Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/attr/converters.py: 28%

1# SPDX-License-Identifier: MIT 

2 

3""" 

4Commonly useful converters. 

5""" 

6 

7 

8import typing 

9 

10from ._compat import _AnnotationExtractor 

11from ._make import NOTHING, Factory, pipe 

12 

13 

14__all__ = [ 

15 "default_if_none", 

16 "optional", 

17 "pipe", 

18 "to_bool", 

19] 

20 

21 

22def optional(converter): 

23 """ 

24 A converter that allows an attribute to be optional. An optional attribute 

25 is one which can be set to ``None``. 

26 

27 Type annotations will be inferred from the wrapped converter's, if it 

28 has any. 

29 

30 :param callable converter: the converter that is used for non-``None`` 

31 values. 

32 

33 .. versionadded:: 17.1.0 

34 """ 

35 

36 def optional_converter(val): 

37 if val is None: 

38 return None 

39 return converter(val) 

40 

41 xtr = _AnnotationExtractor(converter) 

42 

43 t = xtr.get_first_param_type() 

44 if t: 

45 optional_converter.__annotations__["val"] = typing.Optional[t] 

46 

47 rt = xtr.get_return_type() 

48 if rt: 

49 optional_converter.__annotations__["return"] = typing.Optional[rt] 

50 

51 return optional_converter 

52 

53 

54def default_if_none(default=NOTHING, factory=None): 

55 """ 

56 A converter that allows to replace ``None`` values by *default* or the 

57 result of *factory*. 

58 

59 :param default: Value to be used if ``None`` is passed. Passing an instance 

60 of `attrs.Factory` is supported, however the ``takes_self`` option 

61 is *not*. 

62 :param callable factory: A callable that takes no parameters whose result 

63 is used if ``None`` is passed. 

64 

65 :raises TypeError: If **neither** *default* or *factory* is passed. 

66 :raises TypeError: If **both** *default* and *factory* are passed. 

67 :raises ValueError: If an instance of `attrs.Factory` is passed with 

68 ``takes_self=True``. 

69 

70 .. versionadded:: 18.2.0 

71 """ 

72 if default is NOTHING and factory is None: 

73 raise TypeError("Must pass either `default` or `factory`.") 

74 

75 if default is not NOTHING and factory is not None: 

76 raise TypeError( 

77 "Must pass either `default` or `factory` but not both." 

78 ) 

79 

80 if factory is not None: 

81 default = Factory(factory) 

82 

83 if isinstance(default, Factory): 

84 if default.takes_self: 

85 raise ValueError( 

86 "`takes_self` is not supported by default_if_none." 

87 ) 

88 

89 def default_if_none_converter(val): 

90 if val is not None: 

91 return val 

92 

93 return default.factory() 

94 

95 else: 

96 

97 def default_if_none_converter(val): 

98 if val is not None: 

99 return val 

100 

101 return default 

102 

103 return default_if_none_converter 

104 

105 

106def to_bool(val): 

107 """ 

108 Convert "boolean" strings (e.g., from env. vars.) to real booleans. 

109 

110 Values mapping to :code:`True`: 

111 

112 - :code:`True` 

113 - :code:`"true"` / :code:`"t"` 

114 - :code:`"yes"` / :code:`"y"` 

115 - :code:`"on"` 

116 - :code:`"1"` 

117 - :code:`1` 

118 

119 Values mapping to :code:`False`: 

120 

121 - :code:`False` 

122 - :code:`"false"` / :code:`"f"` 

123 - :code:`"no"` / :code:`"n"` 

124 - :code:`"off"` 

125 - :code:`"0"` 

126 - :code:`0` 

127 

128 :raises ValueError: for any other value. 

129 

130 .. versionadded:: 21.3.0 

131 """ 

132 if isinstance(val, str): 

133 val = val.lower() 

134 truthy = {True, "true", "t", "yes", "y", "on", "1", 1} 

135 falsy = {False, "false", "f", "no", "n", "off", "0", 0} 

136 try: 

137 if val in truthy: 

138 return True 

139 if val in falsy: 

140 return False 

141 except TypeError: 

142 # Raised when "val" is not hashable (e.g., lists) 

143 pass 

144 raise ValueError(f"Cannot convert value to bool: {val}")