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
|
"""
Proxy a configuration value. Defers the lookup until the value is used, so that
values can be read statically at import time.
"""
import functools
import operator
from typing import Any
from typing import Callable
from typing import cast
from typing import Type
from typing import TypeVar
from typing import TYPE_CHECKING
from staticconf import errors
from staticconf.validation import Validator
if TYPE_CHECKING:
from staticconf.config import ConfigNamespace
class UndefTokenType:
"""A token to represent an undefined value, so that None can be used
as a default value.
"""
def __repr__(self) -> str:
return "<Undefined>"
UndefToken = UndefTokenType()
_special_names = [
'__abs__', '__add__', '__and__', '__bool__', '__call__', '__cmp__',
'__coerce__',
'__contains__', '__delitem__', '__delslice__', '__div__', '__divmod__',
'__eq__', '__float__', '__floordiv__', '__ge__', '__getitem__',
'__getslice__', '__gt__', '__hash__', '__hex__', '__iadd__', '__iand__',
'__idiv__', '__idivmod__', '__ifloordiv__', '__ilshift__', '__imod__',
'__imul__', '__int__', '__invert__', '__ior__', '__ipow__', '__irshift__',
'__isub__', '__iter__', '__itruediv__', '__ixor__', '__le__', '__len__',
'__long__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__',
'__neg__', '__oct__', '__or__', '__pos__', '__pow__', '__radd__',
'__rand__', '__rdiv__', '__rdivmod__',
'__repr__', '__reversed__', '__rfloorfiv__', '__rlshift__', '__rmod__',
'__rmul__', '__ror__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__',
'__rtruediv__', '__rxor__', '__setitem__', '__setslice__', '__sub__',
'__truediv__', '__xor__', 'next', '__nonzero__', '__str__', '__unicode__',
'__index__', '__fspath__',
]
def identity(x: Any) -> Any:
return x
unary_funcs = {
'__unicode__': cast(Callable[[Any], Any], str),
'__str__': cast(Callable[[Any], Any], str),
'__fspath__': identity, # python3.6+ os.PathLike interface
'__repr__': cast(Callable[[Any], Any], repr),
'__nonzero__': cast(Callable[[Any], Any], bool), # Python2 bool
'__bool__': cast(Callable[[Any], Any], bool), # Python3 bool
'__hash__': cast(Callable[[Any], Any], hash),
}
def build_class_def(cls: Type["ValueProxy"]) -> type:
def build_method(name: str) -> Callable[["ValueProxy", Any, Any], Any]:
def method(self: "ValueProxy", *args: Any, **kwargs: Any) -> Any:
if name in unary_funcs:
return unary_funcs[name](self.value)
if hasattr(operator, name):
return getattr(operator, name)(self.value, *args)
return getattr(self.value, name)(*args, **kwargs)
return method
namespace = {name: build_method(name) for name in _special_names}
return type(cls.__name__, (cls,), namespace)
F = TypeVar("F", bound=Callable[..., Any])
def cache_as_field(cache_name: str) -> Callable[[F], F]:
"""Cache a functions return value as the field 'cache_name'."""
def cache_wrapper(func: F) -> F:
@functools.wraps(func)
def inner_wrapper(self: object, *args: Any, **kwargs: Any) -> Any:
value = getattr(self, cache_name, UndefToken)
if value != UndefToken:
return value
ret = func(self, *args, **kwargs)
setattr(self, cache_name, ret)
return ret
return cast(F, inner_wrapper)
return cache_wrapper
def extract_value(proxy: "ValueProxy") -> Any:
"""Given a value proxy type, Retrieve a value from a namespace, raising
exception if no value is found, or the value does not validate.
"""
value = proxy.namespace.get(proxy.config_key, proxy.default)
if value is UndefToken:
raise errors.ConfigurationError("%s is missing value for: %s" %
(proxy.namespace, proxy.config_key))
try:
return proxy.validator(value)
except errors.ValidationError as e:
raise errors.ConfigurationError("%s failed to validate %s: %s" %
(proxy.namespace, proxy.config_key, e))
class ValueProxy:
"""Proxy a configuration value so it can be loaded after import time."""
__slots__ = [
'validator',
'config_key',
'default',
'_value',
'namespace',
'__weakref__'
]
@classmethod
@cache_as_field('_class_def')
def get_class_def(cls) -> type:
return build_class_def(cls)
def __new__(cls, *args: Any, **kwargs: Any) -> "ValueProxy":
"""Create instances of this class with proxied special names."""
klass = cast(Type["ValueProxy"], cls.get_class_def())
instance = cast("ValueProxy", object.__new__(klass))
klass.__init__(instance, *args, **kwargs)
return instance
def __init__(
self,
validator: Validator,
namespace: "ConfigNamespace",
key: str,
default: Any = UndefToken,
) -> None:
self.validator = validator
self.config_key = key
self.default = default
self.namespace = namespace
self._value = UndefToken
@cache_as_field('_value')
def get_value(self) -> Any:
return extract_value(self)
value = property(get_value)
def __getattr__(self, item: str) -> Any:
return getattr(self.value, item)
def reset(self) -> None:
"""Clear the cached value so that configuration can be reloaded."""
self._value = UndefToken
|
