_with_subfields = [
k for k, v in initial_declarations.items()
if self.has_subfields(v)]
self._subfields = utils.multi_extract_dict(
attrs_with_subfields, self._attrs)
def has_subfields(self, value):
return isinstance(value, declarations.ParameteredAttribute)
def build(self, create, force_sequence=None):
"""Build a dictionary of attributes.
Args:
create (bool): whether to 'build' or 'create' the subfactories.
force_sequence (int or None): if set to an int, use this value for
the sequence counter; don't advance the related counter.
"""
# Setup factory sequence.
if force_sequence is None:
sequence = self.factory._generate_next_sequence()
else:
sequence = force_sequence
# Parse attribute declarations, wrapping SubFactory and
# OrderedDeclaration.
wrapped_attrs = {}
for k, v in self._attrs.items():
if isinstance(v, declarations.OrderedDeclaration):
v = OrderedDeclarationWrapper(v,
sequence=sequence,
create=create,
extra=self._subfields.get(k, {}),
)
wrapped_attrs[k] = v
stub = LazyStub(wrapped_attrs, containers=self._containers,
model_class=self.factory, log_ctx=self._log_ctx)
return stub.__fill__()
class StubObject(object):
"""A generic container."""
pass
|